KEK—90-1
JP9103115
KEK Report 90- 1 April 1990 H
Proceedings of the Workshop on Intensity Frontier Physics
April 3 and 4, 1989 KEK, Tsukuba, Japan
Edited by T. SATO, KEK
NATIONAL LABORATORY FOR HIGH ENERGY PHYSICS © National Laboratory for High Energy Physics, 1990 KEK Reports are available from: Technical Information & Library National Laboratory for High Energy Physics 1-1 Oho, Tsukuba-shi Ibaraki-ken, 303 JAPAN Phone: 0298-64-1171 Telex: 3652-534 (Domestic) (0)3652-534 (International) Fax: 0298-64-4604 Cable: KEKOHO Preface
The Workshop on Intensity Frontier Physics was held on April 3rd and 4th at KEK.
The KAON project ( Kaon, Antiproton, Other hadrons, Neutrino ) has been proposed by TRIUMF. Canada. The JHP ( Japanese Hadron Project ) has been also proposed by INS in Japan. Both projects intend to explore intensity frontiers of science by means of intense hadron beams. The JHP and the KAON are complementary to each other in many aspects, and the constructive collaborations should be very important for both sides.
The main purpose of thie workshop was to discuss physics interests, various aspects of new techniques and possible collaborations in these projects.
It was attended by about 90 participants including 7 physicists from
Canada. There were various discussions on physics, new techniques on accelerators and beamlines, and the possible collaborations.
T. Sato, KEK
Organizers of the Workshop
H. Bando ( Fukui Univ. ), H. Ejiri ( Osaka Univ. ), T. Fukuda ( INS ),
D. Gill ( TRIUMF ), P. Kitching ( TRIUMF ), T. Sato ( KEK ) WORKSHOP on INTENSITY FRONTIER PHYSICS JAPAN/CANADA
April 3 and 4, 1989 . at KEK (Tsukuba, Ibaraki, Japan)
PROGRAM Session I April 3rd : 9:30 - 10:30 Introduction Chair person H. Ejiri (Osaka Univ.) Introduction to the High Intensity Facilities T. Yamazaki (INS) The Jap anese Hadron Project(JHP) M. Craddock (TRIUMF) The KAON Factory
Tea , Coffee and Lunch 10:30 - 12:40 (Tour to KEK Counter Experimental Hall)
Session II 12:40 - 14:30 Particle Physics I Discussion Leader Y. Nagashima (Osaka Univ.) 2.1 S. Lim(KEK) K Rare Decays 2.2 J. Ng(TRIUMF) Particle Theory 2.3 D. Bryman (TRIUMF) Particle Physics at the KAON Session III 14:30 - 16:00 Particle Physics II Discussion Leader T. Sato (KEK) 3.1 T. Inagaki (KEK) K -^e Experiment 3.2 N. Sasao (Kyoto Univ.) K -*7i;ee Experiment 3.3 T. Taniguchi (KEK) Fast Electronics
Tea and Coffee Break 16:00 - 16:30 Session IV 16:30 - 19:00 Accelerators and Beam Lines Discussion Leader M. Kihara (KEK) 4.1 M.K. Craddock (TRIUMF) The KAON Factory Accelerators 4.2 Y. Kamiya (KEK) JHP Accelerators 4.3 D. Gill (TRIUMF) Exp. Areas and Beam Lines at the KAON 4.4 K.H. Tanaka (KEK) KEK Beam Lines and Intense Beam Handling 4.5 Discussions on the KAON
Reception 19:30 - 20:30
Session V April 4th 9:30 - 10:40 Nuclear Physics I Discussion Leader D. Gill (TRIUMF) 5.1 P. Kitching (TRIUMF) Nuclear Physics at the KAON 5.2 T. Fukuda (INS) Nuclear Physics at the JHP K-Arena
Tea and Coffee Break 10:40 - 11:00
Session VI 11:00 - 12:40 Nuclear Physics II Discussion Leader H. Toki (Tokyo Metropolitan Univ.) 6.1 H. Bando (Fukui Univ.) Flavor Nuclear Physics Theory 6.2 T. Kishimoto (Osaka Univ.) Strangeness Nuclear Physics 6.3 T. Kobayashi (KEK) Double Charge Exchange reactions
Lunch 12:40 - 14:00
Session VII 14:00 - 15:00 Exotics Discussion Leader K. Imai (Kyoto Univ.) 7.1 A. Masaike (Kyoto Univ.) Spin Physics and p Physics 7.2 T. Tsuru (KEK) Experiments on Exotic States 7.3 J. Imazato (KEK) Muon Polarization in KfJ.2 7.4 Y. Yamaguchi (Tokai Univ.) Dynamic CP Violation Tea and Coffee Break 15:00 - 15:20
Session VIII 15:20 - 16:20 Open Discussion on Japan/Canada Collaborations Discussion Leader K. Nakai (KEK) D. Gill (TRIUMF) J. D'Auria (TRIUMF) Y. Nagashima (Osaka Univ.) K. Imai (Kyoto Univ.) Session DC ' 16:20 -17:00 Concluding Remarks Chair person M.K. Craddock (TRIUMF) 9.1 H. Ejiri (Osaka Univ.) 9.2 E. Vogt (TRIUMF) CONTENTS page
1. The TRIUMF KAON Factory - An Overview H. K. Craddock, TRIUHF 1
2. Particle Theory and Intense Hadron J. N. Ng. TRIUMF 9
Facilities - An Overview
3. Particle Physics Prospects for D. Bryman, TRIUHF 21
the KAON Factory
4. The Status of E137 at KEK T. Inagaki, KEK 33
An Experiment to Search for
KL — Jte and ee
5. The TRIUMF KAON Factory Accelerators M. K. Craddock, TRIUMF 43
6. Experimental Facilities for KAON D. R. Gill, TRIUMF 52
7. KEK - PS Beam Channels at Present K. H. Tanaka. KEK 64
and New Experimental Halls
8. Nuclear Physics at the KAON Factory P. Kitching. TRIUMF 68
9. Nuclear Physics at the JHP K Arena T. Fukuda, INS 85
10. Weak Decay of A Hypernuclei T. Kishimoto, Osaka Univ. 92
11. Pion-induced Double Charge Exchange T. Kobayashi, KEK 105
Reactions for studying a Soft Giant
Dipole Resonance of Light Neutron-
Dripline Nuclei
12. Search for Double Hypernuclei and K. Inai, Kyoto Univ. 109
H-Dibaryon
13. Physics with Polarized Hyperons and A. Masaike, Kyoto Univ. 116
Low Energy Antiprotons at KAON Factory
14. Precise Measurement of p.* Polarization J. Imazato, KEK 135
in the Decay of K*-> p. * + v IS. Dynamical CP Violation Y. Yamaguchi, Tokai Univ. 146
IB. From the KEK-PS to the KAON Factory K. Nakai et. al., KEK 148
A Bridge to a New Era of KAON Physics
17. Discussion of Participation D. R. Gili, TRIUMF 159
Possibilities at KEK
18. Radioactive Beams and Intense J.M.D'Auria, Simon Fraser Univ. 163
Pulsed Neutron Beams
19. Intensity Frontier Physics H. Ejiri, Osaka Univ. 174
Particle and Nuclear Physics Frontiers
Explored by High Intensity Probes
20. Concluding Remarks E. Vogt, TRIUMF 187 THE TRIUMF KAON FACTORY - AN OVERVIEW M.K. Craddock* TRIUMF, 4004 Wesbrook Mall, Vancouver, B.C. V6T 2A3 Summary
TRIUMF has been awarded $11M for a one-year pre-construction Engineering Design and Impact Study of the KAON Factory. This will enable prototypes of many accelerator components to be built and the design of the accelerators and the layout of the experimental areas to be reviewed. The building and tunnel designs will be finalized, environmental, legal and economic impact studies carried out, and international involvement pursued further.
Introduction
The TRIUMF Kaon-Antiproton-Otherhadron-Neutrino Factory has been described in full in the original proposal1. The basic aim is to accelerate a 100 /xA beam of pro tons to 30 GeV, roughly 100 times more than available at present. This would provide correspondingly more intense - or pure - beams of secondary particles (kaons, pions, muons, antinucleons, hyperons and neutrinos) for particle and nuclear physics studies on the "precision frontier", complementary to the "energy frontier". Major areas of investigation would be
• rare decay modes of kaons and hyperons
• CP violation
• meson and baryon spectroscopy
• meson and baryon interactions
• neutrino scattering and oscillations
• quark structure of nuclei
• properties of hypernuclei
• K+ and p scattering from nuclei.
Experience with the pion factories has already shown how high beam intensities make it possible to explore the "precision frontier" with results complementary to those achievable at the "energy frontier". A notable example was the setting of a lower limit of 380 GeV on the mass of any right-handed W-boson by a muon decay "On leave from Physics Department, University of British Columbia. measurement2 at TRIUMF in 19S2. Others include improved confirmation of muon- electron universality and the first observations of the muonium Lamb shift and of the breakdown of charge symmetry in neutron-proton scattering. For kaon decay Figure 1 illustrates the improved branching ratios attainable for selected channels, pushing up the mass limits on various exotic particles. A
Ki-irVe K*-»*» K-lv Ki-T*,0 i-5 - 10 1985
io-*H
2 10"7 A UNDER WAY i- < <9 I0"a J_ 2 K-FACT0RY | 10 "9 -J T < OC
00 10-I0_| THEORY T -II 10 T io-,2H
lo"13-.
Fig. 1. Branching ratios for selected kaon decay channels showing limits attainable with a KAON Factory. comprehensive justification of the physics case for K factories may be found in the three proposals so far published1'3'"1 and in the proceedings of the recent international conferences at Mainz5, Lake Louise6 and Rockport7. Papers summarizing the physics case are given later in these proceedings by Ng8 (particle physics), Bryman9 (rare decays) and Kitching10 (nuclear physics). To obtain the most up-to-date assessment a number of workshops have been organized by TRIUMF this year on KAON Factory physics topics - and are listed in Table I. Table I. KAON Factory Workshops
Topic Location Date
Rare Kaon Decays TRIUMF Nov 30-Dec 3 1988 and CP violation Spin Physics TRIUMF Feb 15-16 19S9 Hadron Spectroscopy TRIUMF Feb 20-21 19S9 Neutrino Physics Montreal May 14 1989 Physics at the KAON Factory Bad Honnef, June 7-9 19S9 W. Germany Hypernuclear Physics at the KEK, Japan June 17-18 1989 KAON Factory Spin and Symmetries TRIUMF June 30-Jul 2 1989 Users Workshop TRIUMF July 10-11 19S9 Low Energy Muon Science TRIUMF July 19-21 1989 at Large Accelerators Intense Hadron Sources Turin, Italy Oct 1S-20 1989 and Antiproton Physics
Accelerator Design
The TRIUMF H~ cyclotron, which routinely delivers 150 /*A beams at 500 MeV, would provide a ready-made and reliable injector. It would be followed by two fast- cycling synchrotrons interleaved with 3 storage rings, as follows: A Accumulator: accumulates cw 450 MeV beam from the cyclotron over 20 ms periods B Booster: 50 Hz synchrotron; accelerates beam to 3 GeV; circumference 214 m C Collector: collects 5 Booster pulses and manipulates longitudinal emit tance D Driver: main 10 Hz synchrotron; accelerates beam to 30 GeV; circum ference 1072 m E Extender: 30 GeV stretcher ring for slow extraction for coincidence experiments This arrangement allows the B and D rings to run continuous acceleration cycles without flat bottoms or flat tops. The use of a Booster permits a smaller normalized emittance and hence reduces the aperture and cost of the Driver magnets for a given space charge tune shift. The use of a Booster also simplifies the rf design by separating the requirements for large frequency swing and high voltage (33% and 600 kV respectively for the Booster, and 3% and 2550 kV for the Driver). These high rf voltages are associated with the high cycling rates; the use of an asymmetric magnet cycle with a rise 3 times longer than the fall in the Driver reduces the voltage required by one-third, and the number of cavities in proportion. In the Booster the saving is less because more voltage is needed for bucket creation. Figure 2 shows a proposed site layout together with cross-sections through the tunnels, with the Accumulator above the Booster in the small tunnel, and the Col lector and Extender rings above and below the Driver in the main tunnel. Identical lattices and tunes are used for the rings in each tunnel. This is a natural choice pro viding structural simplicity, similar magnet apertures and straightforward matching for beam transfer. Further details of accelerator design and prototype construction are given in a separate paper in these proceedings.11 BOOSTER MAIN TUNNEL
EXPERIMENTAL HALL Fig. 2. Possible site layout together with cross sections through the tunnels
Experimental Areas and Targets
The revised experimental area layout proposed by Doornbos and Beveridge12 (Fig. 3) is summarized later in these proceedings by Gill.13 The slow extracted proton beam will be shared between two lines each with two production targets. Each target will feed at least two forward K and p channels, and in some cases backward /* channels. A dedicated line and area is provided for polarized proton beams and the neutrino production target and area are now incorporated in the main hall for better crane access. Target development includes both modification of an existing rotating graphite target (driven and cooled by water) for tungsten, and the construction of a prototype target rotated by a flexible cooling line.
-4- K° AREA
KAON FACTORY ' • EXPERIMENTAL AREA Fig. 3. Proposed experimental area layout.
Status of the Project
Following technically favourable reviews of the proposal by the funding agencies, the governments of Canada and British Columbia in 1987 instituted supplementary studies on economic benefits, broader national management (the four founding uni versities have now been joined by the Universities of Manitoba, Montreal, Regina and Toronto) and international involvement. Exploratory discussions abroad at the end of 19S7 (see below) indicated a potential for ~$200M (Cdn) in international contri butions - about one third of the total cost of S571M. Furthermore the Province of British Columbia has given approval in principle to the funding of the buildings and tunnels ($92M). The most recent development has been the joint funding by the federal and provin cial governments of an SllM pre-construction Engineering Design and Impact Study. This began in October 19SS and is planned to take 15 months. It will enable pro totypes of the major components to be built, the cost estimates to be updated, the international contributions to be better defined and various impact studies to be car ried out. The various projects are listed below, together with the names of the group leaders and other engineers and physicists involved.
-5 — Project Leader A. Astbury Accelerator Design M.K. Craddock; R. Baartman, S. Koscielniak, G.H. Mackenzie, J.R. Richardson, R.V. Servranckx and U. Wienands Systems Integration E.W. Blackmore; G. Clark, M. Zanolli (CERN) RF Systems R. Poirier; R. Burge, T. Enegren Magnets A.J. Otter; C. Haddock, P. Schwandt (IUCF) Magnet Power Supplies K. Reiniger; Beam Pipe & Vacuum C.J. Oram Kickers G. Wait; M. Barnes Controls D. Dohan; W.K. Dawson, B. Frammery (CERN), D. Schultz (LANL) Shielding & Safety I.M. Thorson; D. Axen (U.B.C.) Cyclotron Beam Extraction M. Zach; G- Dutto, R.E. Laxdal, J. Pearson Experimental Areas J. Beveridge; J. Doombos, G. Stinson Targets T.A. Hodges Science Workshops P. Kitching (Univ. of Alberta) International Consultations P. Dyne (ISTC); E.W. Vogt Project Management G. Ritchie; G. Ridout (UMA Spantec Ltd); V.K. Verma Building Design Company to be appointed Tunnel Design Company to be appointed Services & Power Company to be appointed Industry Development D. Williams; A. Stretch (Monenco Ltd.); J. Carey Economic Assessment Company to be appointed Legal Studies Company to be appointed Environmental Studies Company to be appointed International Consultations
A Canadian delegation visited West Germany, Italy, Japan and the U.S.A. in late 19S7 to explore the potential for international participation in the KAON Factory. Each country agreed to consider supplying components for construction, and indeed the possibility of support is being explicitly allowed for in the planning scenarios of both Germany and Italy. In the U.S.A. the DOE and NSF requested advice from NSAC, which set up a subcommittee under Prof. H. Feshbach. This has recently completed its report, which characterizes the Canadian proposal as "a conservative design" and "cost-effective". In all it appears that there is a potential for about $200M (Cdn) - or one-third of the total cost - in international contributions. Besides the countries mentioned above, Belgium, Britain, France, Israel and the People's Republic of China have all expressed interest in participating in experiments and in some cases in accelerator design and construction. International consultations will now continue more formally under the aegis of the pre-construction study with a first
-6- round of visits scheduled for April and May 1989 to begin identifying suitable items to be supplied. E.W. Vogt's paper14 at the end of these proceedings will give more details of these initiatives.
Conclusion
The pre-construction Engineering Design and Impact Study now under way, funded by the Canadian federal and provincial governments, is a wide-ranging one intended to cover all aspects of the project - scientific, engineering, environmental, legal and economic - including international involvement. It is expected to be com plete by the end of 1989, leaving the way clear for final approval of the project in 1990. TRIUMF has benefitted from a long history of collaboration with Japanese scien tists and institutions. It has gained not only from the experience brought to Canada by Japanese individuals, but also from direct contributions of hardware — most re cently a long superconducting solenoid for an improved muon channel. We attempt to run a user-frien *.ly laboratory and certainly hope that Japanese scientists experience comparable benefits in working at TRIUMF. For the future, the Japanese Hadron Project and the TRIUMF KAON Factory - even though they are largely complemen tary - clearly offer enhanced opportunities for collaboration to our mutual benefit (Gill15, D'Auria16).
References
1. KAON Factory Proposal, TRIUMF (19S5). 2. J. Carr et al., Phys. Rev. Lett., 51, 627 (1983). 3. A proposal to extend the intensity frontier of nuclear and particle physics to 45 GeV (LAMPF H), LA-UR-S4-3982 (1984). The physics and a plan for a 45 GeV facility that extends the high-intensity capability in nuclear and particle physics, LA-10720-MS (1986). 4. Proposal for a European Hadron Facility, EHF 87-18 (1987). 5. Proc. Intl. Conf. on a European Hadron Facility, Mainz, ed. Th. Walcher (North Holland, 1987). 6. Proc. 2nd Conf. on Intersections between Particle and Nuclear Physics, Lake Louise, May 1985, ed. D.F. Geesaman, AIP Conf. Proc., 150 (1986). 7. Proc. 3rd Conf. on Intersections between Particle and Nuclear Physics, Rock- port, May 1988, ed. G.M. Bunce, AIP Conf. Proc. 176 (1989). 8. J.N. Ng, "Particle theory and intense hadron facilities - an overview", (these proceedings). 9. D.A. Bryman, "Particle physics prospects for the KAON Factory", ibid.
-7- 10. P. Kitching, "Nuclear physics at the KAON Factory", ibid. 11. M.K. Craddock, "The TRIUMF KAON Factory accelerators", ibid. 12. J. Doornbos & J. Beveridge, "Layout of secondary beams at KAON", TRI-DN- S9-K19. 13. D.R. Gill, "Experimental facilities for KAON", (these proceedings). 14. E.W. Vogt, "Concluding remarks", ibid.. 15. D.R. Gill, "Discussion of participation possibilities at KEK", ibid. 16. J.M. D'Auria, "Radioactive beams and intense pulsed neutron beams: research areas for Japanese/Canadian collaboration at JHP", ibid.
-8- PARTICLE THEORY AND INTENSE HADRON FACILITIES - AN OVERVIEW - John N. Ng Theory Group. TRIUMF, 4004 Wesbrook Mall, Vancouver, B.C. V6T 2A3
Abstract
A brief overview of particle physics that can be done at an intensive hadron facility (IHF) is given. The emphasis is placed on testing the standard model, light Higgs boson searches and CP violation, which are areas an IHF can do especially well.
Introduction
In this brief overview of particle theory I will emphasize those aspects which are most relevant to intensity hadron facilities (IHF) such as KAON and the Japanese Hadron Physics (JHP) facility. A central theme will be to illustrate the importance of IHF in determining the unknown parameters in the Kobayashi- Maskawa (KM) quark mixing matrix1,2, the study of CP violation3, and the search of light Higgs-like boson4,5. New physics can be discovered through the search for lepton flavor violating decays such as IY'° —* [ie, K\ —+ izy.e. as well as looking for deviations from the standard model predictions of rare decays such as K+ —» ir+uv. New sources of CP violation can be discovered in kaon decays by measuring muon polarizations. The fascinating aspects of QCD and hadron physics will only receive brief treatment. This is partly due to my own ignorance and fortunately other speakers will cover this area more professionally than I will be able to.
The Standard Model
The standard model .of strong and electroweak interactions based on the gauge group SU(3)C x SU(2)i, x U(l) is remarkably successful. The basic build ing blocks are the spin - \ quarks and leptons. The quarks transforms as triplets under SU(3)C whereas the leptons are singlets. Under SU(2) the left-handed and right-handed quarks and leptons transform as doublets and singlets respectively. They are arranged in three families of ascending masses. There is no known rea son that this should be the case. However, it serves as a working hypothesis of family structure. Table I gives a list of the three quark and lepton families and their masses or limits as given in the Particle Data Group5. The only new infor mation is the limit mass of the t-quark, mt. A recent FNAL result gives mt > 60 GeV. The only other missing particle is the Higgs boson which is the only re maining physical particle after the SU(2) x U(l) symmetry is spontaneously broken by a doublet Higgs field.
- 9 - Table 1. Building blocks of the standard model and their properties. Values in the last column were obtained from the Particle Data Group (Ref. 6).
Spin Charge Color Mass GeV
0 0 < 2 x 10"8 1/2 Ci -1 0 0.51 x 10-3 2/3 3 5 x 10~3 (u) WL 1/3 3 8 x 10-3 h) 0 0 < 2.5 x 1004 U, 3 0 0.16 2/3 3 1.25 (c) -1/3 3 0.175 [s)L H 0 0 < 0.035 \rh -1 0 1.78
2/3 3 60 < mt < 200 (*\ W, -1/3 3 4.5
36 1 7 0 0 0< 3 x 10" w± ±1 0 80.9 ± 1.4 Z 0 0 91.9 ± 1.8 G 0 8 0
0 H 0 0 The standard model even with 3 families only contains a large number of arbitrary parameters. The three gauge groups each has their own coupling constant g„g and g' corresponding to SU(3), SU(2) and U(l) respectively. It is customary to trade g and g' into e, the electric charge, and 6w, the weak mixing angle. The relationship are (2.1) = tandw and e = ^sini9iw -10- Then there are six quark masses plus three charge lepton masses which are free parameters. Since the mass eigenstates of the quarks are in general not the weak eigenstates they are related by a 3 x 3 unitarity transformations. The 3x3 KM matrix contains 3 mixing angles and one CP violating phase. The scale of SU(2)£, x U(l) symmetry is also a free parameter. Using the Higgs mechanism this is represented by v the vacuum expectation value of the Higgs field. The W-boson mass is given in terms of v via Mw = -gv (2.2) The Higgs boson mass, Mg, is also a free parameter. Furthermore, the non- trivial structure of the QCD vacuum, gives rise to a P and T violating term, 0G"" G"" where C" is the gauge field tensor for SU(3)C and 5"" is its dual. Limit on the neutron electric dipole moment7,8 sets 0 < 10~9. This is a free parameter nonetheless. This adds up to 19 free parameters. If the neutrinos turn out to be massive, then we have 3 more masses plus 4 more mixing angles for the leptons. In spite of this unpleasantly long list of arbitrary parameters, the standard model has passed every experimental test thus far. The general structure of the charged and neutral currents coupling to the fermions are well established. There is only a few parameters of KM matrix yet to be determined. On the other hand the symmetry breaking mechanism remains a total mystery. Our only clue comes from the ratio of W to Z-bosons given by _JW£_ P 2 ~ M?cos Qw' Experimentally p ~ 0.998 ± 0.086 from fits of neutral current data. In the stan dard model, p = 1 is achieved by using doublet representation of Higgs only. This is independent of the number of Higgs doublets one uses. This in turn can be traced back to the existence of a custodial global9 SU(2) symmetry in the Higgs potential. The deep reason for this latter symmetry, if it exists, remains to be uncovered. On the other hand dynamical symmetry breaking schemes can also achieve p — 1 quite naturally. Unravelling the gauge symmetry break ing mechanism undoubtedly will be one of the most important tasks of particle physics. Without further ado we address some of the important phenomenolog- ical questions of the minimal standard model, i.e. with 3 families of quarks and leptons and massless or very light neutrinos. Hunting for the Higgs Boson Currently the only limit we have on the Higgs mass comes from arguments based on perturbative unitarity10 and hints that \ -11- on these it is commonly accepted that MH has to be lighter than i TeV. On the other hand there is no good theoretical lower limit on Ms- We have to rely on experiments. So far the only firm experimental limit comes from He4 decays. A search for 0+ particle emission in He4(20.1 MeV) decay has resulted in MJJ > 14 MeV. The preliminary data from the SINDRUM detector in their search of Higgs via T+ —* e+uuh° decays would seem to set MH > 110 MeV. If H° has a mass in the range .80 < MH < 1 GeV, KAON/JHP can play an important role in its search. There are two types of experiments to be considered. The first type are direct searches in reaction such as (3.1) TT+H° then follow by H° • fJ.+f*~. The latest result13 from BNL gives a branching ratio of B.R. (A'+ •K* H+li~) = 6.1 ± 4.0 x 10-8 and this is consistent with the standard model. Since the experiment reported only two candidate events, no firm conclusion of limit on the Higgs mass can be drawn. Furthermore, it is also hard to calculate the amplitude to K —> icH°. More theoretical and experimental works on these decays are certainly needed. The second type of search proceeds via virtual II0-exchange. An interesting and important experiment is the measurement of muon longitudinal polarization asymmetry, Pi, in the rare decay ii£ -* jifi (see Ref. 5). Pi is defined by NK-NL PL = (3.2) where NR(NI) is the number of right (left) - handed muons in the final state. Existence of Pi also violates CP invariance. This decay is GIM suppressed; hence it is sensitive to the unknown KM matrix element Vt, as well as the t-quark mass. Some typical Feynmann diagrams are depicted in Fig. (1). It is easily seen that d , d d S* I H° /* •--n~< W"| — -—< u,c, H° \jr Wc,t \ll (a) (b) (c) Fig. 1. Feynman diagrams for sd -» pji via Higgs boson exchange Pi varies as -gr. As an example a 10% measurement of Pi will be sensitive to MH ~ 1 GeV. Details of Pf, as a function of the KM phase S for MH = 1 GeV -12- and different mt is given in Fig. (2). One can see that a 10% measurement will be sensitive to the presence of 1 GeV Higgs if mt = 180 GeV. If one is lucky a light Higgs boson exists, then this decay is one of the few handles we have to probe the induced flavor changing vertex :sdH°. For a heavier H°, the search belongs mainly to the realms of colliders. For ma < 6 GeV, T —+ H°j decay is a favorite. However, there are uncertainties involving higher order QCD corrections14 and bound state effects that have to be considered. The soon to be operating e+e~ colliders SLC and LEPI will be sensitive to 10 < m# < 50 GeV using the following reaction e+e- _+ Z°'H° (3.3) I—• fi+fi~,e+e~, vv For raff between 50 and 100 GeV we have to await LEPII. The reactions in this case is associated Z°H° production and/or £+£~H°. For very heavy Higgs, i.e. 300 < mH < 1 TeV we have to rely on the SSC. We see from the above that the KAON/JHP will make a definite contribution in the search of H° if it is light, i.e. less than 5 GeV. In fact the discussion applies for any Higgs-like particles that exist in multiple Higgs models. Other models such as left-right symmetric model and supersymmetric extension of the standard model also have extended Higgs structure that can give rise to light Higgs particles. 14 a.-1 N O 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 8 Fig. 2. PL as a function of 6 in the standard model with Mg = 1 GeV. The curves labelled 1-4 are for mt = 60,90,120,180 GeV respectively. -13- The K-M Matrix and CP Violation The precision measurement of the elements of KM matrix and the eluci dation of the source of CP violation is one of the most important functions of KAON/JHP. Until a B-factory is built and operational, an intense hadron facility will corner this market. The charged weak current interaction Lagrangian of the quarks are given by C = —j-WpJ* + h.c. (4.1) with h = YJ ^LiVij-y^qjL (4.2) •'=M,« where Vij is the KM matrix. The current knowledge of the elements Vij is summarized in Table II. Table II Current knowledge of the values KM matrix elements. Vij Source If** |= 0.9744 ± 0.0010 0+ —* 0+ nuclear /?-decay VL, |= 0.220 ± 0.0020 iie3 and hyperon ^-decay | V |=0.207 ±0.024 cd CDHS v, V dimuon scattering data IK, |=0.95 ±0.14 IK, =0.043 ±0.08 b quark life time and semilepton b-decays | V* \< 0.012 2 2 2 Vti |< 0.024 Unitarity of KM | V^ | + | V* | + | Vtd [ = 1 Vta |< 0.054 Unitarity of KM matrix The task at hand is to verify the unitarity property of the KM matrix. Any departure from it will signify new physics such as the existence of a fourth generation. To do this one has to measure the elements of one row or column of the KM matrix precisely. The most precisely determined element is KJ and to improve it further will be very difficult. A further improvement in nuclear /3- decay runs into the theoretical ambiguities associated with radiative corrections to nuclear matrix elements. Pion /?-decay will be a way around this but the experimental difficulties are formidable. The element V,,, can certainly be better determined. A breakdown of the errors involved is shown to be | Vw |= 0.2196 ± 0.0014 ± 0.0018. The first -14- uncertainty is experimental and the second one is theoretical. It appears to me that both theoretical and experimental improvements can be made. We should aim at reducing both errors to ± 0.005; then a stringent test of unitarity can be achieved. This brings us to the element V^. Which can be measured directly by a search for charmless B-meson decays; i.e. decay modes where no explicit charm particles exist in the final states, e.g. B% —+ ppir. Currently, experimental discrepancy exists between CLEO which did not see this mode and ARGUS which claim to have seen them. We eagerly await the resolution of this issue. Vub can also manifest itself in second order weak effects; notably K° — K° and B° — B° mixing. In the minimal SM the recent measurement of B° — B° mixing implies a heavy t-quark and [ Vui, \£ 0. How can KAON/JHP help in determining these unknown KM elements? The favorite reaction is K+ —* ic+vv which proceeds through a second order weak interaction and fie GIM mechanism. The element Vtd and the related Vst enter due to a virtual t-quark exchange (see Fig. 3). The t-quark contribution is particularly important if it is massive e.g. mt > 80 GeV. For details see the beautiful talks by Drs. Lim and Bryman in this workshop. It is clearly seen that physics at KAON/JHP, B-mesons physics at e+e~ colliders, and t-quark search at hadron colliders are closely knitted together. Discovery of any one of them has a significant impact on others. I am confident that all three experiments will record positive results sometime in the future. This will have far reaching impact in particle physics. a) (u.c.t) (e,/i,T) b) s / (u,c,t) (u,c,t) Jv\AA/\A^ V d Fig. 3. A Feynman diagram for 2 -* d B v decay. The dashed lines denote W-boson exchanges. -15- Now I will turn to CP violation. The source of this very small effect is a total mystery. The strength is characterized by | e | ~ 2 x 10~3 i.e. a thousand times smaller than weak interaction. In the KM parameterization of the SM there is only one CP violating phase 6. The paradigm accommodates such a phase but does not explain where it comes from. The smallness of its strength is due to the very small mixing angle involved. Typically it goes like A5 in the kaon system where A = sin $c and 8e is the Cabibbo angle. For almost twenty years, experiments on CP violation effects have been mainly done on kaons where it was first discovered. Recently, positive mea surement of y = 3.3 ± 1.0 x 10-3 is reported15 in K -* mr decays which if confirmed will rule out superweak theories. This result lies within the predic tion of the standard model and will be the first confirmation of the effects of peuguin diagrams giving rise a non vanishing value of ^. A word of caution is appropriate here. The t-quark contribution to e* is non-negligible if mt > 100 GeV whereas e is relatively insensitive to mt. It is not clear that the standard model can accomodate the NA31 result with mt > 100 GeV. At KAON/JHP this measurement should be improved upon. This will fur ther elucidate the dynamics involved, our current understanding of this is very crude. Needless to say, if the CERN measurement is not confirmed, it will be of paramount importance to probe j at 10-4 level. One should keep close watch on the developments here. In the past year there has been a lot of attention given to the rare decay K° -• ^e+e- (3.3) as a test of CP violation in the SM model16. The importance of a further test of the KM paradigm is self evident. The branching ratio of (3.3) is estimated to be around 10_u ~ 10"12. The high flux at KAON/JHP will certainly be of help. Another experiment along this line is the decay K^ —* itQvv. However, the difficulties in measuring this cannot be under estimated. What about CP violation beyond the KM model? Here the field is wide open. Typically theorists construct models that gives rise to CP violation effects much larger than given by SM. A well known example is EDM of the neutron. There is no shortage of models that predict dn at the experimental limit. In the kaon arena the discussion focused on muon polarization. The first one of such experiments is the K^ —+ ftp. which I have previously discussed in terms of light Higgs bosons in the SM or extended Higgs model. Left-right symmetric model can also give a Pc in the range of a few percent. A second experiment is the transverse muon polarization in K^ decays17. This is principally a probe of charged Higgs boson as a source of CP violation.18 Many models of CP violation beyond SM also predicts EDM, de, for charged 19 leptons. In a class of model with extended Higgs one finds du/dt ~ \^gj ; hence d^ can be very large. With improved muon flux at KAON/JHP one -16- should be able to measure this either as a dedicated experiment or as a parasite to an improved g-2 experiment. sin2^ Measurement Now I return to the precision tests of the neutral current section of SM. The one fundamental parameter is sin2 &w which is the equivalent of a in QED. Hence it should be measured as accurately as possible. It is a touchstone of all grand unified models to be able to predict it correctly. To date there are more than 100 experiments measuring sin? 0w. Broadly they are classified as follow: (i) Deep inelastic u^ N scattering (ii) Mass measurement of Mw and Mg (iii) Vn e and vt e scattering (iv) e-D asymmetry in longitudinally polarized electron scattering (v) Atomic parity experiment in Bi, Th, Pb and Cs (vi) Elastic i/M P scattering (vii) Asymmetry measurements in e+e~ —• fi+/i~ at TRISTAN, SLC and LEP. Currently the world average of all measurements6 give sin2 Qw = 0.230 ± 0.0044. A further improvement we will have to rely on clean experiments where no or little uncertainty of hadron physics enters. This implies (ii), (iii) and (vii) will give the most relevant and unambiguous measurements of sin2 Qw With improved neutrino fluxes available we can aim at achieving 0.5% measurement at an IHF. This also means that new and more sophisticated detectors will be required. This does not mean the other types of measurement are not important. They are very invaluable in probing other kinds of physics. For example i/MP elastic scattering can be very use'ful for QCD in helping to pin down the strange quark content of the proton. Hadron Physics and QCD Quantum chromodynamics is emerging as the leading candidate theory of hadrons and their interactions. Strong hadronic force has its origin in the quarks interacting through the exchange of vector gluons. The most fundamental as pect is that the theory is a gauge theory with the gauge group SU(3). This is known as the color gauge group. The coupling constants of the interaction displays the phenomenon of asymptotic freedom. At higher energies and q2 the effective strength of interaction is smaller than at lower energies and q2. Hence, perturbation theory is expected to hold at high energies, e.g. above 100 GeV. -17- At lower energies perturbation theory breaks down. The color degree of freedom is also confined. In QCD, the gluons have self interactions, that is to say 3 - and 4 glu- ons vertices exist. This is not the case for QED. Color confinement and the strong nature of the coupling constant at low energies lead to the existence of pure gluonic resonances or glueball states. The existence of these objects were demonstrated in lattice gauge calculations20. Some experiments have laid claims to spotting them.21 Searching for these glueball states will be very important at an intense hadron facility. A typical example will be a reaction such as jr~p —y tj> looking for a resonant Fig. 4. Partou model diagrams from OZI - violating rection vp -* Conclusions I have given a sampling of the particle physics at KAON/JHP. In the elec- troweak sector the emphasis is unabashedly slanted toward the standard model. This is a reflection of the success the model currently enjoys. As theorists we can make confident predictions with the model. Beyond SM we can only make guesses and estimates. At an intense hadron facility, with the availability of intense kaon and neu trino beams, we can test SM as we have never been able to do before. New physics can be discovered if experiments fall outside the predicted values or -18- ranges. An example is K+ —* p.+vu where SM gives its branching ratio to he between 1 x 10~10 and 8 x 10~10. If we are lucky enough to find a disagreement with SM here then much further experimentation will be needed to unravel the origin of the new physics. Obviously, KAON/JHP will be an invaluable facility. Searching for new physics via SM forbidden decays is very important and we should not neglect them. Some well known examples are K\ -* pe, K+ —» ir+ne and K+ —• n+ 77 and ir hh where 7 and h are the photino and higgsino of supersymmetric theories. Lest we forget, the rare decays /*+ —* e+j and eee have played an important role in constraining model building such as horizontal symmetry models, supersymmetric models, and the class of models with heavy neutrinos. These rare muon decays can be much improved at KAON/JHP. The importance of these searches cannot be over emphasized as they touch upon one of the deepest puzzle of SM - the family problem. New experiments on CP violations will certainly be important at KAON/JHP. Here the discussions have only just begun. Neutrino oscillations is a common theme for many GUT or superstring in spired models. The difference of neutrino masses squared can be probed to 10-3 eV2 level at KAON. Perhaps with more clever ideas we can go even further. In the QCD arena, KAON/JHP will help in unravelling the mysteries of the dynamics in the confinement region. The spin content of the proton can be probed using neutrinos and polarized proton beams. This strikes at the heart of the most fundamental hadron which the universe and all of us are made out of - the proton. Is the proton just three valence quarks? References 1. M. Kobayashi and T. Maskawa, Prog. Theor. Phys. 49 652 (1973). 2. For a review on weak decays, see G. Belanger, et al., Proceedings of Snow- mass Summer Study of High Energy Physics in 1990's, (to be published). 3. For a review see A. Buras, Proc. of Rare decays Symposium, Vancouver, 1988, Edited by D. Bryman, J.N. Ng, T. Numao and J-M. Poutissou (to be published, World Scientific 1989). 4. S. Raby, J. West and C.W. Hoflmann, Phys. Rev. D_39 828, (1989). 5. F.J. Bottola and C.S. Lim, Phys. Rev. Lett 56, 1651 (1986). C.Q. Geng and J.N. Ng, Phys Rev. D, (to be published, 1989). 6. Particle Data Group, Phys. Lett. 204 B, 1 (1988). 7. I.S. Altarev et d., JETP Lett. 47, 460 (1980). -19- 8. For a review see S. Barr and W. Marciano, CP Violation, Ed. C. Jarlskog, (World Scientific, 1989). X. He, B.H.J. McKellar and S. Pakvasa, Univ. of Hawaii, preprint UH- 511-666-89 (1989). 9. P. Sikivie, L. Susskind, M. Voloshin and V. Zakharov, Nucl. Phys B 173, 189 (1980). 10. B.W. Lee, C. Quigg and H.B. Thacker, Phys. Rev. Lett., 38, 883 (1977) Phys. Rev. D 16, 1519 (1979). 11. M. Aizenmann, Phys. Rev. Lett., 47,1 (1981) J. Frohlich, Nucl. Phys., B 200, 281 (1982). 12. S. Egli et al., PSI preprint 89-02, (1989). 13. M.A. Selen, Princeton Univ. thesis (1989). 14. M.F. Vysotsky, Phys. Lett 97B, 159 (1980). P. Nason, Hid., B 175, 233 (1986). 15. For a status report see H. Wahl, Proc. of Rare Decay Symposium, Vancou ver, 1988, edited by D. Bryman, J.N. Ng, T. Numao and J-M Poutissou. (to be published, World Scientific, 1989). 16. J.M. Flynn and L. Randall, U.C. Burkeley report, UCB-PTH-88-29. CO. Dib, I. Dunientz, F.J. Gilman, SLAC-PUB-4762, (1988). L.M. Sehgal, Aachen preprint (1988). 17. M.K. Campbell et al., Phys. Rev. Lett. 47, 1032 (1981). 18. A.R. Zhitnitskii, Sov. J. Nucl. Phys. 6, 598 (1980). M. Leurer, Phys. Rev. Lett., 62,1967 (1989). 19. C.Q. Geng and J.N. Ng, TRIUMF preprint (1989). C.Q. Geng and J.N. Ng, Phys. Lett., B211, 111 (1988). 20. See for example, B. Berg, DESY preprint 84-012, (1984). 21. S.J. Lindenbaum and R.S. Longacre, Phys. Lett 165B, 202 (1985). -20- PARTICLE PHYSICS PROSPECTS FOR THE KAON FACTORY Douglas Bryman TRIUMF, 4004 Wesbrook Mall, Vancouver, B.C., Canada V6T 2A3 ABSTRACT The Kaon Factory at TRIUMF will produce beams of kaons, antiprotons, neutrinos and other particles with a hundred-fold increase in intensity over existing machines in the 30 GeV region. This will make possible new high precision experiments designed to test current ideas as well as high sensitivity measurements which could potentially reveal new effects. A sample of particle physics experiments involving rare kaon decays, CP and T violation studies, neutrino properties and reactions and light quark spectroscopy which might take advantage of the new opportunities presented by the Kaon Factory is discussed. I. INTRODUCTION The prospects for particle physics experiments at the Kaon Factory are varied and the emphasis will be on attacking many of the same issues addressed at the energy frontier of the high energy colliders. The experiments to be done at the 30 GeV, 100 /iA proton synchrotron proposed at TRIUMF will make use of the increase in current over existing machines in this energy range to achieve high precision or high sensitivity to carefully probe predictions of the standard model and to search for new effects. Unprecedented fluxes of kaons, antiprotons, hyperons, neutrinos, pions and muons will all be available to open up new possibilities for experimentation. Some particular areas of interest at the kaon factory include rare kaon decays, CP and T violation, neutrino properties and reactions and hadron spectroscopy. In the following, a few examples of the physics opportunities generated by the advent of the kaon factory will be discussed. II. RARE DECAYS AND CP VIOLATION Rare decays of mesons and leptons play a significant role in challenging the standard model and in searching for effects which could indicate new directions. Kaon decays have been a rich and often surprising source of information at every stage in the development of the present picture of fundamental particles and their interactions. Parity violation, CP violation, neutral currents and the existence of charm are all effects in which kaon decays exhibited crucial or unique features. Kaon decays remain in the forefront of modern high precision attempts to test the accuracy of standard model predictions, to define the nature of CP violation, and to search for neutral flavor changing currents and lepton number violation among other new interactions and particles. For recent reviews of rare kaon decays see Ref. 1 and 2. A. K+ -* it+vu Reactions which are allowed in the standard model can provide important, detailed information, and can also herald the presence of new effects. The process K+ —* t^vv offers a prime example of the unique opportunities available in the study of rare kaon -21- a) b) c) Fig. Second order weak diagrams for K+ — TC+VV. decays because a reliable higher order calculation assuming three generations can be confronted by experiment. Non-conformity with the standard model prediction could imply new physics in the form of extra generations or entirely new types of particles or interactions. The rate for K+ —• ir+i/v depends on parameters of the Cabbibo- Kobayashi-Maskawa (CKM) matrix as evidenced by the diagrams in Fig. 1. Constraints on the CKM mixing parameters Vt'3Vtd have been derived from semileptonic 5-meson decays, from the measured 6-quark lifetime and from the large observed _B° — _B° mixing which, for example, fixes Vtd (although with considerable uncertainty at present). The K+ —• t*vv branching ratio as a function of the i-quark mass with the dependence -1 on uncertainties of 5-meson decay observables lies in the region 1 to 7 x 10 ° for mt in the range 50 to 200 GeV/c2.2 Ellis and Hagelin3 calculated radiative QCD effects indicating that if the mixing angles and t-quark mass were known a firm prediction for the K+ —• v+i/0 branching ratio could be made. Conversely, a measurement of the branching ratio would be significant in constraining these parameters and would allow a direct test of higher order weak corrections in the standard model which is not significantly constrained by uncertain long distance effects as in calculations of K^ —• fifi and the •£"£ - K^ mass difference. A precise standard model prediction for the K+ —• x+vv branching ratio allows the reaction to be used to search for new physics. The least exotic addition to the present picture would involve additional generations of quarks and leptons. Since experiments measuring K+ -* T&VV do not observe the weakly interacting decay products, it is possible that this reaction is accompanied by K+ -+ ir+xx' or Jt"+ -> x+z, which occur at comparable or even much higher rates. The window for exotic effects appearing -22- Y VETO PHOTOTUBES :/• -U=U | RANGE STACK I PHOTOTUBES \MWPC CHAMBERS*. SPOKE \ IUNGE STACK /Ji "L' ' "' REGION VSCINTILLATOR jr_ END Fig. 2. Apparatus for BNL-787 measurement of A'+ -» TT+W. in the reaction K+ —• ir+xx' extends two orders of magnitude from the current limit B(K+ -* ir+xx') < 1.4x 10-7,4 to the upper level of the standard model value B{K+ -* TT+VV) ~ 10-9. In supersymmetric theories a variety of new particles are hypothesized including the supersymmetric partners of the photon (7), the Higgs particle (J?), the leptons and the quarks. These could contribute to the rate for K+ -* K+XX', if the masses are sufficiently small. Schrock5 estimated that if tree level graphs dominate in the decay K+ -* r+ 77, then the branching ratio could be as large as 10-7, near the current limit. Other possibilities for exotic reactions I(+ —* ir+xx' and K+ —• ir+x involving scalar or pseudoscalar particles have been suggested. The Majoran (a massless Nambu- Goldstone boson), the axion, light Higgs particles, the familion and hyperphotons are all potential candidates for x above. An experiment is now in progress at Brookhaven National Laboratory (BNL) to measure the process K+ —• ir+vv.6 The apparatus for BNL 787, a BNL-Princeton- TRITJMF collaboration, pictured in Fig. 2t is a state of-the-art detector which builds upon earlier work (such as Ref. 4) and points the way to future efforts at the kaon factory. The 787 detector has a large geometrical acceptance (2T sr) for the K+ -* T+VV decay mode and has been designed to maximize the rejection of background processes such + + + + + + as K -+ 7r ff° (K„2), K —* /* "r (K 112)1 K -* /* "7, and others. Sensitivity for identification of unaccompanied pions from K+ —* ir+vv is accomplished through measurements of momentum, kinetic energy, range, decay sequence x -> /i -» e, and nearly 4ff coverage for detection of photons. The 800 MeV/c K+ beam is brought to rest in a 10 cm diameter target consisting of groupings of scintillating fibers 2 mm in diameter viewed by photomultiplier tubes. The decay pions pass through a cylindrical drift chamber which measures their momenta in a 1 T magnetic field. The pions then stop in a plastic scintillator range stack which also contains multiwire proportional chambers. Each range stack counter is viewed from both ends by 5 cm phototubes read out by 500 MHz transient digitizers, so that the decay chain y. —* p —* e can be observed for particle identification. The total energy of the decay pions is measured by summing the pulse heights of the target and range array elements. The pion detector is completely surrounded by a IS radiation length Pb-scintillator gamma veto (1 mm Pb, 5 mm scintillator). Figure 3a shows an example of a calibration event of the type K+ —• 7r+jr°. A blow-up of the segmented target is shown in Fig. 3b. Energy and time for each target element are available at present from an ADC and a TDC, respectively, so that the incident kaon and outgoing pion elements can be identified. The momentum calculated from the track in the drift chamber is 198 MeV/c, determined with resolution ffp = 2.5%. The pion track energy is found by summing the range stack and target energies to be 97 MeV with a resolution of -24- 5© 0 (a) 60 RUN 2978 EVENT 79 50 SECTORS 17-20 LAYER 12 40 UPSTRERH 30 20 10 (c) -5300 -5250 "5200 -5150 "5100 Fig. 3. A'+ — JT+7T0 event in the BNL-787 detector (see text). The 787 experiment had a preliminary run in 1988. Present indications are that the experiment may be limited by the available flux of kaons rather than by background processes for the region of phase space (above the K*2 peak) being examined. If the standard model prediction is valid then at most a few events from K+ —* irvv can be expected. To examine the spectrum for consistency with the standard model, to investigate any new phenomena which might eventually turn up or to continue the search for this unique process will require the intensity available at the kaon factory. A conceptual design for a kaon factory detector for K+ -* i:+vv capable of operat ing in a flux of one to two orders of magnitude greater than presently available is shown in Fig. 4. The basic configuration is similar to that of 787, although the magnetic field strength is 3 T, three times stronger. The primary motivations for the high field are -25- IRON RETURN TORE Fig. 4. Conceptual design of a kaon factory experiment to measure K+ — ir+i/i/. improvement of the momentum resolution, improvement of the pion range stack track ing using greater segmentation (e.g. scintillation fibers) and improvement of the photon veto efficiency by the use of a fully active detection medium such as BaF2- The later two improvements are possible due to the reduced size of the high field tracking appara tus. To handle the high rates anticipated, all detector channels would be instrumented with 0.5-1.0 GHz transient digitizers like the ones used in 7877 and the GaAs CCD's under development at TBIUMF. A sensitivity of < 4 x 10-12 could be achieved with background levels estimated to be < 1 event. Alternatively, if the branching ratio is 5 x 10~10, 200 to 300 events would be observed. B. CP and T violation CP violation has only been observed in the neutral kaon system in K^ -* 2JT decays and in the charge asymmetry in K°L -* tte^v (Kf3) decays. In the standard model with at least three generations a CP-violating phase can be accommodated in the quark-mixing matrix. The magnitude of CP violation is indicated by the parameter e~10~3, which has as its source the K°, K° mass matrix. CP violation is manifested by the level of CP impurity of K% and K% states. A second possible source of CP violation originates directly from the K -* 2JT decay amplitude and is represented by the parameter e7. A recent CERN experiment8 (NA31) reported consistency with the CKM picture of -26- CP violation, finding a non-zero value (at the three-standard deviation level) for the ratio e'/e = (3.3 ± 1.1) X 10-3. Fermilab experiment E7319 which collected over 300K K% -* 2w° decays is expected to report a result for e'/e later this year with comparable or greater precision. Whether a non-zero value of e'/e is confirmed or (especially) if an inconsistency appears future higher precision experiments with perhaps 108 Ji'£ —*• 27r° events will be required for the next generation of experiments studying the origin of CP violation. This would allow the statistical precision to approach the 10-4 level, representing an order of magnitude improvement and presenting a severe challenge to the standard model. Of course, knowledge of systematic uncertainties must also be improved commensurately. Hence, the kaon factory has a definite role to play by permitting the creation of extremely clean beams (e.g. by charge exchange) while maintaining sufficient intensity or, perhaps, by employing entirely new techniques. New experiments at- an upgraded Fermilab booster have also been suggested.10 One promising approach to the CP violation problem that may merit kaon factory intensities for future work is the production of pure, tagged A'0 and A'0 states in pp annihilation. This method which is being pursued for the first time at LEAR,11 em ploys the reactions pp —* K°K~~+ and pp —>• K°K+-ir~ (branching ratios ~ 10~3) in + + which the K°{K0) state is tagged by K~x (K ir~). Time dependent CP violating asymmetries 0 A m = r(A-°--/xo-r(A- ->/)(t) A; r(A'°^/)(o + r(A-°^/)(*)' where / represents a final state such as ff°5r°, can be measured with estimated precision comparable to the current round of tests at CERN and Fermilab. These measurements of e'/e as well as the associated phases and other CP violating A's and KL decay modes will be done with quite a different set of systematic uncertainties than in the CERN and Fermilab experiments and, thereby, will represent an important consistency check. A further use of antiprotons in the quest for information on CP (or T) violation may come to fruition at the kaon factory by studying asymmetries of hyperon polarizations in reactions such as pp —• AA and pp —* 5+5~ as discussed by Hamann.12 Such reactions could provide a clean way to study CP violation outside the neutral kaon system since large hyperon polarizations (required by parity conservation to be transverse to the production plane) occur in the context of initial and final states with definite CP prop erties. Non-zero measurement of one of several possible observables would constitute definite evidence for AS = 1 CP violation (since due to baryon number conservation there is no final state mixing). Predictions for the CP violating asymmetries are at the 10-4 level while current experiments on pp —* AA13 and J/ip —* AA14 are in the neighborhood of 10-2 and new experiments at LEAR may obtain an additional factor of ten in sensitivity (see Ref. 12). To confront the standard model predictions one or two orders-of-magnitude more intensity will be necessary. Studies of cascade produc tion pp —• E+E~ which are particularly attractive due to self-analyzing decay modes E —• AT (up-down asymmetry measured) and A —• pit (A polarization measured) can occur with intense higher energy p beams at T/S > 2.64 GeV/c. Additional sources of CP or T violation could be revealed in rare kaon decay pro cesses involving measurements of the transverse nraon polarization in K —• irfiv (AVO decays not expected in the standard model. The presence of nonzero muon polarization -27- transverseto the decay plane is an indicator of T violation due to the T-odd product the two form factors /+(PK + Pv) and /-(PK - •?*), since T-invariance requires /+ and /_ to be relatively real. The results derived from measurement of the transverse /i polarization can be expressed in terms of Imf, where Im£ _ NL-NR 3 -28- where NL (NR) is the number of left- (right-) handed muons. However, much larger values can occur in Higgs models of CP violation. Here is an excellent example of a process which can be used to search for new effects such as alternate sources of CP violation while ultimately attempting to confront the standard model prediction. No experiments have yet been done and it appears that the intense beams at a kaon factory would be required to reach the 10~3 level. C. Lepton flavor violation Searches for rare kaon decays not expected in the standard model could also con tribute dramatic new information. Lepton flavor violating (LFV) interactions are strictly absent in the standard model with massless neutrinos because neither the intermediate vector bosons nor the Higgs particle have LFV couplings. However, in many exten sions of the standard model LFV interactions appear naturally, leadir to decays like A"2 -* y.e and K+ —• jr+/xe. Among these are models in which flavor violations are mediated by horizontal gauge bosons, additional neutral Higgs particles, vector or pseu- doscalar leptoquarks and supersymmetric particles. The mass regions probed by rare kaon processes reach scales of order 100 TeV/c2, which are inaccessible to direct experi ments at any existing or planned higher energy accelerator. Table I (fom Ref. 1) gives a sample of the mass regions probed by current experiments. Thus, although kaon decay experiments are generally performed at relatively low energies, their implications are relevant and complementary to studies done at the highest energy facilities. The ideas of quark and lepton substructure are motivated by the proliferation of fundamental particles and the lack of understanding provided by present theories. The existence of common substructure entities could conceivably lead to intergenerational rearrangement processes in which quarks and leptons are interchanged. Examples of reactions in which the net change of generation number is zero are K% —• fie, K+ —• + + + + H ve, and A' —» ir n e~. In some models these processes are mediated by exchange of heavy bosons which distinguish the generations. Other allowed rare kaon processes that might be accessible at the kaon factory could enable searches for exotic effects or new particles. The decays K —» ve+e~ and K —> ir/x+/i~, involving both neutral and charged mesons, can be used to search for light scalar particles, e.g. Higgs particles which decay via H —- l+l~. Several experiments have been performed to search for heavy neutrinos in M —• lu decays, where M = it or K and / = p or e. Heavy neutrinos V{ are not prohibited by any model (although there are some cosmological and other indirect constraints on masses and lifetimes) and could be mixed with the dominantly coupled light neutrinos if the weak eigenstates "e. " vT ... are distinct from the mass eigenstates. Other rare kaon decays, such as Ji'£ -» 77 and K% -* 77, are of interest due to the unknown aspects of low energy QCD and as additional sources of information on CP violation. Long distance (i.e., mesonic) effects generally contribute significantly to the uncertainties of calculations of such processes. The present round of rare decay experiments at BNL and KEK has already begun to produce significant new results as indicated in Table I." Because of the leverage that these experiments have in probing the standard model as well as in searching for new effects it can be expected that additional work taking advantage of new technology will "See also the contribution of Inagaki to these proceedings. -29- Table I. Mass bounds from different processes. Higgs Pseudoscalar Vector Experimental Process scalars leptoquarks leptoquarks value (GeV/c2) (TeV/c2) (TeV/c2) 10 a r(A'i-aU) 11 8 149 <3 x 10- 4.7 3.6 62 9 x 10~9 b 8 2.6 108 <1.2 x lO-9 c 1 0.5 5.6 <1.8 x 10-9 d r(u~e-,) _u e r(w-aU) 0.3 - - <4.9 x 10 T(w—*eee) 2.6 - - <1.0 x 10~12 f 22 22 118 <4.6 x 10~12 8 Am(ii:°-A'°) 150 - - 3.5 x 10-1S GeV b aW.R. Molzon, Proc. Rare Decay Symposium, Vancouver (1988). bParticle data group, Phys. Lett. 170B, 1 (1986). CE. Jastrzembski et al., Phys. Rev. Lett. 20, 2300 (1988). dM. Zeller, Proc. Rare Decay Symposium, Vancouver (1988). eR.D. Bolton el al., Phys. Rev. Lett. 56, 2461 (1986). fU. Bellgardt, Nucl. Phys. B299, 1 (1987). «S. Ahmad et al., Phys. Rev. D38, 2102 (1988). be pursued at these facilities and that further improvements will be realized at the kaon factory. To chose an example, AGS experiment 79123 is now aimed at a sensitivity of approximately < 10-u for K^ -*• fte decay. If the final result is null, then a strong motivation exists, as it does now, for pursuing this reaction since it is one of the most favored in models which extend the boundaries of the standard model. A positive result would create a whole industry of experiments to explore the new effect. It appears that with evolutionary improvements to the beam, chamber systems and triggering and data acquisition systems that a level of sensitivity of < 10-13 could be achieved at the kaon factory using beams of one to two orders of magnitude higher intensity than are presently available. More drastic revisions to the approach such as attempting to increase the acceptance by an order of magnitude are worthy of consideration as well. Here, experience at the meson factories is relevant. The two orders of magnitude in flux compared with "pre-factory" machines coupled with advances in technology have already led to five orders of magnitude improvements in sensitivity of rare muon decay experiments with major advances still underway. -30- m. NEUTRINO PHYSICS High intensity neutrino beams with 100 times the flux presently available at the BNL AGS will also open many opportunities for fundamental studies including neutrino- electron and neutrino-proton reactions and searches for neutrino oscillations. Determin 2 ing sin 9W at low Q may be an important objective of neutrino physics experiments at the kaon factory. A high precision low Q2 measurement will enable tests of the calcula tions of radiative corrections which are required in order to connect low Q2 and high Q2 (~ M\) measurements. However, currently proposed experiments e.g. LCD at Lampf24 2 -3 may succeed in reaching precision sin 9W ~ 10 comparable to that attainable at the kaon factory so the situation will require reevaluation at a later date. Neutrino beams potentially available at the kaon factory include v^ from pion decay, medium energy ± T electron neutrinos from iif£ -• ff e ve decays-in-flight and low energy ve, i/^ and v^ from a beam-stop source. Neutrino mass and oscillation are currently active topics and can be expected to remain so through the kaon factory era. To explain the observed scarcity of solar neutrinos, a theory of matter oscillation has been proposed. If this approach were 2 -7 -4 2 correct and vs —• vM oscillations occur with Am ~ 10 — 10 eV , then vacuum oscillations v^ «-* i/e would be virtually out of reach in terrestrial experiments. However, 2 under various assumptions i>M «-+ vr oscillations might be accessible in the range Am ~ -4 4 2 2 2 10 -10 eV . Presently, Am ~ 0.3 eV have been searched for in v„. <-»• vr oscillations. A new proposal25 for the AGS with the booster under construction at BNL is aiming at an order of magnitude improvement in a v^ disappearance experiment with a 10 km baseline (corresponding to L/E ~ 10 where E is the energy (GeV) and L (km) is the observation-sonrce distance). 2 x 1020 protons on target are requested for this purpose. At the kaon factory :t is possible to consider the next generating experiment with 100 km baseline. This wonld enable examination of the vacuum oscillation region with large 2 3 mixing at the level Am ~ 10~ . New regions of oscillation parameters for v^ «•+ i/e could also be explored through vc appearance experiments. Neutrino experiments of this scale, clearly mL-jor undertakings, would be done in the context of then-current results of terrestrial and solsr neutrino experiments. IV. LIGHT QUARK SPECTROSCOPY Although in the above we have mainly dealt with electro-weak issues, strong inter action physics will also play a major role in the kaon factory program. For example, hadron spectroscopy is an area which still requires much effort in order to provide basic empirical information on the rich array of states expected in QCD inspired models. Fig ure 5 from Godfrey and Isgur shows a quark-antiquark potential for meson spectroscopy. Light quark states probe the non-perturbative QCD region whereas heavy quark pro duction, W and Z production and jet physics studied at high energy colliders probes the perturbative regime. In light baryon and meson spectroscopy there are many states expected in the quark model which have not been observed. Many inconclusive searches have also been performed for states composed purely of glue and for quark-glue hybrid states. Similarly, the whereabouts of multiquark states such as qqqqq and baryonium remain a mystery. A well-founded knowledge of spectroscopy of quarks and gluons will -31- iniij! nt '«* Fig. 5. The universal quark-antiquark QCD potential used by Godfrey and Isgur in their model of meson spectroscopy. be complementary to high energy perturbative QCD studies, and both will be necessary to obtain a thorough understanding of the strong interaction. This will be essential to eventually confront theoretical approaches such as lattice gauge theories which may one day provide predictive power along with a quantitative picture of QCD. Experiments at the kaon factory may include studies of light quark spectroscopy using it~p, K~p and pp interactions. Because high statistics and high resolution will generally be necessary to sort out the complex spectrum of states, these experiments will require advanced detectors with fast triggers, high rate capabilities and the ability to process enormous data sets. V. CONCLUSION The kaon factory will provide a new capability for high precision, high sensitivity particle physics experiments that is unique and complementary to many current and proposed efforts. The sampler of inviting possibilities discussed above is by no means meant to be complete or even representative of the program at the kaon kaon factory which will be driven by future physics issues and priorities. What is more certain is that as new intense beams with hundred-fold higher fluxes become available, they will be used in imaginative and productive ways to significantly aid in the advancement of physics. REFERENCES 1. D.A. Bryman, Int. Jour. Mod. Phys. A 4, 79 (1989). 2. L.S. Littenberg and J.S. Hagelin, to be published. 3. J. Ellis and J.S. Hagelin, Nucl. Phys. B217,189 (1983) 4. Y. Asano et a/., Phys. Lett. 107B, 159 1981- -32- The status of E137 at KEK An experiment to search for 1L •*• ue and ee T. Inagaki National Laboratory for High Energy Physics, KEK Oho, Tsukuba, Ibaraki, 305 Japan The rare K decay experiment, E137, to search for IL + jie and ee is being carried out at KEK 12 GeV proton synchrotron. The present single event sensitivity is 1.6 x 10 for both decays. The future prospect of the experiment is also discussed. Introduction This is a report from the E137 collaboration whose members are: T. Inagaki, M. Kobayashi, T. Sato, T. Shinkawa, F. Suekane, K. Takamatsu and Y. Yoshimura, KEK; K. Ishikawa, T. Kishida, T.K. Komatsubara, M. Kuze, F. Sal, J. Toyoura and S.S. Yamamoto, University of Tokyo; Y. Hemmi, Kyoto University. The K_ -•- ue is a separate lepton number violating process and is highly suppressed in the Standard Model. In the minimal extension of the Standard Model a branching ratio of ¥L -*• ue is calculated to be -17 1) around 10 by assuming the lepton mixing and the v mass presently allowed. The K_ + ee is expected to occur in a finite value by the Standard Model but it is highly suppressed by the GIM mechanism and by the helicity suppression. The predicted branching ratio is 5 * -12 2) 10 . Therefore, the observation of these decays in the present experiment of around 10~ sensitivity directly indicates the new physics beyond the Standard Model. -33- If there is a horizontal gauge boson (H„), K, + ue proceeds through a tree level diagram as shown in Fig. 1(a). With comparing to K + M v mediated with the weak boson (W) as shown in Fig. 1(b), the mass of the H boson being searched is about 30 TeV in a 10~ sensitivity. It cannot be directly searched even by the SSC. The K •+ ye has a unique character among various processes of the lepton number violation. The generation number is conserved in SL •*• ue, while it is changed in the rare muon decays some of which have been done at Triutaf. Experimental Apparatus Figure 2 shows an experimental setup of E137. In the upstream beyond the figure there is a 10 m beam line followed by a 10 m decay region. The detector is a two-arm spectrometer in the center of which a vacuum beam duct passes. The upstream part of each arm is composed of five drift chambers and two magnets. The material in this part, a vacuum window, drift chambers and helium bags, is minimized to decrease the coulomb multiple scattering. In the downstream part there are two trigger hodoscopes, a threshold gas Cherenkov counter and a lead scintillator sandwich counter for electron identification and four layers of counters sandwiched with ion blocks for muon identification. In the experimental point of view, IL •*• ue and ee are simple processes. Though the momentum of an incident BL is not defined directly, the momenta of decayed muon and electron can be precisely measured by the magnetic spectrometer. Two kinematical variables, an effective mass of two decayed particles and a colinear angle (8) defined as an angle between the target-to-vertex direction and the vector sum of the two particle momenta, are used to identify a signal. In any case the momenta must be measured with extremely high accuracy to discriminate a signal from background. As well known, the momentum resolution measured by the magnetic spectrometer is proportional to the momentum itself. The lower momentum beam guarantees the better resolution. This is an essential reason why we do this kind of experiment at KEK 12 GeV proton synchrotron which is comparatively poorer than other machines in the performance but which is the lowest energy machine to produce K's in the world. -34- Before showing our preliminary results, I'd like to pick following characteristic points of the experiment up. The first one is the fact that the process has good references, K. •*• ir ir~ and 1L. •*• HH decays. The IL + ir ir~ decay whose branching ratio is 2 * 10~ can be copiously detected and used for the monitor of the system resolution and for the normalization of number of IC's. The HL •*• w which is a GIM suppressed process of a 10 branching ratio has the same type of background from VL •* iryv as that from K_ •+ irev in the BL •*• ye search. The process is used to check the final event selection method. The geometrical acceptances of the detector for these processes are same in the first order approximation and the measurements are simultaneously done in the present experiment. The second point is characteristic of the background. More than 99% of Kr's decay into more than two bodies. Therefore the primary background will come from multibody decays and must be reduced at any levels. At a trigger level by adjusting the magnetic excitation so that the transverse momentum kick is equal to the maximum transverse momentum and by requiring parallelism after the magnet, the trigger acceptances for multibody decays can be reduced by about two orders of magnitude compared with those for two body decays. Most serious background for IC + (ie at an analysis level comes from K. + irev. If ir was mlsidentified as y by the pion punch-through, visible particles are u and e. As u is lighter than ir, the maximum lie mass is lighter than K^ mass (M„T ) by 12 MeV. If ir decays in flight through ir + yv, the visible particles are also y and e and the maximum ye mass reaches MIfT - 8 MeV because the decayed y is boosted in the forward direction. When ir decays in the magnet and emits y in the bending direction, the momentum will be mis-measured. In this case it is possible that the ye mass becomes to be equal to IL mass. However, this is a very rare case because we can check the track continuity in two dimensions and the colinear angle. It becomes serious in the experiment beyond a 10 sensitivity. The double stage configuration of magnets is selected in order to remove this contamination by reduplicated momentum measurements. Another serious background for the K. + y'y measurement is a double misidentification, ir to u and e to y of YL •*• irev. As Aye (= m - m ) is larger than Airy (= mff - m ). There is a chance that W mass happens to be KL mass. That is a main -35- reason why the electron identification is tight by the doubled identifiers of the gas Cherenkov counter and the shower counter. The last characteristic point is the fact that the experiment must be done in the high counting rate environment. The counting rate of the typical detectors in the present experiment is shown in Table. There are several extra hits in a upstream drift chamber plane and a few extra hits in a downstream drift chamber plane. By increasing beam intensity the data size per event increase as well as the trigger rate. It brings a serious problem in the data handling process. Another problem comes from a noise hit which coincides with a true hit. The noise hit destroys the true hit information and decreases the efficiency of track reconstruction. The limitation coming from these problems contradicts with the high flux requirement for the high sensitivity experiment. The optimization of the beam intensity to compromise between the high flux requirement and the limitation has been patiently done in the present experiment by changing the beam intensity with monitoring various effects. Preliminary Results and Discussions The followings are the preliminary results based on the data collected by Feb. 1989. Fig. 3(a) is a scattered plot of the TTTT mass 2 + - (M ) vs. 8 for the ir IT data. Events are well localized around M = HL, and 6 = 0. A histogram projected on M in the region of 8 < TO. c o 9 "^ 3 x io~° (radian) and a 6 distribution in the region 492 MeV < M < 502 MeV are shown in Fig. 3(b) and Fig. 3(c), respectively. From 2 —6 these figures a signal region was defined as 8 < 3 x 10 and 492 MeV < M < 502 MeV. In ue and ee data there are no events in the signal region as shown in Figs. 4(a) and 4(b). The single event sensitivity -10 + — was estimated to be 1.6 x 10 from the number of IL + ir ir events with assuming the branching ratio given by PDG. There are 54 events for uy data in the signal region as shown in Fig. 4(c). The branching _q ratio of JL + up is (8±1) * 10 which is consistent with the PDG value. The upper bound of the branching ratio for both K, •*• ue and K_ fte is 4 x 10~10 in 90% CL. The present best limits for these two decays are given by E780 at BNL to be 8.4 x 10~ and 8.9 * 10 , respectively. The preliminary result presented at Trimpf meeting by E791 ' at BNL is 3 x 10 for both decays. We expect to increase our data and get 100 uji's by this summer. -36- As discussed in the design report of the Xriumf Kaon Factory, the future experiment for this kind of decays must have a goal of 10 , which is higher than the present sensitivity by two orders of magnitude. The limit in the present experiment mainly comes from the high counting rate. The limit from the high counting rate appears not only in the tracking chamber but in all devices. Therefore we must polish up our experimental technique in various kinds of parts such as beam handling! electronics for fast logic and readout, data aquisition, etc. The resolution to discriminate a signal from background must be improved in the future experiment. Although we have already known the way to improve in some parts, two orders of magnitude looks very large. Therefore, I think that it is the best way to do a next step experiment at KEK whose sensitivity is 10 times higher than the present one before the future experiment at the Kaon Factory. In the next step we should collaborate with people from other countries, especially from Triumf. In the next step we could collaborate with the major energy frontier group such as the group for SSC, because they have the same problem of the high counting rate. References 1) A. Barroso, G.C. Branco and M.C. Bento, Phys. Lett. 134B, 123 (1984). 2) G.L. Kane and R.E. Shrock, Proc. of the Workshop on Intense Medium Energy Sourse of Strangeness, Santa Cruz, California, 1983. 3) S.F. Schaffner et al., Phys. Rev. D39, 990 (1989). 4) W.R. Molzon, Talk at Rare Decay Symposium at Vancouver, 1988. -37- Counting Rate NAME DEVICE Sensitive Area (count/pulse) upstream . _ Wl drift chamber 1 m 3 x 10 Trigger , , HI hodoscope 1.6 m 3 x 10 2nd counter „ , M2 in u-fitor 1.8 m 1.5 * 10 pulse: 500 msec, duration in 2.5 sec cycle. Table Counting rate at the operating point; 0° production from the 1.3 x lo1122 Z 3 from the 1.3 x 10 ppp beam, 10 x 120 mm cupper target and 150 ustr collimator. 38- (a) (b) Fig. 1 (a) Diagram for K, •*• lie mediated with a horizontal gauge boson, H . (b) Diagram for K -*• y\> through the weak boson, W. -39- MUON IDENTIFIER KL BEAM DECAY CHAMBER tVACUUM) HELIUM BAG HELIUM BAG MAGNET HI H2 SHOWER COUNTER SCALE >— 1m Fig. 2 Plan view of the experimental set up of E137. (a) J 4 01 460 490 500 910 M„ IMeV/c2! 4 S 8* Imrod2) Fig. 3 Preliminary results for IC •+• IT IT ; (a) scattered plot of irir 2 2 mass vs. 8 , (b) irir mass distribution in the region of 8 < 3 —ft 1 x 10~ and (c) 9 distribution for inr mass in the range 493-502 MeV. The signal region for K -»• TTTT, ue, ee and ee was defined from the (b) and (c) distributions, which covers the region of about three times of each resolution. -41- >"•!> • ' . ' ' "^ ' m-: : VA'" • '"• E 4 m-.---*:• •• . ,:•••••;•. B( *'•» l:\ .. i I I 500 510 z MMe (MeV/c ) • i E * - ,— r • i ' I • i > > I 500 M„ IMeV/c*) VtV-i;-.1. -• f • 1 1 1 (cl a ? ££-. • "It,". * 6 ~" • 1 t "'.• B « **"" I L * "* " : • ea ?;- • " . "f ff • 2 i •".££'.-1- eo 490 500 510 Kfn IMeV/c'l 2 2 Fig. 4 Scattered plots of (a) ue mass vs 6 , (b) ee mass vs 8 and 2 (c) uu mass vs 8 . These are the preliminary results based on the data collected up to Feb. 1989. -42- THE TRIUMF KAON FACTORY ACCELERATORS M.K. Craddock* TRIUMF, 4OO4 Wesbrook Mall, Vancouver, B.C. V6T 2A3 Abstract To accelerate a 100 y.k proton beam from the TRIUMF H~ cyclotron to 30 GeV a five-ring accelerator complex is proposed. Each accelerator is followed by a storage ring for time-matching - the cw cyclotron by the Accumulator, the 3 GeV 50 Hz Booster by the Collector, and the 30 GeV 10 Hz Driver by the Extender - the latter providing the slow-extracted beam for coincidence experiments. Under the current $11 million pre-construction study prototypes are being built of various components of the Booster ring - a fast-cycling dipole magnet, a dual-frequency magnet power supply, ceramic beam pipes, rf cavities (both parallel and perpendicular bias versions) and an extraction kicker. In addition the lattice designs for all five rings and the shielding and remote handling requirements are being reviewed. These activities will allow construction to start in 1990. Introduction The TRIUMF Kaon-Antiproton-Otherhadron-Neutrino Factory accelerators have been described in full in the original proposal1 and outlined in various papers.2-3 The basic aim is to accelerate a 100 (IPL beam of protons to 30 GeV, roughly 100 times more than available at present. The TRIUMF H~ cyclotron, which routinely delivers 150 /zA beams at 500 MeV, provides a ready-made and reliable injector. It would be followed by two fast-cycling synchrotrons, interleaved with 3 storage rings, as follows: A Accumulator: accumulates cw 450 MeV beam from the cyclotron over 20 ms periods B Booster: 50 Hz synchrotron; accelerates beam to 3 GeV; circumference 214 m C Collector: collects 5 Booster pulses and manipulates longitudinal emit tance D Driver: main 10 Hz synchrotron; accelerates beam to 30 GeV; circum ference 1072 m E Extender: 30 GeV stretcher ring for slow extraction for coincidence experiments The energy-time plot in Fig. 1 shows how this arrangement allows the B and D rings to run continuous acceleration cycles without flat bottoms or flat tops. The use of a Booster permits a smaller normalized emittance and hence reduces the aperture and cost of the Driver magnets for a given space charge tune shift. The use of a Booster also simplifies the rf design by separating the requirements for large frequency "On leave from Physics Department, University of British Columbia. -43- } 30 GeV 10 Hz '3 GeV 50 Hz } 440 MeV 23 MHz I i i i i i i i i i I i i i i i i i i i I i i i i i i—• Time (ms) 0 100 200 Fig. 1. Energy-time sequence for the five rings swing and high voltage (33% and 600 kV respectively for the Booster, and 3% and 2550 kV for the Driver). These high rf voltages are associated with the high cycling rates; the use of an asymmetric magnet cycle with a rise 3 times longer than the fall in the Driver (Fig. 1) reduces the voltage required by one-third, and the number of cavities in proportion. In the Booster the saving is less because more voltage is needed for bucket creation. Figure 2 gives a schematic layout of the lattices of the five rings, showing the arrangement of magnets, rf cavities and beam transfer lines. Although illustrated side by side for convenience, in practice the Accumulator would be mounted above the Booster in the small tunnel and the Collector and Extender rings below and above the Driver in the main tunnel. Identical lattices and tunes axe used for the rings in each tunnel. This is a natural choice providing structural simplicity, similar magnet apertures and straightforward matching for beam transfer. Separated-function magnet lattices are used with the dispersion modulated so as to drive its mean value towards zero, enabling transition to be kept above top energy in all rings. This avoias transition-crossing problems, such as emittance mismatch and change of rf phase under high beam loading. Racetrack lattices have now been adopted for the C,D and E rings and are under consideration for the A and B rings. Injection into the Accumulator is achieved by stripping the H~ beam from the cyclotron, enabling many turns to be injected into the same area of phase space. The small emittance beam from the injector is in fact "painted" over the much larger three-dimensional acceptance of the Accumulator to limit the space charge tune shift. -44- Fig. 2. Schematic layout of the lattices of the five rings Painting also enables the optimum density profile to be obtained and the number of passages through the stripping foil to be limited. Beam Dynamics In order to cut beam loss at slow extraction well below the usual 1%, racetrack lattices have now been adopted for the C,D and E rings (Servranckx et al.4). These provide long straights with high /? (100 m) at the septa and room for an additional pre- septum and for collimators downstream. Tracking simulations, which include power supply noise effects, show that the beam loss can be kept below 0-2%. The 180° arcs contain 24 cells, and are second-order achromats, normally tuned to 5 x 2ff. The tune for the whole ring may be varied by ±1 in each plane independently. A half-integer resonance may be used for extraction, to simplify the collimation process. Such a racetrack lattice is also convenient for the Driver synchrotron, allowing either for the insertion of Siberian snakes, or for tuning for low depolarization without snakes, using high-periodicity arcs and spin-transparent straight sections (Wienands5). In vestigation of the properties of the lattice in detail show that its dynamic aperture is as large as for the old circular design. A bypass is being studied for the Extender, to separate the extraction straight from those of the C and D rings. Racetrack lattices are also being investigated for the Booster and Accumulator rings, where they would -45- provide dispersion-free regions for rf cavities and beam transfer. FODO, doublet and triplet lattices are being investigated.4 Studies continue to determine the optimum strategy for painting the beam at injection. Developments in stripping foil construction suggest that two-sided "corner" foils may be usable, reducing the number of foil interceptions during accumulation (Mackenzie6). Better models axe now available for scattering within thin foils (Butler et al.7). The stability of unusual beam density distributions, such as those formed during painting or debunching, is under study (Baartman8). For distributions p(p, 0) hollow in longitudinal phase space, simulations9 reveal an intensity threshold for instability. The stability criterion can be expressed in terms of the slope dp/dp. The merits of lower-frequency rf systems for beam stability have also been studied.10 The effects of space charge and of feedback control loops can be included in our longitudinal tracking codes, and have also been studied analytically. Magnet Development A preliminary design for a Booster dipole magnet has been prepared (Otter et al.11) and a prototype is under construction. The magnet will be 3 m long with a pole gap of 10.7 cm and will cycle at 50 Hz between 0.27 T and 1.05 T with a field uniformity < ±2 x lO-4 over ±5 cm. The prototype will be built from 26-gauge laminations of M17 (non-grain oriented) steel with 10-turn coils, each containing 12 square hollow copper conductors in a vertical array. Studies continue on the various other magnets needed in the accelerators and beam lines. Fig. 3. High-power test stand for dual-frequency magnet ex citation studies. -46- Magnet Power Supplies As explained above, dual-frequency magnet excitation is being considered for the synchrotrons, with a rise time three times longer than the fall. To test the performance of such a system a high-power test stand has been set up (Fig. 3). Four magnets from the decommissioned NINA synchrotron are used, one as the load and three in series as the resonant 81 mH choke, A 1000 (tF capacitor bank may be switched in parallel with a 125 pF bank to change the resonant frequency from 100 Hz to 33 Hz. Dual- frequency operation was achieved recently and tests are continuing (Reiniger12). A new power distribution scheme for the one reference and 24 Booster dipoles has been worked out, based on 5 cells with 5 magnets each. This project has greatly benefitted from the participation of Prof. H. Sasaki. Kickers The kicker with the most challenging specifications is probably that for extraction from the Booster ring - about 30 kV across an 8 cm gap over a length of 2 m with a rise time <80 ns and operating at 50 Hz. Starting from scratch and with long delivery times on some items it seemed impractical to attempt to build a true prototype within 12 or 15 months. Instead we plan to gain experience in delay-line kicker technology by putting together a somewhat similar system with the help of some critical components obtained on loan from CERN. A 1 MHz chopper will also be built for installation in the injection line from the cyclotron to create the 110 ns beam gap needed for kicker rise and fall. The chopper must provide 40 kV over 1 m with rise and fall < 35 ns. Our aim is to have a prototype chopper operating by the end of 1989. Radio Frequency Systems The reference design for the Booster cavities is based on those used in the Fermilab booster. A full-scale prototype cavity is almost complete and should be ready for tests with an air tuner soon (Poirier et oZ.13). Under our collaboration with LAMPF their booster cavity, which employs perpendicularly-biased microwave ferrite, is now also at TRIUMF, being prepared for testing under ac bias conditions - a crucial test of its viability. Under dc bias it has produced relatively high voltages (140 kV), potentially reducing the number of cavities required and hence the impedance presented to the beam and the likelihood of inducing coupled-bunch instabilities. Enegren et a/.14 have studied the higher-order modes for both cavities and report on several damping schemes. To reduce the stray magnetic field seen by the beam in the LAMPF cavity, both shielding and redesign of the bias coils are being investigated (Haddock et al.is). The revised design is shown in Fig. 4. Control of the rf systems under high beam loading is a crucial topic. The effect of fast feedback has been modelled analytically by Koscielniak.16 Burge and Enegren17 -47- have described the operation of a generic regulator they have built for phase and amplitude control. This will be used in the low-level control system which TRIUMF is building for the LAMPF main ring cavity, along with the solid-state driver amplifier. x BIAS COIL Fig. 4. Los Alamos rf cavity with new foil arrangement for biasing the ferrite radially instead of axially. Beam Pipe Sc Vacuum The vacuum and impedance requirements for all five rings are being carefully reviewed (Oram18). The high circulating beam current makes beam-induced multi- pactoring and ion desorption from the walls the most critical processes. A hydro carbon-free system is required, with all metal elements pre-baked to 300°C, and pumps spaced no more than 5 m apart, automatically producing vacua better than 10~8 Torr. An additional concern in the Extender ring, where the beam may be debunched, is the possibility of electron-proton oscillations; electrostatic collector plates will be needed to suppress these. Ceramic chambers must be used within the fast-cycling magnets but must contain a conducting shield. Two shielding schemes are being considered and 4 m long pro totypes incorporating each are being constructed for the Booster dipoles. SAIC (San Diego) is building a chamber with longitudinal silver stripes painted on the inside walls, while RAL (U.K.) is building one incorporating a separate wire cage, as used in ISIS. Computer Control System A comprehensive review of both hardware and software options was earned out by Dawson et a/.19 in 1987, and recommended a segmented Ethernet communications — &R— backbone linking commercial workstations used as operator interfaces with micropro cessor based equipment controllers. A test platform is being assembled based on a VAX3200 workstation with a bridged Ethernet connexion to 2 VME crates. It will be tried out on selected cyclotron systems requiring beam control, such as the injection line or the new H~ extraction system. The possibiUty of incorporating expert systems techniques is also under study. H~ Extraction From the Cyclotron To extract H~ ions (instead of stripping them to protons as in normal operation) a conventional extraction system is being developed. With 18 kV on an rf deflector, which Fig. 5. Schematic layout of the electrostatic extraction sep tum for H~ ions, showing the stripping foil which protects the septum from irradiation. excites the i/r=3/2 resonance, and 50 kV on the electrostatic deflector 90% of the beam (66 fiA macropulses at 1% duty factor) has been transmitted through the latter (Laxdal et al.20). The other 10% is stripped by a narrow foil shadowing the septum and protecting it from irradiation (Fig. 5); the resulting protons may be dumped or steered into an experimental beam line. In recent tests the average beam current was successfully raised to 10 /iA. Design of the 4-segment magnetic channel which will steer the H" beam out of the cyclotron is now under way and one segment will be built and tested this year. Detailed design of the front end of the external beam line is also under way. -49- Conclusion A wide variety of activities is under way to finalize the design of the KAON Factory accelerators. Prototypes are being built of many components of the Booster synchrotron and a comprehensive.review of the whole design is to be completed by the end of 1989, ready for a start to construction in 1990. TRIUMF has already benefitted from Japanese assistance with beam dynamics studies and with the design of magnet power supplies. With work under way on similar projects in Japan (the JHP compressor/stretcher ring, acceleration of radioactive ions and upgrading the KEK PS) there seem to be excellent opportunities for two-way collaboration in the future, to the benefit of both countries. Acknowledgements It is a pleasure to acknowledge the efforts of all those who have worked to im prove the KAON Factory design recently (a partial list is given earlier in these proceedings21). The advice and help of H. Baumann, D. Fiander, J. Griffin, M. Harold, E. Jones, C.W. Planner, G.H. Rees, H. Sasaki, H.D. Schonauer, T. Suzuki, E.J.N. Wilson and of our collaborators at LAMPF has been especially appreciated. The author is also particularly grateful to Jana Thomson for the accuracy of the typing. References 1. KAON Factory Proposal, TRIUMF, September, 1985. 2. M.K. Craddock, R. Baartman et o/., IEEE Trans. Nucl. Sci. NS-32, 1707 (1985). 3. M.K. Craddock, Proc. Int. Workshop on Hadron Facility Technology, Santa Fe, February 1987, ed. H.A. Thiessen, Los Alamos Report LA-11130-C, pp 8-31 (1987). 4. R.V. Servranckx, U. Wienands, et al., "Racetrack Lattices for the TRIUMF KAON Factory", Proc. 1989 Particle Accelerator Conference, IEEE (in press). 5. U. Wienands, "Polarized Beams at the KAON Factory", Proc. AHF Accelerator Design Workshop, Los Alamos, February 1989 (in press). 6. G.H. Mackenzie, "TRIUMF Stripper Lifetime and Desirable Tests for the KAON Factory", ibid. 7. M. Butler, S. Koscielniak and G.H. Mackenzie, "A Tabulation of Coulomb Scattering Cross Sections etc.", Proc. 1989 Particle Accelerator Conference, IEEE (in press). -50- 8. R. Baartman "Coasting Beam Instability Theory Applied to Bunched Beams", Proc. AHF Accelerator Design Workshop, Los Alamos, February 1989 (in press). 9. R. Baartman, F. Jones, S. Koscielniak and G.H. Mackenzie, "Stability of Beams Hollow in Longitudinal Phase Space", Proc. 1989 Particle Accelerator Confer ence, IEEE (in press). 10. R. Baartman, "The Case for Low-frequency RF Systems," Proc. AHF Acceler ator Design Workshop, Los Alamos, February 1989 (in press). 11. A.J. Otter, C. Haddock and P. Reeve, "Prototype Magnet Designs and Loss Measurements for the Dual Frequency Booster Synchrotron etc." Proc. 1989 Particle Accelerator Conference, IEEE (in press). 12. K. Reiniger, "The Generation of a Reference Design for Booster Magnet Exci tation for TRIUMF KAON Factory", ibid. 13. R.L. Poirier, T.A. Enegren and C. Haddock, "Perpendicular-Biased Ferrite Tuned RF Cavity for the TRIUMF KAON Factory Booster Ring", ibid. 14. T.A. Enegren, R. Poirier et al., "Higher-order Mode Damping in KAON Factory RF Cavities", ibid. 15. C. Haddock, R.L. Poirier and T. Enegren, "Biasing of Ferrite Tuners," Proc. AHF Accelerator Design Workshop, Los Alamos, February 1989, ibid. 16. S. Koscielniak, "System Stability for Beam-loaded Cavity with Fast Feedback," ibid. 17. R.S. Burge, T.A. Enegren and J. Miszczak, "Amplitude and Phase Regulation of the RF Separator", Proc. 1989 Particle Accelerator Conference, IEEE (in press). 18. C.J. Oram, "Vacuum and Beam Pipe Considerations", Proc. AHF Accelerator Design Workshop, Los Alamos, February 1989 (in press). 19. W.K. Dawson et al., "A Conceptual Design for the TRIUMF KAON Factory Control System", TRI-87-1 (1987). 20. R.E. Laxdal et al., "Progress towards H" extraction at TRIUMF", Proc. 1st European Particle Accelerator Conference, Rome 1988 (in press). 21. M.K. Craddock, "The TRIUMF KAON Factory - An Overview", (these pro ceedings). -51- EXPERIMENTAL FACILITIES FOR KAON D.R. GUI TRIUMF, Vancouver, British Columbia, V6T 2A3 Canada For the purposes of the Project Definition Study (PDS) the experimental facilities at the KAON Factory must be specified to sufficient accuracy that a reasonable estimate of costs can be established. As well, the impact of the production of these facilities on the Canadian industrial community needs to be evaluated. In order to achieve these goals a number of assumptions must be made regarding the types of facilities that will be required. In an attempt to assure that these assumptions are made as accurately as possible TRIUMF is seeking advice from physicists interested in experimenting at the KAON Factory by sponsoring a number of workshops (see Table I). The philosophy behind this approach is that it will help to ensure that the contents of the experimental areas are driven by the experimental needs as they are presently foreseen. It is important though that any scheme specified at this time be as flexible as possible in order to allow for modifications in response to changes in the physics priorities that will almost certainly occur between now and the achievement of beam at KAON. Table I. Workshops 1989 Local Location Atten Organizer KAON Workshop - May 1-5 Measday Coimbra, Open Portugal Neutrino Workshop - May 14 Jennings Montreal Open Hadronic Physics at the Kaon Haiisser Bad Honnef, Open Factory - June 7-9 Germany Hypernuclear Physics - June 17-18 Gill KEK, Japan Open Spin and Symmetries - June 30- van Oers Vancouver Open July 2 KF Users Workshop - July 10-11 Page Vancouver Open Nuclear Physics with Antiprotons Kitching Italy Open In order to begin the PDS Experimental Areas Definition Study a list of the desired facilities must be made. Table II is a list, extracted from a gaze into a crystal ball of some of the physics that will be undertaken at KAON. As stated above one of the purposes of the science workshops is to ensure that this list is as complete as possible. From this list (Table II) it is learned that channels providing charged particles, K^s (fl^'s, and p's) at all the possible energies would be desirable. As well there will be need for a neutral kaon beam, a neutrino beam, muon Spin Resonance (^SR) beams and an area for extracted polarized -52- Table Ha Particle Physics A. Very Rare Kaon Decays 1. Muon number conservation (K° —» fie) 2. Searches for new effects 4(K+ -»ir+X°) B. Established Kaon Decays. 1. CP violation 2. Kobayashi-Maskawa angles 3. Form factors C. 1. i/M(i/e?) e~ scattering. 2. v oscillations 3. v masses D. Baryon Spectroscopy 1. N and A resonances (7rN scattering and reactions) 2. A and a resonances (K~N scattering and reactions) E. Meson Spectroscopy 1. ss states between 1 and 2 GeV/c2 2. Glueballs (or gluerings?) F. Hyperon-Nucleon Interactions 1. Direct scattering for An, EN, EN (tagged hyperons) 2. Final-state interactions (K~d —* 7Apn) 3. Hyperonic atoms (E-,H-,ft~) G. Antiproton Studies 1. New charmonium states via pp —* $) 2. Annihilation and baryonium 3. p scattering on nuclei and 'hot spots' H. Muon Physics 1. New (g-2) with x20 precision I. Polarization Studies 1. Polarized proton beam and target 2. Polarized effects in reactions such as ir'p —»pn Table lib Nuclear (or many-body) physics A. A Hypernuclei 1. Spectroscopy of excited states via (K~,ir~), (v+,K+) (*-,7) 2. Effective spin-orbit forces 3. Binding energy anomalies (e.g. \He) -53- 4. A lifetime in hypernuclei B. S Hypernuclei 1. Why are states so long-lived? 2. Spin-orbit forces (£Li) 3. Isospin violation C. Double Hypernuclei 1. Do they really exist? AA or E (via (I<~,x+)) 2. Relation to possible S=-2 dibaryons D. Neutron Radii in Nuclei 1. K+ and p nucleus scattering 2. Kaonic and hyperonic atoms E. Resonance Propagation 1. A(1520) behaviour in nuclear matter F. Miscellaneous 1. Regenerative amplitudes 2. Neutrino-nucleus interactions proton studies. Some of these latter studies could be done using internal targets so an area for such must also be included in the considerations. This knowledge of what might be wanted reduces the problem to one of deciding how such a range of facilities could be constructed to optimize the use of the available accelerated protons. Before proceeding with a description of a study undertaken to find this op timum layout it is instructive to ask if there are any considerations of the ac celerator design that are significant to the experimental program. The KAON accelerator complex1 consists of five rings, the Accumulator, Booster (to 3 GeV), Collector, Driver (to 30 GeV) and the Extender. It is possible to extract the beam from any of these rings; however present plans only envisage this occur ring for experimental purposes from the D or E rings. This extraction can be made at any energy between 3 and 30 GeV for the purposes of polarized proton experiments. Thus the facilities for this purpose may need to be capable of dealing with proton beams over this extensive range. Experimentalists will also be able to select from amongst the available time structures of the extracted beams that are listed in Table in. The beam extracted from the D ring will have a duty cycle of .004% (3.6 /isec/100 msec) with a microstructure of 1 nsec wide pulses every 16 nsec. This would appear to be ideal for the neutrino and some parts of the /JSR experimental programs. The beam from the E-ring will be slow-extracted beam and will be essentially DC (~85% duty cycle) where the macroscopic variations will be at 10 Hz. The microscopic structure of this beam can have the 16 nsec structure due to the 63 MHz RF of the E-ring partially eliminated. This partially flattened mode is referred to as debunched and will -54- Table III. Time Structures of Available Extracted Proton Beams. • Fast Extraction from D-Ring - Macrostructure .004% Duty Cycle(3.6 jisec/100 msec) - Microstructure Pulses every 16nsec (63 MHz RF) • Slow extraction from E-Ring - Macrostructure 85% Duty Cycle (10Hz) - Microstructure - Two Modes Available 1. Bunched lnsec wide pulses every 16nsec 2. Debunched > 50% Micro Duty Cycle have a micro duty cycle of better than 50%. The decision as to which of these various time structured extraction modes will be employed at a given time will be made on the basis of the requirements of the experiments on the floor, that is, it will be a scheduling committee task. The considerations2 to date of what the experimental facilities at KAON will look like have primarily concentrated on the secondary beams that will be produced using the full intensity (100 /i-amps) 30 GeV/c unpolarized proton beam. Figure 1 shows the layout of the areas that serve this purpose at KEK and at BNL. At both of these accelerators the primary beam is split between several proton lines some of which contain several production targets which in turn serve as sources for a number of secondary beam lines. There are various other schemes possible, for example, the one employed at all the pion factories is to place all production targets one after the other on a single proton line. It is necessary to devise a comparative scheme in order to determine which of the possible approaches is the most efficient way to employ the protons from the accelerator. A straightforward way to make such a comparison of the many options is to begin with the ideal secondary channel and attempt to devise a scheme that compromises it as little as possible. All experimentalists will agree that the ideal channel is the only channel, thus it will receive all the protons, its production target can be of optimum length (Fig. 2 shows that this is ~6.5 cm), its takeoff angle can be at zero degrees (the smallest source for secondary particles) and its acceptance can be made as large as the optical requirements will allow. A comparison study can then consider how compromises, such as putting several production targets in a line, having several channels viewing the same produc tion target and splitting the proton beam in varying proportions, would effect the efficiency of this ideal channel. A recent study along these lines by Beveridge and Doornbos2 considered an experimental arena containing six (6) charged sec ondary channels and a neutral kaon channel. They started with ideal channels, -55- 2 ^& 12GeV-PS KEK-PS Beam Lines. ACS EAST EXPERIMENTAL AREA PROPOSED EXPERIMENTAL ARRANGEMENT PT ltll Fig. 1. KEK and BNL experimental areas -56- examples of which are shown in Fig. 3a for high energies, and Fig. 3b for low energies. —r—i—r P' U6GIV/C TARGET TWCKNESSIcml Fig. 2. Length versus yield from Yamamoto (Ref. 3). Figure 4 shows several schemes for extracting low energy beams from a pro duction target that will allow for the extraction of several other beams from the same target. All of these schemes compromise the acceptance of the channel as is documented in Table IV where the uncompromised version appears in the last column. The other major effect of these schemes is that the takeoff angles for the beams is no longer at zero degrees. This means that the source of the particles will be large in the horizontal direction, for example a 6.5 cm target viewed at 10° will be a 1 cm long object (in addition to the width of the proton beam). A possible solution to this problem is the vertical momentum analysis scheme employed at LAMPF but the need for electrostatic and RF separators may make such an approach prohibitively difficult. Any experimental layout that places several production targets in the same proton beam must attempt to optimize particle production versus the -57- 22.5" for K.55 or K.75 Fig. 3. a) High energy "ideal" channel and b) low energy "ideal" channel. Table IV. Solid Angle Acceptance for Different Take-off Schemes P Septum Bend Maxim Semi-maxim Quad Gev/c (msr) (msr) (msr) (msr) at 0° 0.55 4.0 5.3 3.6 5.3 8.0 0.75 4.0 4.7 3.6 4.7 8.0 1.50 1.48 1.72 1.65 1-57 2.36 2.50 0.62 0.68 0.55 0.59 0.75 transmission of the primary beam through the upstream targets. The problem of reconstituting and transporting the beam after it has passed through one of these targets must also be taken into account. Beveridge and Doornbos2 using the results of Yamamoto ei al.3 studied particle production versus transmission for the case in which a target of 6 cm length (approximately ideal) is preceded by -58- a) Production Target proton beam Fig. 4. a) Septum scheme b) for low energy channel; b) bend scheme for low en ergy channel; c) MAXIM Production scheme for two low energy Target channels; d) semi-MAXIM bend' original scheme for two low energy proton beam proton beat must be axis channels. restored to original oxis MAXIM c) Production Target Proton Beam WK2.5 SEMI-MAXIM Production Target > Functions as one bend only system for K.55 or K.75 and as MAXIM for K1.5 or K2.5. The rays exiting B3 seem to go straight through the production target. -59- another target. They determined that the efficiency of a pair of targets was best if the first target was approximately 3 cm in length. Assuming that the efficiency for restructuring the beam after such a target can be 100% they examined the three possible layouts of six charged and two neutral channels shown in Fig. 5. THE THREE LAYOUTS a) TO.55 T, /0-75 \6.00 * 1.15.0 b) K* T /Future 3\Channels _ fO.55 _ fO1.7. 5 Ti \ 1.50 TZ12. 50 [6.00 p.,0 0 Fig. 5. Test layouts. In Fig. 5a it is assumed that the primary proton beam is split two ways and that only two secondary channels will be taken from any of the production targets. This allows the takeoff angles for the .55 and .75 GeV/c beams to be at 0° when they are combined with the 6.0 and 15 GeV/c beams respectively. All these channels therefore meet the optimization requirements described above regarding solid angle and source size. In this study the 1.5 and 2.5 GeV/c beams are compromised by being combined in a MAXIM scheme. In Fig. 5b it is again assumed that the proton beam is split two ways while in Fig. 5c it is not split. In both 5b and 5c the channels are combined as shown using a SEMI-MAXIM scheme for the lower energy channels. The targets for the charged particle channels in the case of Fig. 5c are both 3 cm in length. The arrangement of Fig. 5b has the advantage that future expansion at target 3 is possible while in the meantime the neutral kaon channels can be operated independently of the charged channels. -60- Table V lists the factors by which each of the channels has been compromised in order to achieve the arrangements shown in Fig. 5. Here, as compared to Ref. 2, the Kl.5 and K2.5 channels in setup A are considered to be compromised relative to their ideal arrangement. Here also where targets have been shortened relative to the ideal case that factor has been included in the calculation of the efficiency of the channels viewing it. The product of these compromise factors is shown in the final column for each setup. The sum of the final efficiencies for each channel is the efficiency of that entire scheme. Of course in either of the split proton beam schemes the split factor can be varied in an attempt to maximize productivity.' A 50/50 split has been assumed here and a decision to use any other ratio left, like that of selecting the time-structure of the beam extracted from the accelerator, as a task for the scheduling committee. From Table V it appears that the arrangement in which the three targets are on a single proton line is the most effective way to employ the proton beam. However this efficiency advantage is not considered to be sufficient to overcome the fact that in this scheme these channels are far from ideal and the operational coupling between all the channels is maximized. It has therefore been decided that the layout shown in Fig. 5a, being the one with the largest number of ideal channels and the greatest flexibility, is the one that will be constructed. Fig. 6 shows how this scheme would appear and what the building to contain it will be. K° AREA Fig. 6. KAON experimental facilities. In conclusion a scheme for the layout of the secondary beams has been selected and the building sized. Cost estimating for the magnets, shielding, 61- Table V. Compromised Factors for Test Setups Case A Ratio of Compromised Factors to Ideal Factors Channel Momentum Solid Angle Target Length Product Range K(.55) 0.40 - 0.55 1.0 0.72 0.50 0.36 K.75 0.55 - 0 .75 1.0 1.0 0.28 0.28 K(1.5) 0.75 - 1.5 0.7 0.72 0.50 0.25 K(2.5) 1.5 - 2.5 0.73 0.72 0.50 0.26 K(6.0) 2.5 - 6.0 1.0 0.72 0.50 0.36 K(15.) 6.0 - 15.0 1.0 1.0 0.28 0.28 K° 7.0 7.0 0.28 0.28 SUM 2.07 CaseB Ratio of Compromised Factors to Ideal Factors Channel Momentum. Solid Angle Target Length Product Range K(.55) 0.40 - 0.55 0.66 0.72 0.50 0.24 K(.75) 0.55 - 0.75 0.59 1.0 0.28 0.16 K(1.5) 0.75 - 1.5 0.70 0.72 0.50 0.25 K(2.5) 1.5 - 2.5 0.73 1.00 0.28 0.20 K6.0) 2.5 - 6.0 0.66 0.72 0.50 0.24 K(15.) 6.0 - 15.0 1.00 1.00 0.28 0.5 K° 0.66 7.0 7.0 0.5 0-28 SUM 1.00 1.87 CaseC Ratio of Compromised Factors to Ideal Factors Channel Momentum Solid Angle Target Length Product Range K(.55) 0.40 - 0.55 0.66 0.72 1.00 0-48 K(.75) 0.55 - 0.75 0.59 0.72 0.55 0.23 K(1.5) 0.75 - 1.5 0.70 0.72 1.0 0.5 K(2.5 1.5 - 2.5 0.73 0.72 0.55 0.29 K(6.0 2.5 - 6.0 0.66 0.72 1.0 0.48 K(15.) 6.0 - 15.0 1.00 0.72 0.55 0.30 K° 7.0 7.0 0.30 0.40 SUM 2-68 -62- building and building services are now under way. The list of tasks related to defining the experimental facilities at KAON that are shown in Table VI still require a substantial amount of effort before the PDS can be declared complete. This list is extensive and there are many places where our colleagues interested in experimenting at KAON can help us. The workshops discussed above are one way in which people are encouraged to input their ideas but private communi cations are certainly welcome. Table VI. Tasks Still Requiring Input • Polarized Proton Beam Area — All Energies Needed? — Spectrometers • Internal Targets — Site Definition — Spectrometers • Neutrino Facility — Site Definition — Detector System • Kaon Spectrometers and/or Detector Facilities — Floor Space Required — Compatability of Kaon and Hypernuclear Systems — High Resolution Versus Acceptance • Production Targets — Radiation Hardening of Magnets etc. — Remote Handling Capability • Proton Beams Downstream of Production Targets — Beam Reassembling Versus Bypass REFERENCES 1. M.K. Craddock, (these proceedings). 2. J. Beveridge and J. Doornbos, TRI-DN-89-K19. 3. A. Yamamoto, Study on Low Energy Intense Kaon Beam K2, Thesis, KEK. -63- EEE-PS Beam Channels at Present and New Experimental Halls K. H. Tanaka Beam Channel Group, Physics Department HI, KEK, National Laboratory for High Energy Physics, Oho 1-1, Tsukuba-shi, Ibaraki-ken, 305 Japan 1, Present (East) Experimental Hall I do not talk about beam lines at the present experimental hall. Please request " KEK-PS Users Guide Book" CI] to the KEK-PS Experimental Planning and Program Coordination (EPPC) Division. Most parameters of beam lines can be found in the book with fine photographs and/or drawings. Professor Nakai, head of EPPC, is responsible to the book. 2, New (North) Experimental hall A new counter experimental hall [21 is now being constructed at the KEK 12 GeV Proton Synchrotron (KEK-PS). The completion of the building of the new hall is by the end of this year and is immediately followed by the magnet setting on the new external proton beam line, which will supply primary protons from a new extraction point of the KEK-PS to the new hall. The beam handling system of the new hall has been designed against lxlO'3 pps (protons per second) in order to accept full proton beams extracted from the upgraded KEK-PS. This beam intensity is almost one order of magnitude greater than the present level of the KEK-PS, 1x10 ,a pps, and will be realized in near future in connection with the Japanese Hadron Project (JHP) [31. All the magnets for the new external proton beam line were manufactured with new technology we developed for JHP era [41 and are now ready for installation. A schematic illustration of the new hall is shown in Fig. 1. The primary proton beam will be split into two ways A and B by a set of Lambertson type magnetic septa. The proton beam at the line A will hit two production targets in cascade. The low momentum (up to 600 HeV/c) separated beam channel K5 C5] will be supplied secondary particles from the upstream target. The downstream target will supply secondary particles to the medium momentum (0.5 — 2 GeV/c) and high resolution «0.15O separated beam channel K6 C63. Magnets, power supplies and DC separator for K5 have ~64- already been prepared and are waiting for installation. The expected performance of K5 is summarized in Table 1. K6 is the final stage of its design. The primary beam line B will supply protons to experiments which will require full and clean primaries Fig. 1. A schematic illustration of the new counter experimental hall of the 12 GeV KEK-PS. For the cascade targetting, we developed a new scheme of primary beam transport, the beam swinger optics (BSO). Since the emittance of the beam passed through the first target grows very rapidly, the most important point for the successful cascade targetting is to place the downstream re-focusing quadrupoles as close as possible to the first target. The longer distance between the target and the Q's requires the larger magnet aperture of Q's. Therefore we decided to swing the primary protons before the first target by a set of bending magnets (BS1, BS2) as shown in the upper half of Fig. 2. The beam will be swung back to the correct optical axis by the first bending magnet of secondary beam line (Dl) and a small dipole magnet (BS3). If we would try to swing back the primary beam by three dipoles placed at the downstream of the target as shown ir. the lower half of Fig. 2, the aperture and the length of re-focusing Q's, and also the aperture of correction dipoles, would become very large compared with ones of the new scheme, i.e. BSO. It should be noticed that we will give up the zero degree production at the first target for the BSO. The production cross sections of the secondaries are, however, almost flat against the production angle at around the zero degree in the low momentum region. If the momentum of the secondary beams provided by the first target is low enough, we loose only a very small fraction of the secondary particles and get a successful operation of the -65 — cascade targetting. This is a reason why the low momentum beam channel, KS, is connected to the first target. By use of BSO, the transport efficiency from the first target to the second target is expected to be over 9SX for the residual protons passed through the first target. D 1 Three Dipoles Fig. 2. The beam swinger optics (BSO, upper half) and the traditional beam swing back system by using three big dipoles at the downstream of the target. The negative charged particle is selected for the secondary beam channel. Two versatile spectrometers are under construction for the new hall. Toroidal spectrometer[7], which is designed and constructed by Meson Science Center, University of Tokyo, will be placed at K5 experimental area and a study of hypernuclear spectroscopy using stopped negative kaons, and/or a search of rare decay modes of charged positive kaons, will be carried out. The superconducting kaon spectrometer SKS [6], which is prepared by Institute of Nuclear Study, University of Tokyo, will be settled in the experimental area of K6. High resolution spectroscopy of pion, kaon and antiproton induced reactions will be performed by using the combination of beam channel K6 and spectrometer SKS. The works presented here are group efforts of the KEK-PS Beam Channel Group conducted by Prof. H. Takasaki. The author would like to express his thanks to members of Beam Channel Group. -66- References 1) KEK-PS USERS GUIDE BOOK, available at FPPC division, KEK 2) K. H. Tanaka, Nuclear Physics A450, 553c. 3) Japanese Hadron Project, available at INS, University of Tokyo. 4) K. H. Tanaka et al., KEK preprint 89-82, to be published in the proceedings of 11th International Conference on Magnet Technology. 5) K. H. Tanaka and M. Takasaki, K5 Design Parameters, Beam Channel Group Engineering Note (unpublished) 6) T. Nagae, M. Ieiri, KEK-Report 89-6, p259-275 7) R. S. Hayano et al., KEK-PS research proposal E-130. Table 1. Expected secondary particle yields (600HeV/c) of K5 for 10 la protons on 6 cm Pt target. K + / K _ 780 x 103 / 280 x 103 n + / 7i 390 x 10° / 310 x 10° P / "p" 400 x 10° / 4.8 X 103 -67- 89-f-kitchln,talk/apl2 Nuclear Physics at the KAON Factory P. Kitchlng In the limited time available to me I will only be able to briefly survey the range of nuclear physics issues which can be addressed with a high intensity hadron facility such as the Kaon Factory. The range of topics I will attempt to cover is-listed below. 1. Introduction. 2. Hadron spectroscopy. 3. Kaon scattering. 4. Hypernuclear physics. 5. Spin physics. 6. Nuclear physics with neutrinos. 7. Conclusions. I am defining Nuclear Physics rather broadly, to encompass the study of strongly interacting systems, and Including: - the structure of individual hadrons - hadron-hadron interactions - hadronlc weak and electromagnetic currents (in nuclei too) - conventional nuclear structure - exotic nuclei. The basic theme of my talks will be how the Kaon Factory can shed light on non-perturbative QCD and its relation to conventional nuclear physics. He are at an important juncture in strong interact ton physics in that we have a theory (QCD) which is probably correct but which is so intractable that even the one-nucleon problem is beyond calculation at the present time. If we look back in the history of nuclear physics we see that the 1950"s and 60's were dominated by the interplay between the collective model and the shell model of the nucleons, in other words between the role of nuclear matter and nucleons in the nucleus. The 1970"s and 80*s 3aw th issue of mesonic exchange currents and "non-nucleon" exotic particles in nuclei emerge, with the role of it's and A's as nuclear constituents. Now and in the near future we see the question of the role of quarks in nuclei come to the forefront i.e. what are the relevant degrees of freedom in nuclei? Can we continue to think of nuclei as made up of protons and neutrons (with a few it's and A's thrown in) as are these nuclear phenomena which will force us to take the underlying quarks and gluons into account explicitly? After the general introductory comments let me now turn to some concrete examples, the first one of which is Hadron Spectroscopy. However I will not discuss conventional hadrons, pure glue states and hybrids which were extensively discussed by the speakers yesterday, except to remark that a recent theoretical paper1 stated that -68- "Twenty five years after the birth of the quark model, light meson spectroscopy 13 In deplorable shape". A3 an example, aside from the tensor mesons, of the 27 L=l mesons, only 4 or 5 are reasonably well understood. This Is a rather shaky foundation on which to base our understanding of QCD. While we don't have to understand all the details, at present we know too little to even verify the overall picture. Let me emphasise again that we are talking about non-perturbative QCD i.e. the physics of confinement. The particular issue I wanted to raise which was not discussed yesterday is that of Multiquark States. It seems not unlikely that one can make K-K or K-N "molecules" which are loosely bound, rather like the deuteron Fig. 1(a)). At various times it has been suggested that the f„(975) and the + G0(980) are 1=0 and 1=1 members of the J=0 state of such a K-K "molecule" and that the ^(1*20) is the 1+ part. The 3ad state of light meson spectroscopy referred to earlier does not allow us to say right now whether this interpretation is correct or whether f0, aQI fj can all be accommodated within the conventional framework. One way which might enable us to tell would be to study the production of K-K "molecule" candidates as a factor of A. The multiquark state is presumably more fragile than qq states and would therefore have a shorter mean free path in nuclear matter. To summarize the situation for hadron-hadron forces, at short distances one can model gluon dynamics by simple one gluon exchange but at large distances one does not know what to do. The Nucleon-nucleon force has been studied by nuclear physicists for more than 50 years, but to really understand it we probably have to go outside the N-tJ system. As a first step we need systematic study of low energy meson-meson interactions (itit,nK, irq etc). This 13 a good testing ground for quark exchange forces which might be the most effective way of Improving our understanding of nuclear physics. I want to emphasize that the spectroscopies of qq, qqq, hybrids, glueballs and NN are all indivisible - they are all governed by the same underlying theory. I would now like to turn to kaon scattering and will discuss the IC+- nucleon scattering and interaction and K*- nucleus scattering. Let me begin by reminding you of the difference between the K+-N and K~-N interactions - the former is much weaker than the latter because of the Impossibility of forming S-channel qqq resonances from K^N (the K"1" contains u and K~ u) (Fig. 1(b)). Resonances In K+N would necessarily involve 5 quarks (Z*) and the existence of such objects is still controversial. Me need better K+fi date in the 1-2 GeV/c region to resolve this controversy. This points up the fact that the K-N data base is still poor. There are ambiguities in the phase shifts, polarization data are scarce (no K-S data for p < 1 GeV/c) and -69- there Is no spin rotation data at all. Figures 2a and 2b show three different phase shift solutions, together with the available cross section and polarization data at 500 MeV. As you can see the data are quite unable to discriminate between the possible solutions. If we examine the spin rotation parameter Q, however, (Fig. 2c) we see large differences between the three solutions which could easily be resolved in less than 1 day of running at the Kaon Factory. It Is important to improve our knowledge of the K+-N interaction not just for its own sake, but also because doing so will enable U3 to use the K+ as a probe of nuclei. The lack of resonances in the K+N interaction means that the low energy K+ has a very long mean free path Is nuclear matter, longer than any other hadron (Figure 3). The K+ can therefore be looked upon as a "heavy electron," with the following list of advantages as a nuclear probe: - it is weakly interacting ao It can reach the nuclear interior - it has no known resonances (such as irN+A) - inelastic channels are not open or are negligible - there is no annihilation channel - there is no particle identity problem (such as in N-nucleoa) leading to there being no exchange Interaction - the t approximation should be good and estimates of V™L reliable - medium modifications are absent (unlike N-nucleus) - high momentum transfer is possible with KN still elastic - the cross section return K*'n/K+p goes through unity at p =» 500 MeV, enabling one to change the sensitivity to neutrons or protons by varying the momentum. As an example, I will now consider the application of the K+ probe to an old problem in nuclear physics, the derivation of neutron densities in nuclei. Proton densities as determined by electron scattering do not agree with the best Hartree-Fock calculations at the centre of heavy nuclei2, while there are no reliable determinations of neutron densities in spite of many years of effort using intermediate energy protons and a particles. A recent paper3 comparing the sensitivities of K+ and protons needed the conclusion that K+ are about equal to protons at the surface and 5 times better In the nuclear interior. This is obviously a consequence of the long K+ mean free path in nuclear matter. Figure 4 shows the effect on the ratio of the differential elastic cross sections of 160 to 180 for 50 MeV K+ of changing the neutron density radius of 160 by 10%. It Is clear that K"1" elastic scattering at the larger angles will be an extremely sensitive way to measure neutron densities. Most of the problems (see Table 1) associated with nucleon-nucleus scattering either do not exist or are much reduced for the IC*". A logical approach to utilizing Its desirable properties Is outlined in Table II, where one starts by delineating the low energy K-N phase shifts, tests one's understanding on deuterons and (A=Z) nuclei (where neutron distributions are presumably known) before attacking the more difficult general case. One could then attack the neutron transition densities using inelastic scattering. Finally, two other reactions would be of great interest. The first is the use of the (K+.p) reaction to search -70- for narrow S=+l states (so-called hyponuclei). The second is nucleon knockout, ACK+.K^N) where the long mean free path of the kaon should enable one to access deeply bound shell model hole states, particularly neutron states, which are probably not accessible in any other way. All of this has been known for many years and one might ask why so little progress has been made. 1 think the answer Is that the Inadequate K4- beam intensities available in the past have meant low count rates, thick targets, poor energy resolution and poor statistical accuracy. All this would change with the advent of the Kaon Factory, which would revolutionise this type of study. I would like to consider now the field of hypernuclear physics. There are many open questions including: - the nature of the Hyperon-nucleus potential and its relation to the Uyperon-nucleon interaction - the impact of the Pauli Exclusion Principle and the nature of deconfinement (Figure 5) - the behaviour of the s-quark in the nuclear environment - the weak decay of the A mode nucleus through the process A+N •*• N+N - the status of 2, hypernuclei - the existence and properties of doubly strange hypernuclei - the effects of the hyperon on the macroscopic properties of the host nucleus such as its radius, magnetic moment etc. Two basic reactions have been used to investigate hypernuclei, the (K~,it~) reaction and the (it+.ld") reaction. The characteristic features of each are summarized in Table III. (VL~,iC) studies have been confined to light nuclei, whereas (n+,ICf) has been used up to 209Bilf. Only low-lying states have been observed, with energy resolutions typically 3-5 MeV, utilizing small acceptance spectrometers. From 1990 onwards the new KEK experimental hall, with its new beam lines and superconducting spectrometers will open up a new era in this field, with energy resolutions approaching 1 MeV and very large acceptance spectrometers. We would expect that the Kaon Factory era, beginning hopefully around 1995, will lead to even greater progress, with higher quality, more intense beams and developments in instrumentation giving energy resolutions of at most a few hundred KeV. Higher intensities will also make coincidence measurements much easier, enabling us to study the decay of hypernuclei. For example it has recently been suggested5 that both the (n+,K*) and (K~,ic~) reactions, with incident beam energy of order 1 GeV/c, can produce spin orientated hypernuclei in which the intrinsic spin of the A is also well polarized. If this turns out to be true, and an approved experiment at KEK will soon test these ideas, then angular correlation studies of y-rays and weak decay particles from polarized hypernuclear states may open up a new field of hypernuclear spectroscopy. Information on electromagnetic moments or weak decay mechanisms might be obtained in this way. -71- The higher beam intensities available from the Kaon Factory will also be essential for producing doubly strange hypernuclei via the (K'.K1-) reaction. Only a few events of this type have ever been seen, all in emulsions, because of the extremely low cross sections involved. Such experiments can give vital information on AA and = N interactions. Experiments to search for the doubly strange H-dibaryon, predicted to be a bound state because of its high degree of symmetry, are also intensity limited. One such search has just completed data taking at KEK (E176) and we will hear more about it later today. Another will start soon at B.M.L. (E813). Even if the H is found in these experiment's, detailed study of its properties must await higher beam intensities. For instance, it has been suggested that the H is large in physical size, because it is weakly bound. Study of its production rate as a function of atomic number, A, might give information on its transmission through nuclear matter, which would be very interesting. I want to turn now to the subject of spin physics at intermediate energies, where large and unexpected effects have been seen. For instance, the structures in Ao^ and Aoij. in p-p elastic scattering first seen at the ZGS have been interpreted as evidence for dibaryons, although the subject is still clouded by controversy. The high degree of polarization seen is inclusive A production at several laboratories is not at all understood. 2 Finally the structures seen in both Ay and Ayy in high P j_ elastic proton-proton scattering (Figure 7(b)) still defy explanation. The difficulty is that perturbative QCD predicts that all such polarization effects should be zero. This kind of experiment may therefore teach us about constituent wave functions and parton dynamics on the region between Perturbative QCD and confinement. He should therefore push to the highest possible p2i in the hope of seeing the onset of Perturbative QCD behaviour in spin observables. Cross sections are however falling rapidly (5 or 6 orders of magnitude between 10 GeV/c incident energy and 30 GeV/c, at around 90s in the cms). (Figure 7(a)). Thus beam intensity may again become an important factor. At present the AGS has 1.5 nanoaraps of polarized protons up to 18.5 GeV/c, and the upgrade should boost this to 30 nanoamps. TRIUMF now accelerates about 1 u,amp with 707. polarization and we are commissioning a source to give several uamps. The Kaon Factory is being designed to accelerate all of its beam to 30 GeV/c with little polarization loss (< 15% estimated). We need also to develop polarized targets able to withstand higher beam intensities, and to Investigate the feasibility of using gas jet internal targets. Finally, I want to mention the use of neutrino beams from the Kaon Factory as nuclear probes. Three possibilities have been suggested. Firstly, it has been pointed out6 that there exist a whole class of axial form factors which are not accessible to the electromagnetic interaction. If beam intensities are high enough it may turn out that the Kaon Factory becomes an axial CEBAF. Secondly, measurements of v and v electric scattering at low Q may be the best way to probe the spin content of the proton, a topic of great current interest, as John Ng haa already described. Finally, neutrons may be used to search for Second Class Currents, which are zero in the Standard Model but finite in some broken symmetry models. Wilkinson7 has -72- pointed out that It Is possible to Identify neutrino Induced nuclear transitions to well-defined final states that are almost unambiguous signals 16 + 16 of Second Class Currents. The example given Is 0(ve,e ) NQ_ where the 16 8 final N state Is the J* =» 0~ state at 0.120 MeV . With Ev =• 500 MeV and a momentum transfer of 400 MeV/c the cross section (for the ratio of Second Class tensor to first class weak magnetism equal to 0.1) Is about 100 times greater than for no Second Class currents. Such experiments are obviously very difficult but the reward would be great. The experimental feasibility of these suggestions should be assessed for the Kaon Factory. We are holding a workshop on May 14 In Montreal to do just that. To conclude, there are many Important, timely nuclear physics questions a Kaon Factory can answer. The key will be systematic studies using different probes and variable momentum transfer. The Kaon Factory complements other nuclear facilities being built or planned, such as the Japanese Hadroa Project, CEBAF and RHIC. Acknowledgements In the preparation of this talk I am deeply Indebted to Otto Hausser, Steve Godfrey and Tony Thomas for Ideas and discussion. References 1. Isgur, Mornlngstar and Reader, Phys. Rev. £ (in press). 2. B. Frol3, Lecture Notes In Physics 108. 3. Coker, Lumpe and Roy, Phys. Rev. C3l"Tl985) 1412. 4. P.H. Pile et al., 1988 Int. Symposium on Hypernuclear and Low Energy Kaon Physics, Legnaro, 1988. 5. H. Ejiri, T. Kishlmoto and H. Nouml, Osaka Univ. preprint OOLINS 88-12. H. Bando, T. Motoba, M. Sutona, J. Sofka, Phys. Rev. C39, (1989). 6. T.W. Donnelly and R.D. Peccel, Phys. Rept. 59j, 1, (19757. 7. D. Wilkinson, TRI0MF report TRI-DN-88-K4, 1988. 8. T.W. Donnelly and J.D. Walecka, Phys. Lett. B41, (1972) 275. -73- Figure Captions Fig. 1. (a) Weakly bound systems, the deuteron and postulated K-K molecule. Fig. 1. (b) The K~N and K+N systems. Fig. 2. (a) Three allowed phase shift solutions and measured values of (a) der/dfi = |f|2 + |g|2 Fig. 2. (b) P =« 2 Im (fg*)/do-/d£J. Fig. 2. (c) The predicted value of Q =» 2 Re(fg*)/dcr/dQ is shown In (c) for the three solutions together with the estimated measurement error attainable in less than 1 day of running at the Kaon Factory. Fig. 3. Mean free path (X) in nuclear matter for hadrons. Fig. 4. Ratio of differential elastic cross sections of 160 to 180 for K+ at 50 MeV. The solid line represents the standard set of parameters and densities; the dashed line has a 10% change in the neutron density radius of16 0. Fig. 5. (a) Possible single-particle orbitals for nucleons and for a hyperon. The nucleon orbitals are occupied up to the Fermi surface, while the hyperon orbitals are unoccupied. Fig. 5. (b) Quark structure of a simple hypernucleus jJHe. The u and d quarks In the nucleon clusters fully occupy the ground orbital, while the s quark In a A can sit in the same orbital, the other u and d quarks cannot. Fig. 6. Plot of the analyzing power A and the spin-spin correlation parameter Ayy as functions of momentum transfer squared for proton-proton elastic scattering at 18.5 GeV/c. The error bars include both statistical and systematic errors. The dashed lines are hand-drawn curves to guide the eye. Fig. 7. (a) The ratio of spin parallel to spin ant1parallel differential cross section as a function of P| for p-p elastic scattering. Squares indicate 90° measurements at various energies; dots represent measurements at various angles up to 90° at 11.75 GeV/c. Fig. 7. (b) The large angle p-p elastic scattering differential cross section as a function of incident momentum. -74- Table I Problems with Proton-Nucleus Scattering (1) — the surface character of the Interaction (2) — the density dependence of the interaction (3) — strong medium modifications (4) — antisymmetrization, exchange forces (5) — tensor components of the interaction (6) ~ Paull blocking effects (7) — It is difficult to do a self-consistent treatment of all of the above. These problems either do not exist for ^-Nucleus, or are much reduced. -75- Table II A possible K+ experimental program System Measure Remarks K+S-K+p a P Q K*a>K+n o-P (Q) use J (3He) target quaslfree kinematics, NTOF K+3+ K d 1T11> T20» T2l» T22 test of "exact" calculations N=Z ^.^elastlc test reaction mechanism + + A(K ,K )elagtlc deduce neutron distributions ^^•K4"') inelastic deduce neutron transition densities, collective + 2 1,3~1 surface peaked + 2 2 peaked In interior. -76- Table III Hypernuclear Physics-Techniques Elementary 2500 ub/sr 500 ub/sr Cross Sections Bean Intensity 10 10 (Purity) (1:1) very high Kaon ra.f.p. 1-2 fm 5 fm Momentum small large Transfer Physics mainly probes preferentially "subs ti tutlonal" excites high spin states near the deeply bound states, Fermi surface. can produce spin polarised hypernuclei. -77- 0© 0© n p K K DEUTERON K-K MOLECULE (a) S=-1 S=+1 (b) fig.l -78- 1.2 + in I.I h K -P v. .a 1.0 502 MeV E 0.9 C3 0.8 SOL. I •o SOL. 2 b 0.7 SOL.3 XJ _L I I I L 10 20 30 40 50 60 70 80 90 0cm(deg) 1.0 1—r 1 IT—I T K+-p 0.8 506 MeV Q_ 0.6 0.4 - SOL. I SOL. 2 0.2 - SOL.3 _L_I I L J L 10 20 30 40 50 60 70 80 90 0cm (deg) O 30 40 50 60 70 80 90 0cm(deg) -79- 200 400 600 800 PAa (MeV/c) LAB fig.3 120 150 cm fig.4 -81- • -.Well—confined" Experimentally J^juark cluster"* accessible Experimentally J Oeconflned _». Inaccessible :=y=d quark cluster :--W/ 7 HYPERON NUCLEON (a) • u-quark O d-quark © s-quark 1/2 3/2 1/2 p p n n "t> fig.5 -82- \ • Court et al. _ 10 - z • This Exp. IS \ 18.5 GeV/c < I «sr \ ?io A f < o t 6 P2 (GeV/c)2 fig.S -83- (a) 30 10' 6 I 1 1 Adcr/dt 0 90° 10-3 1 - Xk • 80° - OJ pp-»pp « 10 "32 l\j (VI -33 g 'o > I0"34|- - b dcr/dtxO.I 10 •35 8- 80°\ \0 = 9O° ~ 10' 36 1 1 10 20 31 P (GeV) (b) LAB x ' T T 7 6 p + P-vP + P 5 \ o90cm I4 • ll.75GeV/c S 3 o Q. 'I 2 b : .^..^0-°-----^ 0 P* (GeV/c)2 fig.7 -84- NUCLEAR PHYSICS AT THE JHP K ARENA Tomokazu Fukuda Institute for Nuclear Study, University of Tokyo Tanashi, Tokyo 188, Japan 1. Introduction The 12-GeV PS at KEK provides us a unique opportunity to explore the intermediate-energy nuclear physics with K and K mesons. Only one competitor is the AGS at BNL, but it is headed for the relativistic heavy-ion physics. Hence the KEK PS is expected to play an important role before the KAON factory era by developing the relevant physics and technology. Keeping this in mind, gradual upgrade of KEK PS is being carried out. It is also planned that a low-emittance H~ beam will be injected into the present PS from the JHP 1-GeV linac, which corresponds to JHP K Arena. This modification of the injection scheme of the PS is expected to increase the proton beam intensity from the present value of 4xl012 ppp to 2xl013 ppp. In this report we review the present and future activities of nuclear physics at KEK PS and describe the upgrade program under progress. The details of JHP will be discussed by T. Yamazaki in this proceedings. 2. Present and future activities Many efforts have been focussed on the study of physics with strangeness S= -1 and -2. At KEK, the (stopped K;n) and (7c+, K+) reactions are used to produce hypernuclei with S= -1 instead of the traditional method of recoilless production of hypernuclei. Those methods preferentially excite deeply bound hypernuclear states -85- and/or high spin states, and will enable us to study the properties of hyperon embedded deeply in the nucleus. An interesting finding is a bound state of S+/Z° in the 4He(stopped K-,7C~) reaction [1], whose binding energy and width are 3.2 MeV and 4.6 MeV, respectively (Fig. 1). The observed width is surprisingly narrow in view of the large 2N-» AN conversion. The presence of the narrow bound state is attributed to the strong spin-isospin dependent repulsive potential which tends to push the E away from the nuclear core [2]. It is also suggested that a halo-like hybrid bound states of 2- may exist in a Coulomb pocket [2], as considered by Yamazaki et al. [3], where the repulsive core potential is balanced by the long-range attractive Coulomb potential. This phenomena and, in general, whether 2 hypernuclei with narrow widths exist or not are one of the most interesting problems. Another intriguing finding is a copious production of light A- 4 hypernuclear fragments like AH in (stopped Kr,n~) reaction, which is interpreted as one through "hyperon compound process" [4-6] (Fig.2). This consideration indicates a possibility to study hypernuclei by measuring discrete pion spectra resulting from hypernuclear weak decay, without measuring the formation pion. These above studies will be efficiently performed by using a new superconducting TOROIDAL spectrometer [7], which is characterized by a high resolution (1 MeV/c FWHM), a wide momentum range (100-300 MeV/c) covering pions of A formation, Z formation and weak decay of A hypernuclei simultaneously, and a large solid angle (10% of 4TC) (Fig. 3). The associated production reaction, (7t+,K+), is the reaction suitable for a general study of hypernuclei throughout the periodic table. It is the best method capable of accessing bound states of heavy nuclei, because its large momentum transfer is well matched to the reaction in which a neutron in high-/ orbit is converted to a hyperon in low- lying low-/oribits [8,9]. Recent experiments at BNL and KEK [10,11] showed shell structure of A hypemuclei up to 89Y (Fig.4). A possibility to produce polarized A hypernuclei by (JC+, K+) reaction is discussed and being pursued [12,13]. This will open up a new era of -86- hypernuclear spectroscopy such as measurements of weak decay, hypernuclear y-rays and magnetic moment of A hypernuclei [14]. These studies will be extensively performed by a new Superconducting Kaon Spectrometer (SKS) [15] (Fig. 5). It is designed to detect forward going reaction particles around 1 GeV/c with high momentum resolution of Ap/p=10-3 and large acceptance of 100 msr. The SKS consists of a sector-shaped superconducting magnet and a compact detector system for triggering and tracking, resulting in short flight path of 5m indispensable for K meson detection. The spectrometer will also be used for studying Z hypernuclei via (rc, K+) reaction as well as various pion induced reactions, such as (it*, rc*) and (n ±, rc +), at energies well above the A region. In order to handle higher intensity protons a new experimental hall is now under construction (Fig. 6). The following four beam lines are to be installed in the new experimental hall. (1) K5 beam line: low-energy K/rc/p beam line (< 0.6 GeV/c), (2) K6 beam line: intermediate-energy K/rc/p beam line (0.5-2.0 GeV/c), (3) K0 beam line: neutral beam line, (4) rcu, beam line: low-energy iz\i beam line (< 0.3 GeV/c). The TOROIDAL and SKS will be installed in the K5 and K6 experimental areas, respectively. Nuclear physics with S= -2 are also interesting and challenging. At KEK, search for double hypernuclei and H particles has been carried out by using hybrid emulsion technique, i.e. emulsion combined with triggering and tracking detectors [16]. This study will be extended by the next-generation detectors for vertex reconstruction and 4jc-type spectrometer with high momentum resolution [17,18]. Physics by using high intensity secondary beams will be done at the new exprimental hall, while those with primary beam and medium intensity secondary beam will be carried out in the present (old) experimental hall. Indeed physics with polarized protons and with secondary beams from internal target have been actively pursued [19]. As are discussed here, we have a wide variety of -87- research fields and experimental techniques. In this sense KEK-PS is a really nice playground of intermediate nuclear physics towards next-generation facilities like KAON. References 1. R.S. Hayano et al., Nuovo Cimcnto 102 (1989) 437. 2. T. Harada, S. Shinmura, Y. Afcaishi and H. Tanaka, Nucl. Phys. to be published. 3. T. Yamazaki, R.S. Hayano, 0. Morimatsu and K. Yazaki, Phys. Letters 207 (1988) 393. 4. T. Yamazaki, Nuovo Cimento 103 (1989) 78. 5. H. Tamura et al., Phys. Rev. C40 (1989) 479. 6. H. Tamura et al., Phys. Rev. C40 (1989) 483. 7. T. Yamazaki et al., Nuovo Cimento 102 (1989) 695. 8. C.B. Dover, L. Ludeking and G. E. Walker, Phys. Rev. C22 (1980) 2073 9. T. Motoba, H. Bando, R. Wunsch and J. Zofka, Phys. Rev. C38 (1988) 1322 10. R.E. Chrien, Nucl. Phys. A478(1988) 705C. 11. M. Akei et al., Nuovo Cimento 102(1989). 12. H. Ejiri, T. Fukuda, T. Shibata, H. Bando and K.-I. Kubo, Phys. Rev. C (1987) 1435 13. H. Bando, T. Motoba, M. Sotona and J. Zofka, Phys. Rev. C, in press. 14. T. Fukuda, H. Ejiri, T. Shibata, H. Bando and T. Motoba. Proc. of 1986 INS Int. Symp. on Hypemuclear Physics, Tokyo (1986) p.l70.(ed. H. Bando, O. Hashimoto and K. Ogawa). 15. O. Hashimoto et al., Nuovo Cimento 102(1989) 679. 16. S. Aoki et al., Proc. of the 17th INS Int. Symp. on Nuclear Physics at Intermediate Energy, Tokyo (1988) p. 13. (ed. T. Tukuda and T. Nagae, World Scientific, Singapore, 1989). 17. K. Imai, Proc. of TRIUMF/KEK Workshop on Hypernuclear Physics at KAON, Tsukuba (1989) p. 163.(ed. K. Nakai). 18. T. Fukuda, ibid p. 175. 19. See, for example, Proc. of the 17th INS Int. Symp. on Nuclear Physics at Intermediate Energy, Tokyo (1988). -88- —1 1 . . . . 1 ...,,... . (a) Present 800 > c •—3 -5 2 600 y vi,« • 3 400 a (J O 200 ' (bj DWIA f > .. i .... i /• l-.--.-m l~_ m 260 270 280 290 2 MHY-MA(MeV) 250 260 270 280 MHy-MA(MeV) Fig. 1. 4He (stopped K-.ir*) spectra observed by Hayano et ai., which reveal presence of a bound state of ^He with 1=1/2 and S=0 Or clu^iel only). 10000 fH -• 4He TT" 1500 (Pa/2 . P) 8000 (CH)n ( Stopped K", TT" ) 13, dW \'llllllt, ! iVlHit 1000 w,"H, . ir 6000 1 i K- p -» E+ ff" • ', | (Pa/2" . S) a 500 4000 3 o V, o v, '<%.,•. ,"",,"".«„H'^ XH. 2000 M*l',» ""•V. _i_ 150 200 250 300 7T~ Momentum (MeV/c) Fig. 2. re" spectrum from 12C(stopped K", 7t") reaction. -89- TDF 300 MeV/c Iron mzmmmmmmm>mmmMmm mmmmmmzmzm Fig. 3. Layout of the superconducting TOROIDAL spectrometer. 89 Y 3F. "CM C 150 -o V' 100 " - "<£ r~'ot i4 X 50 (Th .•rv..*.^ -30 J-20 -10, , -BA(MeV) 89, + + Fig. 4. The (rc , K ) spectra for AY. -90- AEROGEL CERENKOV LUCITE \ CERENKOV 800 MeV/c 700 MeV/c 600 MeV/c p;g 5_ Layout of the Superconducting Kaon Spectrometer. Fi -91- Weak Decay of A Hypernuclei Department of Physics, Faculty of Science Osaka University, Toyonaka, Osaka, 560, JAPAN Tadafumi Kishimoto Abstract: Hadronic (mesonic and nonmesonic) weak decay of A hypemuclei is discussed. Lifetime of medium heavy hypernuclei is determined primarily by the nonmesonic decay. It is discussed that experimental study of branching ratio and angular distribution of decay particles are important to elucidate the nonmesonic decay mechanism. Possibility is pointed out that mesonic decay could be used to search for hypothetical H particle. §1. Weak decay modes of A hypernuclei 1-A. Mesonic and nonmesonic decay of A hypernuclei A particle has mesonic-decay mode as A -+ p a- + 38 MeV 1-A n 7T° + 41 MeV, 1-B which also occurs in a hypernucleus. Other minor leptonic decay modes, which is interesting and accessible in a future high intensity facility, are not discussed here. When A particle is embedded in a nucleus, additional nonmesonic decay is possible. A + p -* n p + 176 MeV 2-A A + n -+ nn + 176 MeV 2-B The decay rate of hypernuclei is given by competition of the two decay modes. A nucleon produced by the mesonic decay (eq. 1) has to be in a nuclear state. Since momentum transfer of the mesonic decay (~ 100 MeV/c) is smaller than that of the Fermi momentum (~ 250 MeV/c) of a nucleon in a nucleus, the state is occupied in most of cases by another nucleon (Pauli blocking). Thus the mesonic -92- decay is generally hindered in medium and heavy hypemuclei. Since detailed discussion of the mesonic decay is given elsewhere \ no further discussion on the decay is made here. The nonmesonic decay (eq. 2), on the other hand, has a large momentum transfer (~ 400 MeV/c) so that the Pauli blocking effect is negligible. Conse quently the nonmesonic decay dominates the weak decay of medium and heavy hypernuclei. Mechanism of the nonmesonic decay is not well known because we have little experimental information on the decay. Thus only brief consideration given in the following can been made 2. Since momentum transfer of the decay is large, it is reasonable to assume that initial A and nucleon are in relative s-wave. The decay amplitude is classified by its spin isospin of the initial and final state as shown in table 1. Initial Final Matrix Rate Isospin Parity state state Element change l 'So S0 a a* 1 no 3Po b2 1 yes 2 3Si c 0 no 3A d2 0 no 2 #e(«ri-cra)g e 0 yes 2 3Pi f 1 yes Table 1 Amplitude that can contribute to the nop mesonic decay of A hypernuclei. The initial AN system is assumed to be relative s-wave. This classification is valid for s-shell hypernuclei. Since we have little experimental information to nail down relative importance of each amplitudes, it is assumed (not proved experimentally) that AJ = 1/2 rule hold in the nonmesonic decay. The rule gives the relation between amplitudes of proton-stimulated and neutron-stimulated decay as {flni K, /n} = V^{ap, bp, fp}, where subscripts represent either proton-stimulated (eq. 2-A) or neutron- stimu lated decay (eq. 2-B). Analysis of nonmesonic decays of ^He and AH shows that the amplitude f dom inates in the nonmesonic decay 2. If that is the case, 0.5 is predicted as the ratio of (rp/r„) for 1=0 hypernuclei. Theoretical description of the nonmesonic decay can be given by one boson exchange. Since one pion exchange is of primarily importance, the nonmesonic decay has the structure similar to that of the nu cleon nucleon strong interaction in which 1=0 tensor force is important. Thus -93- it is reasonable that theories based on meson exchange predict dominance of 1=0 amplitudes in the decay. Experimental data shows large neutron stimulated decay (1=1 component) which contradicts the theoretical prediction. The large momen tum transfer of the nonmesonic decay suggests importance of the short range behaviour of the nonmesonic decay, equivalently introduction of heavy mesons. Addition of isovector type meson doesn't change much the isospin structure and thus the data suggest the importance of mesons which are not isovector type. From the experimental point of view, determination of the Tp and T„ is subject to change due to final state interaction. Energetic nucleons produced by the nonmesonic decay (eq. 2) have collisions with nucleons in a nucleus. The Tp and Tn may appear to be different because of such intra-nuclear cascade. Thus the intra-nuclear cascade process has to be studied to clarify the mechanism of the nonmesonic decay. Another interesting experimental information is the interference of amplitudes involved in the nonmesonic decay. We have an asymmetry of the decaying pions with respect to the polarization of the A due to parity violation of weak inter action. It has been pointed out that nonmesonic decay could have such angular distribution with respect to the polarization of A in hypernuclei 3. Study of the angular correlation requires polarized A hypernuclei. It has been shown that po larization of A hypernuclei can be produced effectively by the (x+, K+) reaction. The polarization is produced by the distortion of the pion and kaon waves 4 and polarization of elementary (ir+,K+) reaction s. An experiment to investigate the asymmetry angular distribution with respect to the polarization axis will be car ried out at KEK in which we hope to elucidate the nonmesonic decay mechanism 6. The The weak decay takes place mostly from the ground state of hypernuclei. However it has been shown that use of the cross section going to highly excited state in the (ir+,K+) reaction can increase drastically yield of the polarized A hypernuclei 7. Here I just would like to mention that (A'~,7r~) reaction can also be used to produce polarized hypernuclei. Figure 1 shows differential cross section as well as polarization of A in the (K~,ir~) reaction calculated from elementary amplitude given by phase shift analysis 8. It is seen that at around 1.0 and 1.5 GeV/c we have large elementary polarization. Beam intensity has to be considered additionally to see overall figure of merit. 1-B. AJ = 1/2 rule It is worthwhile to see the foundation of the AJ = 1/2 rule because we use the rule in the analysis of weak decay of hypernuclei without proof. The empirical AJ =s 1/2 rule is first formulated by Gell-Mann and Pais 9. The rule has been a -94- puzzle ever since. Experimentally it is known that a K3 decays almost three orders of magnitude faster than a K+. Since only A/ = 3/2 amplitude contributes to the K+ decay, the ratio is known to be evidence of the AI = 1/2 enhancement. Since the rule is not exact obviously, it has been believed that the rule has dynamical origin from interplay between strong and weak interaction. There have been several mechanisms proposed to explain the rule. One particular graph so-called "Penguin" diagram shown in figure 2 has a intriguing property that it represents the pure A J = 1/2 amplitude. In this case soft gluon exchange is quite important for the rule. Unfortunately since there has not been good way to describe the soft QCD except possibly lattice QCD calculations, derivation of the rule from the basic principle is a little beyond the reach of the present theory. Since the rule might be related to the hadron structure, it doesn't seem to be obvious that the rule holds in nuclei where there might be some change in hadron structure. If the soft gluon exchange is responsible for the rule as suggested by "Penguin" diagram, pionic decay which would occur in the surface region of a baryon might be different in nuclei. Thus it should be tested experimentally that the rule holds also in hypernuclei. For the mesonic decay it is relatively easy to see the validity of the rule. It is simply given by the branching ratio of ir~ and ir° decay. However almost no test has been made on the validity of the rule in hypernuclei. For the nonmesonic decay it is not straightforward to see the rule unfortunately. Detailed systematic study of light hypernuclei with variety of spin and isospin will disclose the validity of the rule. §2. H particle formation from A hypernuclei The weak decay of A hypernuclei might produce the H particle if there exists light H particle. The H has been the only dibaryon candidate with S = —2 to be lighter than AA, since it was originally predicted as the lightest six-quark state based upon the MIT bag model 10. Thus it could be a particle that can decay only by weak interaction or is completely stable. In spite of much theoretical effort to calculate properties of the H, no experiment has so far given any definite conclusion on the existence of the H. Recently, an interesting prediction is made on the H mass by the the lattice QCD calculation which is believed to manifest QCD at low energy. The calcula tion, with the largest lattice ever used for the H, shows that the mass could be quite light, even lighter than that of two nucleons u. If that is the case, the H becomes completely stable. -95- The interesting possibility then arises that A hypernuclei could produce the H by AS = -1 weak decay u. E the H is as light as two nucleons, additional hadronic decays are possible to produce the H which are mesonic (MH) and nonmesonic (NH) decays given as, A + p-t H + 7T+ 3-A A + n-* H + TT0 3-B A + n + N -f H + N. 4 The NH decay (eq. 4) needs another nucleon or nucleus to satisfy energy momen tum conservation. We focus our discussion on the MH decay (eq. 3), because the NH decay is difficult to detect experimentally. Since the ir+ in the MH decay is not produced in the mesonic decay of A hypernuclei, it thus can be a unique signature of the H production. The lowest order process of the MH decay is shown in figure 3. The H is produced by the pionic decay of the A followed by EN fusion into the H through the vertex T in hypernuclei (process I). There is another graph where AA fuse into the H (process II). The amplitude of process I is given as follows 12, 5 M - {2EH2MHN2ER) J — (2E/,2ES)^ ' where PA = (P~A,EA) represents the four-momentum of any particle A. Normal ization and conventions are taken to be the same as ref. 12. The weak decay invariant amplitude Tw is taken from the experiment; TW{K —* H?r) is replaced by the TW(E —»• A^) which is given by the 5 lifetime. V is an internal wave function of a A hypernucleus. T, which represents fusion of two baryons into the H, has been given by assuming Gaussian wave functions of those quarks as 13 2 T(Pp - P=) = To I —J exp ( -—(pp - ps) J , 6 where R is taken to be 0.83 fm according to ref. 12. F0 is the color-spin flavour recoupling coefficient that is given by the Q3 ® Qz decomposition of the H particle as 12'13 Iff >= /||8 ® 8 > +\f^£N >,=o -^|AA > +^I|EE >« . 7 Note that the wave function has a large (80 %) two color-octet component which may be irrelevant to describe the physically meaningful decomposition1S. However -96- we include this to give rather conservative estimate. In order to obtain the MH- decay rate, the spin and isospin projection operator has to be included to extract the relevant spin and isospin component. In the following are shown numerical results for the MH decay from j^3C, \Ee and ^He. For the internal wave function ij>, we assume nucleons and A are moving independently with the proper momentum distribution. The wave function of nucleons is taken to be a Fermi-Gas type for 12C and Gaussian for 4He and 3He, respectively with momentum distributions given by (e,e'p) reactions 16. The wave function of A is obtained by assuming a square well potential. Its radius is taken to be the same as a charge radius 17 and the depth is adjusted to reproduce the binding energy. For convenience of the numerical calculation, the A wave function so obtained is replaced by the Gaussian one that has the same average momentum. The residual nucleus is assumed to be in its ground state for ^He and \Ke. Excitation of an s-hole state in the residual nucleus is included for \3C. One third of the residual 10B nuclei are assumed to be excited by 20 MeV. Figure 4 shows the MH-decay rate to produce TT+ as a function of the H mass calculated for process I for the three A hypemuclei. The process II has to be added in amplitude to give the actual MH-decay rate, for which purpose we need the relative phase of the two amplitudes. Unfortunately no experiment can give the relative phase; we thus show two cases in figure 4. One uses a relative phase obtained by assuming SU(3) 18 symmetry for hadronic decay of octet baryons and the other uses a phase 180° rotated from it, which is referred as anti-SU(3). The obtained MH-decay rate is roughly 10-2 ~ 10-3 of that of free A decay when the H mass is below 18S0 MeV. Since A hypernuclei are known to have comparable lifetimes as that of the free A, the value can also be taken to be its branching ratio. The MH-decay rate depends on mass number of hypernuclei, almost the same as the nonmesonic decay. Since the H in the final state is not subject to the Pauli- blocking effect, no suppression is expected at any momentum transfer. Eq. 2 suggests that nonmesonic-decay rate is linear to mass number of hypemuclei, and this has been observed to hold up to \2C 19. We can expect the same for the MH- decay rate from eq. 3. Pions from the mesonic decay, which can be backgrounds through final state interaction (FSI), are suppressed in heavy hypemuclei. Thus use of heavy hypernuclei helps to improve signal to noise ratio for the H produc tion. However once the nonmesonic decay is dominant, there is no reason to go heavier hypemuclei. Since an increase of the MH-decay rate means an increase of the nonmesonic-decay rate and consequently the branching ratio of the MH decay doesn't increase. The maximum H mass (MMAX) to be searched for by the TT+ MH decay can be expressed in term of binding energy (BE) as follows, -97- MMAX =mf + mA.- BEP - BE/, - m, 8-A = -BEP - BE^+ 1914.3 MeV. 8-B Since light hypernuclei have small binding energies, it is more convenient to search for heavy H (MH > 2MN). For instance, the MH-decay rate of ^He (•MAMJC=1906.4 MeV) doesn't decrease much compared to ^He (MMAX=1891A MeV) and fC (MMAX=18S7.1 MeV) as shown in figure 4. If the H mass is light, heavy hypernuclei is useful to search for the H because of large MH-decay rate. The present calculation has to be taken as an order of magnitude estimate. The calculation is rather conservative; thus it is highly probable that one can detect energetic ir+ in the weak decay of A hypernuclei if a strongly bound H does exist. Recently several experiments have been proposed to search for the H 20. Since the experiments intend to look for a relatively heavy H, they require a high energy kaon beam (~ 2 GeV/c) with high intensity. However if one wishes to investigate the H around the two nucleon threshold region, the experiment proposed here gives good way to search for the H. Weak decay of A hypernuclei has been exper imentally studied. The branching ratio calculated here is almost within reach of these experiments. If the H is lighter than two nucleons, other type of search can be made. A nu cleus becomes unstable against (A5 = —2) weak decay leaving the H in the final state. Study of the stability of nuclei excluded possibility of the H particle a few MeV lighter than two nucleons. For such case the search for the H just around two nucleon threshold by the method proposed here is particular interesting, because it has been pointed out that high energy muons from the direction of the Cygnus X-3 may be associated with the H 21 and this is possible only when the mass of the H is very close to that of two nucleons 22. Since nuclear double weak decay cannot study this mass region, the method proposed here is the best to explore such possibility. §3. Lifetime of the heavy A hypernuclei Since mesonic decay is suppressed strongly for heavy hypernuclei, lifetime of the medium heavy hypernuclei is primarily determined by the nonmesonic decay. Eq. 2 suggests that the nonmesonic decay rate is proportional to number of nucleons that can participate to the nonmesonic decay. Nonmesonic-decay rate divided by number of nucleons in a hypernucleus looks almost constant at least up to A C which support the consideration 18. However, overlap of A with nucleons does not increase at some point that fact means there is saturation of the nomnesonic- -98- decay rate. Actually the lifetime of the ^U shows such saturation ", although the interpretation of the data is not definite yet. It has been pointed out that the Cabibbo angle may vanish under strong mag netic field obtainable in a nucleus 23. In that case decay rates of hypernucleus would decrease drastically. In order to see such effect, lifetime of hypernuclei as a function of the mass number as well as spin of hypernuclei is necessary. We have quite limited information on lifetimes of medium heavy hypernuclei and actually no information on the lifetime as a function of spin of hypernuclei. In heavy hy pernuclei there may be lots of isomeric high spin states. However it is not easy to specify the spin of the hypemuclei where weak decay takes place. If we can acquire much spectroscopic information of heavy hypernuclei, we could have some methods to measure the lifetime as a function of mass as well as spin. As an example let us consider the level structure of rotational levels of rare-earth hypernuclei. It is reasonable to assume that nuclear collectivity is not affected much by the introduction of A particle in a nucleus. Figure 5 shows level scheme of rotational162 Dy nucleus and level scheme expected for ^Dy. 162Dy is taken just for example. Spin nonzero nuclear levels split into two levels because of parallel or anti-parallel coupling of A spin to core spin. Since the splitting known in light hypernuclei is small, it is expected to be negligible for heavy hypernuclei. The transition rate of rotational levels is affected little by introduction of a A in a nucleus, thus the lifetime of each level would be the same as that of normal nucleus. The halflife of the 4+ state of le2Dy is 0.13 nsec which is close to that of free A particle. Measurement of the ratio of 7-ray yields can determine the weak- decay rate with quite large dynamic range as shown in figure 6. This method clearly specify the state where weak decay occurs. These rotational levels, which are lowest energy levels for given spin, are populated strongly by reactions that introduces large angular momentum and excitation energy into a nucleus. We may be able to find variety of states to measure the lifetime of hypernuclei once the spectroscopic study of hypemuclei gets progress. Reference 1) For example: H. Bando, paper in this volume 2) R. H. Dalitz and M. M. Block, Phys. Rev. Lett., 11 (1963) 96 3) T. Kishimoto, Proc. of the workshop on Hypernuclear Physics, KEK, Nov 25-27 1982, KEK 83-6 (1983) 50 (in Japanese), T. Fukuda et al., Proc. of 1986 INS Int. Symp. on "Hypernuclear Physics" (1986) 170 -99- 4) H. Ejiri et al., Phys. Rev. C37 (1987) 1435 5) H. Bando et al. MPFU (1989) 6) H. Ejiri, T. Kishimoto and H. Noumi, Phys. Lett. B submitted (1989) H. Ejiri et al., KEK proposal E160 7) G. P. Gopal et al., Nucl. Phys. B119 (1977) 362 8) M. Gell-Mann an A. Pais, Proc. Glasgow Conf. 1954, 342, Pergamon London (1954) 9) R. L. Jaffe, Phys. Rev. Lett., 38, 195 (1977); 38, 1617 (E) (1977) 10) Y. Iwasaki, T. Yoshie, and Y. Tsuboi, Phys. Rev. Lett., Vol 60 (1988) 1371 11) T. Kishimoto, in Proc. of "1988 Internal Symposium on Hypernuclear and Low-Energy Kaon Physics", Padova, Italy, Sep. 1988, Nuovo Cimento "to be published" 12) A. T. M. Aerts and C. B. Dover, Phys Rev. D, Vol 28 (1983) 450; A. T. M. Aerts, and C. B. Dover, Phys. rev. D, 29 (1984) 433 13) R. P. Bickerstaff and B. G. Wyboume, J. Phys. G 7, 275 (1981); 7, 995(E) (1981) 14) The author is grateful to Profs. F. C. Khanna and K. Shimizu for discussions on the so-called hidden color component. 15) S. Frullani and J. Mougey, Advances in Nuclear Physics 14 (1984) 1 16) H. de Jager, CW. de Vries and C. de Vries, Atomic Data and Nuclear Data Tables, 14, (1974) 480 17) 0. E. Overseth, Rev. Mod. Phys. 52 (1980) S277 18) R. Grace et al, Phys. Rev. Lett. 55 (1855) 1055 J. Szymansky, PhD thesis Carnegie Melon Univ., unpublished 19) P. Bams et al, AGS proposal 814, K. Imal et al, KEK proposal 176 20) G. Baym, E. W. Kolb, L. McLerran, T. P. Walker and R. L. Jaffe, Phys. Lett. 160B (1985) 181 21) J. F. Donoghue, E. Golowich and B. R. Holstein, Phys. Lett. 174B (1986); ibid Phys. Rev. D34 (1986) 3434 22) J. P. Bocquet et al., Phys. Rev. Lett. B 192 (1987) 312 23) A. Salam and J. Strathdee, Nature Vol. 252 (1974) 569 -100- ' I— 'I • ' I • • I ,••••!• — «r-r r n 5 - n(K" ,TT")A \ a 4 r a b -a < 1 1 1 1 1 1 1 1 K n(K" ,TT-)A /7--.. 0.5 o 0.0 cd N •i—( "3 -0-5 \\ /I -1.0 < 1 1 1—I 1- v. V J3 2.5 n(K" ,7T~)A a) 2.0 b -a CM 1.0 " OH 0.5 - \ 0.0 -I. . -*•*<.'••' . | , , ,££ |—,—,—C 500 1000 1500 PK (MeV/c) Figure 1 The differential cross section (top), polarization (middle) and figure of merit (bottom) of the n(K~,ir~)A reaction are shown as a function of incident kaon momentum. Solid, dotted and dashed lines correspond to laboratory angles of 0, 8 and 16 degrees, respectively. -101- u,c, t u,c, t u, d o,d Figure 2 The penguin diagram. H A-2N Figure 3 The lowest order process of the H production is shown graphically. Here mesonic decay of A followed by H~p fusion into the H is referred as process I. Another similar process (process II), in which AA fuse into the H, is indicated in parentheses (see text). — 102 — Decay rate v.s. H mass i | i~ 1" I I '| I I I I |'™l™l l~l"|'"l I I I n i i r 1.00 fr? 0.50 < 0.10 0.05 h 1820 1830 1840 1850 1860 1870 1880 MH (MeV) Figure 4 Decay rates as a function of the H mass are shown. Hypernuclei studied here are "C, ^He and ^He. Solid lines correspond to the decay rate with only process I. Vertical line shows effect of interference on the PH-decay rate of l3C between pro cess I and II. The lowest value of the solid line is obtained by SU(3) prediction for the relative phase and the phase due to anti-SU(3) gives the highest one (see text). -103- 6+ rje-4) + U4) 4 "X TJ4-2) 2+ 0+ 1'62T 163 Dy -ADy Figure 5 Level scheme of low-lying 162Dy is shown (left). The sequence of rotational lev els is clearly seen. The expected }?3Dy level scheme is shown (right). The figure shows that branching ratio of decay of the 4+ state (either |+ or |+) can give the weak decay rate of the 4+ state. 10 -8 o -9 w 10 E • t—i "a) 10 -10 10 -11 0.2 0.4 0.6 0.8 1 Br I7(4-2*6-4)/l7(6-4) Figure 6 Partial lifetime of weak decay of the hypemuclear 4+ state is shown as a function of intensity ratio of 7 rays. — 104 — Pion-induced Double Charge Exchange Reactions for studying a Soft Giant Dipole Resonance of Light Neutron-dripline Nuclei T. Kobayashi (KEK) [1] Introduction This talk has no direct relation to many experiments, such as the hyper nuclear physics or the rare decays, which are being discussed for the kaon factory. But I think it is one good example belonging to conventional nuclear physics, for which kaon factory can contribute. The talk is intended to be a short one on a very specific subject: a soft El mode of the neutron-dripline nuclei. [2] Soft Giant Dipole Resonance The story started from the imagination of K. Ikeda<1:>. Fig. 1: Schematic picture of two kinds or isoveclor dipole oscillation, protons (shaded area) against neutrons (white area), in the neutron-rich nucleus with neutron halo. "normal" mode Excitation Energy His idea was that a giant dipole resonance(GDR ) of extremely neutron-rich nuclei with a neutron halo could split into two components, as shown in Fig. 1. One component would correspond to the — 105 — oscillation of core protons against core neutrons with a normal frequency, and the other to the oscillation of the core against halo neutrons. Since the restoring force of the oscillation is roughly proportional to the derivative of the density distribution, the frequency of the latter mode is expected to be very low. Therefore there is a possibility that additional "soft" GDR may be observed in a neutron-rich nucleus if it has a neutron halo. [3] Nucleus with a neutron halo ? As far as we know, the nucleus J1Li, the heaviest Li isotope, is one of the best candidates to look for the soft GDR, since several observations on ^Li suggested the existence of a neutron halo around the 'Li core : (1) The small two-neutron-separation energy : S2n = 0.19 ± 0.11 MeV. (2) The large nuclear matter radius <1> [Fig.2]: R^ = 3.27 + 0.24 fm. (3) The narrow momentum distribution of 9Li fragments produced through the projectile fragmentation of' JLi at 0.8 GeV/nucleon [Hg-3]<3> 1 • ^ • He o U - Be - a B - 1 • f * V i j • / I X5 ! 2.0 1 1 5 10 15 -200 -100 0 100 200 Is eutron Num >er Pi [MeV/c] Fig. 2: Nuclear RMS radii Fig. 3: Momenlum distribution of "Li from * *Li The most naive interpretation of these observations is that the 11Li nucleus consists of a 9Li core ( Rms <= 2.4 fm) and a neutron distribution extending up to = 8.2 fm. -106 — [4] Giant Dipole Resonance of 11Li ? Historically, the GDR was discovered by photonuclear reactions. Recent development of secondary nuclear beams at— 1 GeV/nucleon also enables us to study the photonuclear cross sections of any p-unstable nuclei. This was done by shooting the *l Li projectile on high-Z targets <3>. This reaction is, following the Weizsacker-Williams (W-W) method, equivalent to the interaction of the projectile with virtual photons (Ey 5 40 MeV) generated from the target Plotted in Fig. 4 are the electromagnetic dissociation (EMD) cross sections of the ' 'Li projectile. The cross sections are compared with those for the (12C+Pb) case as an example for stable nuclei. If the EMD cross sections of' *Li and 12C projectile are compared after scaling the cross section by Zproj.2.* 'Li h°s about 80 times the cross section of 12C. Following the W-W method, the EMD cross sections can be related to the energy of the GDR. Estimated energy of the soft GDR turned out to be 0.9±0.5 MeV, which is really small compared with the systematics of the GDR. o.uu . ' ' "1 1 1 r—i—i i i T- . Fig. 4: Target charge dependence of the , a\*° I- EMD part of the interaction cross section °.*r°_ 1.00 r~ (closed square) and the y two-nculron-removal cross section (open .•' Ay O.SO : i •'• .-•'• '• square) for a 1 lLi projectile at 0.8 GeV/A. y y w / • T/ " y / 0.10 — Ai —: : n IIK .. ..i • • • • • 11. I 10 SO Target. Prolon Number [5] Two models supporting the soft GDR This interpretation is consistent with a simple cluster model <4>5>, where J1Li is treated as composed of weakly-coupled clusters of two-neutrons and the 9Li core. This model predicted, same as the case of deuteron photo-disintegration, that the nLi has a very soft El mode at twice the two-neutron separation energy; about 0.4±0.2 MeV. Recently, a shell model calculation*6* was performed taking into account the weak-binding of the last two neutrons. The calculation also showed that El strength is distributed below 1 MeV excitation energy. — 107 — [6] Soft E1 mode of the neutron-rich nuclei ? Those experimental facts and theoretical considerations suggest that the ''Li has a very soft GDR at a low excitation energy; 0.4 - 0.9 MeV. This soft mode can be interpreted as the oscillation of the core (9Li in a R=2.4 fm sphere) against the halo neutrons (2 neutrons in a R=8.2 fm sphere). This kind of phenomena has never been observed for nuclei near the valley of stability. However, the experimental observables on the soft GDR were so far indirect. It will be very interesting to study the excited states of the neutron-rich nuclei, including the soft El mode, by other methods. [7] Application of double charge exchange (DCX) reaction, and short summary One possibility is to produce the ground and excited states of 1!Li via the pion-induced DCX reactions, such as 11B(7t-,7i+)11Li. This experiment requires high intensity beam and high energy resolution (~ 0.3 MeV FWHM), due to the expected small cross sections and the necessity to resolve discrete nuclear transitions. As an example of such experiment at the present meson factories ( EPICS at LAMPF), yield is estimated to be only 40 counts /day, assuming beam of 5xl07 n" /sec at 200 MeV on 0.5 g/cm2 target with 10 msr solid angle and do/d£2=50 nb/sr. This tells that experiment itself is possible using existing facilities. However, the yield itself is too low for spectroscopic applications: limiting factor of the experiment is still beam intensity and/or running time. In this context, the kaon factory, whose main objective is, I think, for the elementary particle physics or intermediate-energy nuclear physics, will also be able to help very conventional nuclear physics, due to its higher secondary beam intensity. [8] References 1.1. Tanihata et al., Phys. Lett. 206B (1988) 592. 2. T. Kobayashi et al., Phys. Rev. Lett. 60 (1988) 2599. 3. T. Kobayashi et al., Phys. Lett. B (1989), in press. 4. P.G. Hansen and B. Johnson, Europhysics Lett. 4 (1987) 409. 5. C. Bertulani and G. Baur, Nucl. Phys. A480 (1988) 615. 6. T. Hoshino, private communication. -108 — SEARCH FOR DOUBLE HYPERNUCLEI AND H-DIBARYON Kenichi Imai Department of Physics, Kyoto University (For El 76 collaboration) Abstract The search for double hypemuclei and H-dibaryon(H) by the hybrid emulsion method has been done at KEK. The experiment and its preliminary results are described. Future programs on this subject at BNL and KAON are quite interesting. Among all combinations of the 6-quarks (u,d,s), the QCD color magnetic interaction becomes most attractive for the H (I=J=0, ssuudd) and so the H is the lowest state among all 6-quark states1. It is very important to search for H in order to study multiquark system and QCD. On the other hand, there have been two emulsion data which claimed the existence of double hypemuclei2. It is argued that the existence of such a weakly decaying double hupemucleus can exclude the H in the mass region of 1900 - 2200 MeV3. So it is very important to confirm the existence of double hypemuclei. The emulsion is the only detector which has enough resolution to detect very short tracks of hyperfragment. The hybrid emulsion technique is much more advanced than the old emulsion measurement in the sense of statistics and reliability of the data. In this experiment, the (K*,K+) reaction from a nucleus in the emulsion is identified by counters. Then the strangeness of -2 is transfered to the target nucleus. In most cases, (K",K+) reaction proceeds through one step process like — 109- K"p - K+H in the nucleus. Since the E" has large momentum (>500MeV/c) than the nuclear Fermi momentum, a large fraction of the (K",K+) reaction from a nucleus is expected to be a quasi-free process and E" is scattered out of the nucleus. Actually, in the heavy liquid bubble chamber experiment with 2.1 GeV/c K" beam, E" was observed in 50 % of the identified (K",K+) events. Most of the produced 3" decays in flight but in the present experiment 10 - 20 % of S" are expected to stop in the emulsion. Then the stopped E" is absorbed by a nucleus and produces an excited nuclear state with s=-2. The conversion process E"p -> AA can take place in the nucleus and if two A are trapped by the nucleus it is a double hypemucleus. Because of the Q-value (28 MeV) of the conversion process, a light hyperfragment can be emitted and observed as a short track with decay vertex. If a light hyperfragment of s=-2 (double hypernucleus) is emitted, it should be identified by its sequential weak decay. If H exists and its mass is less than the mass of two A, the excited nuclear states with s=-2 could be cooled down by emitting the H by the strong interaction rather than end up with a weakly decaying double hypemucleus. If H decays into 2"p near the stop point of E" (widiin 1 mm), H can be clearly identified in the emulsion. It is possible if the life time is about same or less than that of hyperon. When the 3" is absorbed by a deuteron, the branching ratio of the H emittion was estimated. It is proportional to the mass of the H and about 10 % at 2150 MeV. The branching ratio of H -> 2T~p decay was also estimated and about 50%. The set up of the experiment is shown in Hg.l. The separated K" beam of 1.6 GeV/c is focused onto the emulsion target. The K7it" ratio is as high as 1/3 at the intensity of 3 x 103 K'/spill. The good K/it ratio is important especially for the emulsion experiment. The incident K" is clearly identified by an aerogel Cerenkov counter (AC1) and TOF measurement The scattered K+ are -no- detected widi a K+ spectrometer which consists of a magnet (0.7 Tm), wire chambers (PC1-3, DC1,2), an aerogel Cerenkov counter (AC2) and TOF counters. The spectrometer has large acceptance (0.15 str) and moderate momentum resolution (Ap/p = 3.5% at p=l .6 GeV/c). Redunduncy of the tracking chamber is quite necessary to kill the K"-decay event in the spectrometer. The particle identification is done by using me Cerenkov counter and TOF measurement. The index of AC1 is 1.04 and its pion detection (rejection) efficiency is 99.3% . The index of AC2 is 1.055 and its detection efficiency for 1.0 GeV/c pion is 98.7%. The TOF hodoscope is located at 2.7 m downstream from the target and consists of 14 counters. The size of each counter is 110x12x3 cm and it has H1949 photo tubes on both ends. The TOF resolution was measured to be about 80 psec(rms), which is quite satisfactory. A thin scintillator hodoscope (CT) is placed at the entrance of the magnet to form the matrix coincidence with the TOF hodoscope to identify the charge of the scattered particle for the trigger logic. Thus die trigger requirments are ; an incident particle is K" and charge of a scattered particle is positive. The typical trigger rate was about 40 events/spill. A mass spectre of the scattered particle is shown in Fig.2. The K+ is clearly separated even wiuiout using AC2 information to reject pions. In order to identify the (K",K+) vertex and follow down the 3~ track to its stop position, K+ track should be identified in die last emulsion sheet. To do this, the emulsion stack is sandwitched with silicon microstrip detectors (SSD1-4). This is the key detector to connect the counter information and the emulsion tracks. The dimension of the SSD is 50x50 mm in area and 0.3 mm thick. A strip pitch is 42|im and me every third strip is read out by ADCs. The charge division method is employed to get good position resolution. The position resolution was measured to be 16uxn (rms) by using finer SSDs of which strip pitch is 15um. The result is shown in Fig.3. — Ill- The emulsion stack is vertical type and each stack consists of 43 layers of the emulsion sheet. The size of each sheet is 23x23 cm and its thickness is 1.07 mm including 70 urn thick polystylene film base. The stack is mounted on the high precision movable table which is controlled by a micro-computer to get the uniform irradiation at the particle density of 6xl05 particle/cm2. To help to find the K+ track at high particle density, the last emulsion sheet (called changeable sheet), which is most important to locate the K+ track, is changed 10 times for each emulsion stack exposure. So the particle density at the changeable sheet is 6xl04 particle/cm2 and it is easier to find the track predicted by the silicon microstrip detector and wire chambers. Between the emulsion sheets, the connection of tracks is possible at high particle density because of the better position resolution of me emulsion. All the emulsion stacks have been already exposed and one of them was developed and scanned to check the connection between the counter data and emulsion tracks. The predicted position of the tracks given by the analysis of the counter data were searched in the emulsion. So far we could locate most of the events in the emulsion. We have located 43 (K",K+) events of PjH- >0.9 GeV/c. Among mem we found 23 E~ candidates, and 4 stopped S". We have 15 emulsion stacks (30 liters in total volume) exposed to the beam. According to die preliminary off-line analysis, 5000 ( K",K+) events will be identified by the counter system and more than hundreds of stopped 2" should be observed in the emulsion. This is about hundred times better statistics than before. So we expect to obtain some new informations about H, double hypernuclei and s=-2 nuclear states. The trigger requirement allows us to take (K~,jt+) events simultaneously. The number of the events is 10 times more than die (K",K+) events. Further analysis is now in progress. The experiment to search for H is now in preparation at BNlA The new -112 — kaon beam line is now under construction for this experiment which needs high intensity beam of good K/TC ratio. The design value of the beam intensity is 106 KVspill at 2 GeV/c with the K/rc ratio of 1/1. The H is searched by the following reaction; K" + 3He-K+ + n + H (1) K-+P-K+ + E", S' + d-n + H. (2) In die reaction (1), K+ and neutron are detected to identify the H-production. In the latter case, die E" which is produced by (K",K+) reaction is stopped in the liquid deuterium target. By measuring the neutron energy, one can identify die H-production. In bodi cases, me model caluculation of die H production was made5 and die experiment is expected to provide a conclusion about die existence of die H. Before die KAON is ready, we will have a conclusion in any way. If double hypemuciei are established, die spectroscopy of s=-2 nuclei can be done widi high resolution spectrometer as die second generation experiment of hyper nuclear spectroscopy. If die H is found, by using a lot of H, various decay modes of die H and even H-nucIeus interaction can be studied at KAON. One of die interesting subject is die size of die H which can be measured by attenuation meuiod. One of die natural extension of E176-type experiment at KAON is to study s=-3 nuclear (or quark) matter by stop Q" experiment. The Q" is produced by, for example, (K",K+K°) reaction from nuclei. In the case of quasifree process, the momentum of Or is too large to stop in die emulsion. Only hope is die degradiation of £2" in die target nucleus. It can be estimated from die momentum spectrum of ~ from emulsion target in die present hybrid emulsion experiment at KEK. -113- References 1. RJaffe, Phys. Rev. Lett. 38, (1977) 195,617. 2. M.Danysz et al., Nucl. Phys. 49. (1963) 121 and P. Prowse, Phys. Rev. Lett, 12 (1966) 782. 3. B.Kerbikov, Sov.J.Nucl. Phys. 22(1984) 516. 4. P.Barnes, GJFranklin, Proposals of E813 andE836 to BNL. 5. A.T.M.Aerts and C.B.Dover, Phys. Rev. D2£ (1983) 450 and D2£ (1984) 433. liiimmasnrt ——AC2 pc2 —. . i ^.Charge Trigger Hodo-Scope (Upstream) Fig.l The schematic view of the experimental set up -114- MOMENTUM VS MASS Fig.2 Mass spectrum of the detected particles without aerogel Cerenkov information. Fig.3 Position resolution of the silicon microstrip detector -115- Physics with Polarized Hyperons and Low Energy Anti-Protons at KAON Factory ' Akira Masaike Department of Physics, Kyoto University Kyoto, Japan The polarized hyperons and low energy anti-protons will be quite powerful tools for experiments on the particle and nuclear physics using "KAON Factory". Very little is yet known about spin dependent interactions of strange particles, since there is no strange particle beam with high intensity. In the first half of this report some interesting spin related topics with kaon beams and hyperon beams are shown. Especially, new field concerning polarized hyperons and hypernuclei are presented. Also shown are ideas to. obtain polarized hyperons and polarized hypernuclei. In the last half of the report, we demonstrate the importance of medium., low and ultra-low energy anti-protons for the fundamental physics. The possibility for getting *) Talk given at Workshop on Intensity Frontier Physics (Japan/Canada) at KEK, April 1989. — 116 — anti-proton beam with higher intensity than LEAR are discussed. Such a beam can give answers to many fundamental but still unsolved questions on elementary particle physics at low energy. I. Spin Physics with Strangeness The strangeness is one of the important probes to understand the fundamental properties of hadrons. Some of the decay modes of hyperons offer opportunities to search for new phenomena. Especially, studies of spin dependent parameters involving hyperons will solve several problems of particle interactions. A couple of examples are shown below. § 1. Polarized Hyperons Spin dependence of hyperon interactions is interesting from following viewpoints a) Test of P and CP-violations b) Search for the existence of right-handed currents c) Test of Cabibbo's model d) Search for second-class currents Hyperon polarization in the production plane for finite angle of production or in any transvese direction for 0°-production is forbidden due to the parity conservation in the strong interaction. The helicity asymmetry of A production of the reaction K~+P+-»-A+ir at 9=0° with longitudinally polarized prcton is also negligible due to the -117- same reason. It would be very interesting to search for such forbidden polarization or asymmetry as an indication of the interference of the strong and the weak interaction processes. The parity violation effect on A-production at 6=0° can be compared to the p-p scattering and radiative capture reaction of slow neutron on heavy nuclei. The last one shows large helicity asymmetry at some p-wave resonances. P asymmetry coefficients ak (k=e, \> , and p) in A-*-pevg is different significantly from the value of | GJ/FJ| obtained from the electron-neutrino (e-\>) correlation coefficient o ^. The latter value agrees with the prediction of the Cabibbo model. T. Oka pointed out that the discrepancy can be 2) accounted for, if right-handed currents exist. However, it -118- is necessary to measure the spin asymmetry coefficients ct£p more precisely than previous experiments, in order to answer the problem. We can obtain polarized hyperon beams using polarized proton targets. It involves producing polarized hyperons from longitudinally polarized protons in the reaction K~+p,-<- T Y+TT as shown in Fig. 1. From conservation of angular momentum the hyperons produced along the beam direction must have the polarization of the target proton, as the Adiar's condition, which was used to determine the spin of hyperons. Since the target proton can be polarized more than 90%, very high polarization of hyperons will be obtained. In this case, the degree of hyperon polarization is known from target polarization and high intensity polarized beam is available covering wide energy range. §2. Spin Dependence of Hyperon-Nucleon Scattering The measurement of spin dependence of hyperon-nucleon scattering is interesting from the viewpoint of the spin-spin interaction of the hyperon-nucleon system. Furthermore, hyperon-nucleon resonances can be confirmed by spin dependent scattering of hyperons on the nucleon. There has been no experimental data on spin dependent parameters, except data on the P-parameter with poor statistics measured by a bubble chamber. For more precise measurements we can use the same method as mentioned above, — 119- in which hyperons have the same polarization as that of the target proton in the case of extremely forward angle production. Several two-spin-parameters as ACT (Yp) , Aff_(Yp), CLL(Yp), CNN(Yp) as well as three-spin-parameters can be measured using polarized hyperon beams and the second polarized target • (Fig. 2) . These experiments are similar ones which have been carried out on nucleon-nucleon scattering with polarized proton beams and polarized proton targets. §3. Strange Dibaryons There has been increasing interest in the strange dibaryons as multi-quark states. A significant peak has been observed in the missing mass spectrum of the reaction - - 2 K +d->-i: +MM at the mass of 2.13 GeV/c . Recent data at larger scattering angles show the second maximum at about 2.140 GeV which is of P-wave charactor and is encouraging for further study of S=-l dibaryon, although the nature of the 4) enhancement is still controversial. The nature of the peak can be studied using the polarized deuteron target. We can make partial wave analysis of the reaction K~+d,->-ir +A.p, if the spin parameters of the reaction would be measured (Fig. 3(a)). The decay distribution of Ap system concerning the initial spin direction gives us the information about the -120 — spin state of the dibaryon (Fig. 3(b)). In forward scattering of K~+d,-»-ir-+Ap , the Ap-system has the same spin component as that of the deuteron. Therefore, we can determine the spin state of the Ap-system and find out if there is a resonance. These methods can be also applied to search for dibaryons with S=-2. §4. Polarized Hypernuclei Spectroscopy of polarized hypernuclei is quite powerful for studying the hypernuclear structure. Polarized hypernuclei can be produced by using strangeness transfer reactions on polarized nuclei. The (K~,TT) reaction without momentum transfer (the recoil-less strangeness transfer reaction) has been used to produce hypernuclei. In this reaction the polarization of the target nucleus is also kept in the hypernucleus. Furthermore, the polarization of the target nucleon may be maintained as the polarization of the hyperon, provided that the polarized nucleon is changed to the hyperon. Polarized nuclear targets can be obtained by the dynamic method developed in KEK and other high energy laboratories. Recently, Li and Li nuclei in LiH were found to be polarized in 65KG' in a dilution refrigerator with free 19 14 13 radicals made by iradiation. F in CaF2# N in NH3 and C in organic materials are also able to be polarized dynamically. -121- The measurement of the asymmetry of the mesic and non-mesic decay of the polarized hyperons in hypernuclei is useful to clarify the weak process in nuclei and to know the mechanism of depolarization of hyperons in the nuclear matter. Angular distributions of y-rays from polarized hypernuclei are used for spin assignment for hypernuclear levels and multipole assignment for the y-transition. Possible polarized hypernuclei are given below. 6 i) K"+ Li+ * fLi*+ir~ In the case of recoil-less reaction, the configuration is considered to be (p^O (p-=-) . . >P - 7 7 * + li) K + Li, ->• (LI^+TT T A i Hypernuclei with polarized proton with the configuration of (Py)_ (P^n ^S^A can te Produceta- 7 7 iii) K"+ Li * He++ir° Here, A may be polarized, as a polarized proton in (p-=-) is transfered to polarized A. - 1J13 * 13 c* +ir - iv) K + C+ - A + Here, also A may be polarized. II Physics with Low Energy Anti-protons We discuss the physics potential of pp experiments over wide energy range of "p from meV to GeV. Possibilities of getting high intensity "p-beam using KAON-factory is mentioned. We believe that low energey "p-beam can solve many questions — 122- on particle physics. We have a hope to find phenomena beyond the standard model using anti-protons. The origin of CP-violation is one of the most important questions in particle physics and is crucial in testing the standard model. Furthermore, we don't know any phenomenon of T or CPT violation. We are much interested in the possibility of the existance of long or medium range "fifth forces" which look like gravity, but might have very different effects on matter and anti-matter. Another important question is "how we can understand the dynamics of confining gauge theories like QCD". Most of hadronic phenomena can be explained by naive quark models. But we should like to go beyond these models with the extra degrees of freedom expected from QCD. Some of the experiments, which might make progress on these questions, are shown below. § 1. CP-violation in p+p -»• A+A An example of a CP-test of the ~pp reaction is the •measurement of "5+a in p+p •+• A+A •*• "p+ir +p+ir~ . The polariza tions of A and A are equal and are perpendicular to the production plane. Here — 123- „ _ 2Re(s«p) where s and p are s and p wave amplitudes in A*ir~+p decay, respectively, a is the same parameter for p. We can measure the parameter A precisely as follows. A _ Np (up) -Np (down) +Np (up) -Np (down) Ntotal where N (up) and N (down) are the numbers of events with P P proton above and below the production plane. A = i P-(a+a) , where P is the A-polaxization. The value of a+a can be 6} calculated from several models. For example, it is -4 -0.8x10 in KM-model. In the case of multi-Higgs and -5 -5 left-right symmetry models it is -4x10 and -1.4x10 , respectively. Similar experiments of "- decay can be made by a pp facility. §2. Observation of Direct CP-VioIation A very clean signature of the direct CP-violation would be observed in the reactions "p+p -*• "K°+k +TT~ and "p+p •*• K°+K~+ir+ if we could observe a decay rate asymmetry between K° and lc°, to either ir+ir~ or ir0ir ° immediately after their production, as initial states at t=0 (K° or "K") can be -124 — + identified by tagging ^K" or •jr~K . r(K'-nr++ir-) _ I+4Ree, r(K">ir'»-Mra) _ .»-__, r(K°-fir0+Tr°) ~ l BKee However, only we can observe is the time dependent asymmetry after mixing of K°and K°. The experiment will be carried out at CERN-LEAR. But much more precise measurement can be done at KAON Factory. §3. Test of CPT-Invariance and Anti-matter The CPT theorem based on the quantum field theory is a relation between particles and anti-particles. It predicts the identity of mass, magnetic moment and width of particles and anti-particles, except for a reversal of the sign of the magnetic moment. No experimental evidence for violation of CPT has been found. The most sensitive test so far arises from the mass difference of K° and K°, that is; • J,11"?'. < 2.6X10"2 1% ~M sl The gravitational force on "p and its inertial mass is unknown and it is necessary to check them experimentally. In order to measure the gravitational force and inertial mass, — 125 — anti-protons must be deccelerated to ultra-low energy and stored in a Penning trap. They are then launched vertically 8) — up in a drift tube. It can be compared with the H ions. The energy loss of the particles rising lm is 10~ eV, which is very much small compared to the thermal energy. Such a low energy anti-proton might be able to be produced by a laser cooling method. No experiment has been done on the anti-hydrogen atom, molecule, or U-H atomic interaction potential. The feasibility study of H formation has been proposed by radiative capture of positrons by anti-proton in LEAR, even though the intensity of anti-proton is quite low. Production of the protonium is also interesting subject. §4. Heavy Quark Spectroscopy and QCD Much experimental information on the charmonium states comes from e e~ colliders. But the fact that only states PC — with J =1 have reasonable production rates, affects on the accuracy of the available data from such machines. On the _ PC other hand, in pp annihilation into 2 or 3 gluons all J combinations allowed for a fermion-antifermion system are available to form a resonant states. In such experiments excellent resolutions for mass and total width can be obtained. With high luminosity "pp-factory it would be possible to observe unknown states like Pj *=l+~), 3Dj(JPC=2 ), — 126 — D2 (J *=2 ) and nc- It is essential to measure their masses as it will provide valuable information about the spin-dependent forces in QCD. Accurate measurements of total widths for the narrow cc-states are important to check the predictions in perturbative QCD. The total widths of *p and *S, 2S, *D states are dominated by (cc) anihilation into two gluons, three gluons or quark-antiguark-gluon. Helicity amplitudes for creating each charmonium state can be studied by the measurement of decay angular distributions, which may give information on chiral symmetry violation in QCD. Precise measurements of photonic and hadronic transition are also interesting to clarify the multipole expansion for QCD radiation. Looking for new states in the decays of the (cc) states as glueballs, other QCD exotics, and neutral fundamental scalars is also important in "pp factory. Bottomoniums might be investigated with a "pp collider with beam momentum of 4.5V7 GeV/c, if the beam intensity of "p" 12 is more than 10 All the combinations of u, d, s, c, b quarks can be produced by charm and bottom factory using p" beams. §5. -Cooling and/or Storage of High Intensity Anti-proton Beam — 127 — The stacking of anti-protons can be done by stochastic momentum cooling. At CERN the anti-proton at around 3.5 GeV 1 2 are produced by an intense proton beam (^5x10 /sec) of 26 GeV/c. Anti-protns within a momentum bite of 1.5% and angular spread of up to 50 milliradians are collected and transported to the anti-proton accummulator (AA). In the AA they are stochastically cooled and stacked. The cooling rate in the AA is 2x10 /1.5sec with cooling emittances of 1.9ir mm-mradx2. lTrmm-mrad. Recently the cooling rate of anti-proton was improved by factor MO, using an additional cooling ring "ACOL". The cooling time const (t) is given by T=a=r, where W is the bandwidth, N is the number of anti-protons and a is a factor including noise limit, mixing limit and power limit. — 8 From the equation, T can be 10 N in the case of W=l GHZ and -128- provide pure stretched p-beam. The beam intensity of p at 4 8 14 GeV/c will be 4*10 per 10 protons with the momentum acceptance of Ap/p^0.02. A "p-p collider with momentum of 2^7 GeV/c with high luminosity could be a future option for the anti-proton factory. The problem of heating the "p production target may be serious. The target must be cooled efficiently and/or moved quite often. Intensive R and D are indispensable for getting such high intensity anti-proton beam. Fortunately, the expertise of beam cooling at INS and RCNP in Japan is in high level. I hope, it can be applied to this project. -129 — References 1) V.P. Alfimenkov et al.; Nucl. Phys. A398 (1983) 93. Y. Masuda et al.; Hyperfine Interactions 34_ (1987) 143. Y. Masuda et al.; Nucl. Phys. A478 (1988) 737c. 2) T. Oka; Phys. Rev. Lett. 5£ (1983) 1423. 3) A. Masaike; Proc. Third LAMPF II Workshop (1983) pl38. 4) H. Piekarz; Nucl. Phys. A463 (1987) 205c. 5) A. Masaike, H. Ejiri; Proc. Third LAMPF II Workshop (Fermilab, 1983) p823. S. Ishimoto et al.; KEK-preprint 89-22. 6) J.F. Donoghue; Proc. 1st Workshop Anti-matter Phys. at Low Energy (Fermilab, 1986) p242. 7) T. Morozumi; private communication. 8) M.V. Hynes et al.; Proc. 1st Workshop Anti-matter Phys. at Low Energy (Fermilab, 1986) p210. 9) R.L. Jaffe; ibid pi. -130 — Figure Captions 1. A schematic diagram of the production of polarized hyperons from the polarized proton target in Adair's condition. 2. Schematic view of the measurement of the spin dependent parameters of hyperon-nucleon scatterings, using polarized proton targets. 3. Search for strange dibaryons by polarized deuteron targets. a) (K , ir ) reactions from a deuteron target which is polarized perpendicular to the scattering plane. b) Production of a strange dibaryon from a longitudinally polarized deuteron target. -131 — 2,-, 2«+, A bear the target polarization K" 7T(0°) 2 or A Pol. Targ. Fig. 1 -132 — Backward or Forward Production of K"+ Pf Y + 7T yA K — "Pol.A T\ f3 ol.T.][ Poi.T.n yA K" A xi P p\ (Pol. and Unpol.) * K"+At —- Ai + TT° 1 ^- A* + Pi—A+ P 7T K' — 2 Pol.T. I Pol.T. H K"+P+ •27 + TT\ 1 -2* + Pr-^2 + P Fig. 2 -133- K (a) ". o^^ Pol. Deuteron (b) 7T"(0°) Pol AP•P Deuteron Fig. 3 -134 — PRECISE MEASUREMENT OF u+ POLARIZATION IN THE DECAY OF K+-*u.+ + v J. hnazato National Laboratory for High Energy Physics (KEK) Abstract An experiment to .measure the longitudinal polarization (Pn) of muons in the K|x2 decay with high precision is now running at KEK-PS as E195. A right- handed current is to be searched for as a deviation of £PM from -1.0. In order to improve statistical accuracy of the measurement, we employ a new method which uses the muons emitted from K+ stopped in a production target and transported through a specifically designed muon channel. The polarization is measured by means of conventional transverse-field |iSR technique. We are aiming at an experimental accuracy of 1.0 % for the determination of ^PM. 1. Introduction Search for a right-handed current (RHC) in weak processes is an interesting subject in particle and nuclear physics. A number of high precision measurements have recently been performed in leptonic and semileptonic processes [1,2,3]. Their results as well as non-leptonic cases [4] can be discussed in terms of left-right-symmetric (LRS) models [5]. In these models the apparent absence of RHC is attributed to the mass of me boson, WR, mediating an interaction of V+A type, which is much larger than that of the standard left-handed boson, WL. The effects of RHC are suppressed at least to the order of AKM(WL)/M(WR))2 • &1 general, the mass eigenstates, Wi and W2, are linear combinations of WR and WL. Therefore experimental limits from low energy leptonic and semileptonic processes give constraints on X and/or the mixing angle, £, provided the accompanied RH neutrino has a mass small enough. Thus experimental efforts to raise the limit are always important. One of the most stringent and model-independent limits on X, irrespective of the mixing angle, £, has been given by muon decay experiments of pion origin. At TRIUMF, measurements of ^PpS/p (where ^, 8 and p are the Michel parameters and Pn is the muon polarization in 71^2) were performed observing the positron endpoint spectrum [2]. A limit, ^P|j5/p > 0.9966 (90% C.L.), was obtained as a combined result of the longitudinal-field and the transverse-field method. This corresponds to a mass limit of M(W2) > 400 GeV. The integrated positron -135- asymmetry in the muon decay from n^2 has also been measured at SIN giving £PH.= -1.0027 ±0.0084 [3]. Similar polarization data for the strangeness changing counterpart, Kn.2, is, however, still in poor accuracy. Although an improved experiment was carried out at KEK-PS several years ago [6], its result gave only ^Pn, = -0.970 ± 0.047 (or /^P|i/> 0.902 (90 % C.L.)) while it should be exactly -1.0 if the interaction is purely left-handed. In the LRS model the deviation of PM from unity can be expressed as (for t, = 0 and assuming a light RH neutrino) 2 1 + Pju. = 2 *2 (sin9R/sin0L) , which is compared to the pion case, 1 + Pp. = 2 A,2 (COS6R/COS0L)2 , where 9R and 9L are the Cabibbo angles for the RH and LH sectors respectively. In non-"manifest" LRS models 8R is not necessarily equal to 0L. Therefore Ku2 might be more sensitive to X than JEJJ.2, if /sin0R/ happens to be close to 1.0. Both data are valuable to constraint X and 0R. What we can observe in the actual experiment using positron asymmetry of integrated spectrum, is the product, ^Pn , and a deviation signal 1 + £PM. = 2 \2 { 1 + ( sin0R/sin0L)2} is looked for, since Z, = 1 - 2A.2 in the LRS model. In Fig.l the situation is illustrated. More general discussion taking into account boson mixing angle £ is straightforward. 2. Kn.2 muon beam method In the previous experiment, E99, a K+ beam was transported as a separate beam and stopped in a target. Positive muons from the subsequent K+ decay were magnetically analyzed and then stopped in a thin Al target placed in a transverse magnetic field for muon spin rotation (|iSR). The asymmetry of the integrated positron spectrum was determined from the oscillation amplitude of a time spectrum. The accuracy of the measurement was limited by the statistical error because only 10^ events could be used in the final analysis. Disadvantage of this kaon-beam method is relatively small event rate one can achieve. Particularly, because of beam broadning after a thick kaon-momentum degrader, the emitted muons have a wide momentum width. Since a |xSR target should be thin to avoid significant multiple scattering of positrons, the stopping fraction is not large. Furthermore one has to take into account muon collection efficiency unless a sofisricated 4ft apparatus is introduced. In order to overcome such disadvantages and to increase the counting rate drastically we developed a new technique, so called Kp.2 beam method. It is the use of K+ analogue of the surface muon beam. Low energy part of the kaons produced in the 12GeV proton reaction stop in the production target. Muons from the at-rest decay having 235 MeV/c momentum are transported through a specifically designed muon channel . This kind of beam has been used for the -136 — cross section measurement of subthreshold K+ production at lGeV proton [7]. The experiment is then essentially the beam polarization measurement. With this method we benefit by the following advantages; 1. we obtain high muon intensity (more than in the kaon-beam method), still satisfying the conditions of 2. very sharp momentum width of the beam wiui the consequence of high un stopping efficiency in a thin U.SR target and of low background, and 3. very defined beam spot which enables us to construct a compact experimental set-up. Thus it is easier to eliminate or estimate systematic errors in results. In this way we obtain a counting rate of positron 100 times more than in E99. It is possible now to aim at an accuracy of 1.0 % in the determination of £Pn. For realization of this method there were some points to be solved. Can we surely identify muons in the beam and perform a uSR measurment in the presence of huge pion flux? How can we eliminate the backgound muons in the beam which originate from the in-flight decay of pions in the beam channel. We solved these questions by designing a new beam channel based on quite unusual concept. This channel satisfies the above requirements and enabled us to start a high precision experiment of polarization. 3. Muon channel The layout of the constructed beam channel is shown in Fig.2. It consists of 3 bends and 6 quads and has a length of 13.6m. Main features of the channel are: 1. backward extraction angle, 2. short distance to the first bend, 3. high momentum resolution, 4. thin production target, and 5. long straight section for TOF. Main parameters of the channel are summarized in Table 1. Some details of the design principle are described in the following. (1) Backward extraction In order to reduce pions in the beam and suppress the muon contamination originating from their in-flight decay which contributes to the continuous background in a momentum spectrum, a small pion production rate is essential. Although the angular distribution of pion production at 12 GeV is not well known, it is reasonable to consider a backward angle to be advantageous. If we assume the same behaviour of the angular distribution as 8.9 GeV/c data from Dubna [8], we can expect a pion reduction of factor about 3 even compared with 90O for 200 -250 MeV/c (Fig.3). (2) First bend Most part of the background source is the 7t^2 decay between the production — 137 — target and the first bend, since mere is no means to discriminate such muons with the same momentum. Therefore a short distance to the first bend is important. In our design a sector type bend was put as the first channel element very close to the production target. (3) Momentum bite Because the momentum spectrum of the in-flight %u2 background is continuous whereas me Kp2 fro™ the target is monochromatic, it is necessary to make momentum bite as small as the intrinsic width of the monochromatic peak. In order to realize this condition we put two intermediate horizontal focuses with large dispersion. A momentum bite of Ap/p = ± 0.6% was attained using two slits. (4) Thin production target The continuous muon background cannot be eliminated completely. Its contribution to the asymmetry is to be corrected by measuring the asymmetry of the backbround at the both sides of the peak. For this purpose the peak width observed when we sweep the channel setting must be as small as possible. This width is determined by the channel momentum bite and the energy loss distribution in the production target. We selected a platinum plate of 1.5 mm thickness. The momentum width corresponding the energy loss is Ap/p = ± 0.8 %. (5) Long straight section A long straight section is inserted at me end of the channel. It serves as a TOF section with relatively small flight path difference which determines the time resolution of the TOF measurement. As a result we are observing a very sharp peak in the momentum spectrum with a width of Ap/p = ±1.0 % ( Fig.4). The continuous background is reduced to about 2% of the peak hight. Beam intensity of 1700/ 10l2protons on 8 cm x 8 cm spot (total flux is 3500/ 10l2protons) was obtained. The performance of the channel is summarized in Table 2. Fig.5 shows the JC+ and e+ yields as well as negative polarity case. 4. (J.SR measurement The beam polarization is measured by means of a conventional transverse- field |iSR method. The experimental set-up is shown in Fig.6. The TOF is measured between the second intermediate focus and the apparatus with a 7 m interval. A typical TOF spectrum is shown in Fig.7. The separation of nr+-/fi+/e+ is complete. The channel is equipped with a drift chamber after Q6 for beam tracking. Incident muons are detected with a drift chamber of three (x,y) planes and incident angle is determined. The beam is then moderated and stopped in a 3mm thick Al target. The muons suffer multiple scattering in the degrader, the deflection angle is measured with two sets of MWPC's with a (x,y) plane. Associated spin rotation is corrected for. Fig.8 shows the range curve for -138 — 7t+/u+/e+. The Al target has a purity of better than 5N and a size of 17cm x 30cm, and placed in the 20cm gap of a magnet which produces 100 Gauss of transverse field. Decay positrons are detected at both sides with box type drift chambers with four (x,y) planes each and a trigger counter system. The positron emission angle is measured very precisely. The threshold of e+ detection is low enough and we measure the integrated asymmetry from the oscillation amplitude, Ae+, of a u\SR time spectrum. The quantity, ^Pp., is related to Ae+ as §PR = -3Ae+. It is essential to observe a clean (i.SR time spectrum with low background to be able to determine the amplitude with a small error. Several cares were taken, for instance beam-pileup and e+-pileup events are rejected, and also scattered events from the magnet pole pieces are rejected. As a consequence we succeeded to follow the muon decay up to 13.5 u.s without disturbance from a constant background. An example of a time spectrum with only small accumulated events is shown in Fig.9. We have to think about possible depolarization mechanisms from the beginning in the production target. When muon beam scattering takes place a small amount of spin rotation accompanies [9]. While the scattering from the production target, metal foil of the beam duct windows and the Al target are negligeble, we cannot ignore the degrader of 30 cm thick graphite. This effect as well as the e+ scattering emerging from the Al target should be corrected. 5. Conclusion We have just started a measurement and after several tune-up of the apparatus and the beam, the experimental condition is now as was designed. In the allocated beam time of 100 shifts (800 Hrs) we may collect enough events including runs of background muon asymmetry. One million events for the final analysis would yield a statistical accuracy of 0.5%. If we can check systematic errors down to the same scale, an overall experimental accuracy of 1.0 % is promising. The possibility is mentioned that the confirmation of a KJJ2 monochromatic beam at 12 GeV proton accelerator may open new applications, even though its intensity and stopping density are still limited compared with the surface muon beam from 7tn 2 decay. Acknowledgements The author is thankful to the El95 collaborators ( Dr. Y. Kawashima, Dr. H-.K.Tanaka, Dr. E.Takada, Dr. H.Tamura, Mr. M. Aoki, Mr. H. Outa, Dr. M. Iwasaki, Prof. R.S. Hayano, and Prof. T. Yamazaki) for daily discussions, and to Prof. K. Nakai for encouragement and useful discussions. — 139- References 1. J.V. Klinken et al., Phys. Rev. Lett. 50 (1983) 94 H. Abramowicz et al., Z. Phys. C. 12 (1982) 225 2. D.P. Stoker et al., Phys. Rev. Lett. 54 (1985) 1887 3. I. Beltrami et al., Phys. Lett. 54 (1987) 326 4. G. Beall et al., Phys. Rev. Lett., 29 (1982) 848 G. Beall and A. Soni, Phys. Rev. Lett. 24 (1981) 552 5. J. C. Pati et al., Phys. Rev. Lett. 31 (1973) 661 M. A. Beg et al., Phys. Rev. Lett. 38 (1977) 1252 6. R. S. Hayano et al., Phys. Rev. Lett. 52 (1984) 329 T. Yamanaka et al., Phys. Rev. Lett. D34 (1986) 85 7. N.K. Abrosimov et al., JETP Lett. 36 (1982) 261 8. A. M. Baldin et al., Dubna Preprint El-82-471 (1982) 9. V. L. Lyuboshits, Sov. J. Nucl. Phys. 31 (1980) 509; 32 (1980) 362 Table 1 Parameters of the muon channel Production target Pt Target size 1.5tx6.0wx20hmm3 Extraction angle 150° Solid angle 10 mstr. Maximum momentum 260 Mev/c Momentum bite ± 0.6% First horizontal slit ± 0.5 cm Second horizontal slit ± 0.4 cm Beam line length 13.6 m TOF section 7.0 m Table 2 Summary of Kn2 muon beam Total muon flux 3500/1012 protons Muons with TOF I.D. 1700/1012 protons Tt/u, ratio on peak 0.77 Momemtum width ±0.8% Peak width ± 1.0% Peak/B.G. ratio 50 -140 — 7 i I i x i i i " I — 1 , \ \ \ KEKE 6 - i\\ \ \/ " i \ \ \ \ Limit from 5 \ \ \ \ \ |1/s;neL - p: 4 N = to - \ \ * y / - ^ ~ Pi i 3 \ \ \/V \0.90 i 3 \ \l < \ 0.94 2 - \ f\ / %> "-- NJ M "^0.98 "^-^ 1 TRIUMFJ XLS^^JJ^"^-^.^- 1 "v-i0.995 """^ 0 1 1 II II xl 1 1. 0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 A = (MWL/MWR)2 Fig. 1 Constraints on the square of boson mass ratio, X, and the ratio, b, of the sin of the Cabibbo angle by measurements of EJ?^. Fig. 2 Layout of the new muon channel constructed for the muon polarozation experiment. -141- - I I I I 102 _ : § 1 x a - K Q 10l r- z : x * » * : o o 10',0 __ 10- 1 . I I ! I [ I I I I I 1 I I 1 I I 1 ! L t L 200 400 600 BOO p(MeV/o) Fig.3 The ratio of pion production cross section at 90° to that at 168° by 8.9 GeV/c proton at Dubna for several different targets [8]. -1 ' ' ' ' 1• T—r • i—i—|—i—i—i—i" i—i—i—i—i—|—r i—r—I r i • I I " < : 1500 a ' o o i 1 • ft 1000 - —* — - <• w 500 — PS «i < > PS o PS '1 , , , , I ' ' ' I ' **-*—**-* * .9 ? ? ^Tj ' ,%0» i a j> i n a 125 150 175 200 225 250 Momentum (MeV/c) Fig.4 Momentum spectrum of the muon beam. -142- 2500 i i I I i i i i I i i i i—I i i i r 2000 I— cw o (o- 1500 ft CM *H Ed O 1000 N 600 ! "T—*—* . ?>' + 210 220 230 240 250 260 Momentum ( MeV/c ) Fig.5 Intensity of the muon beam in comparison with other beams. e+ COUNTER DRIFT CHAMBER G$ DRIFT CHAMBER Fig.6 Experimental setup of the polarization measurement 143- total 6165. counts mean 1403.96 chan Time Difference of TOF 660. 1" 1 1 II 1 1 II i 600. 540. - — 480. — - 420. — - 360. — T — 300. — , - 240. — — — 180. 1 — 120. + 60. 6 I i i . _i I r\ i i i 1200. 1250. 1300. 1350. 1400V. 1450. 1500. 1550. 1600. 1650. Fig.7 TOF time spectrum T1-T2-T3 100000 — soooo -i 60000 •3 m 40000 — 20000 — IS 20 25 30 Thickness of graphite degrader in cm Fig. 8 Range curves for the beams -144 — muSR on target left xCALLS- 9067 c o 5; 1/j c 3 o o muSR on target right «CALLS- 9166 "T 10" - U) c o -a- c o u 10' - 10' Fig.9 A typical |iSR time spectrum — 145 — Dynamical CP Violation Yoshio YAMAGUCHI Tokai University Though CP violation has conventionally been treated in such a way that the Kobayashi-Maskawa quark mixing matrix (with CP phases) is introduced into the CP conserving electro-weak theory (i.e., the Standard Model (SM)), an alternative approach, a dynamical CP violation, will be studied here. CP violation is assumed to be due to CP violating Yukawa interactions Hy mediated by spinless boson(s). Namely, our Hamiltonian is supposed to consist of QCD Hamiltonian, CP conserving electro-weak Hamiltonian with the real Kobayashi-Maskawa matrix (without CP- phases) and H„. There are two possible types of Hx, (a) P and T violating and (b) C and T violating. It turns out the type (a) is acceptable. To be consistent with existing experimental data, Hx couples only to quark and should not change quark-flavours (except u++d). Examples of Hx are fi^j(1+iY5)qj* ' (1) where $ is a neutral spinless field with mass m. Application to K°-K° systems of such a dynamical CP violation (1) leads to the effective strength f2/m2 - 10"3 , — 146 — of CP -violating forces, the second order effects in H„. The long-lived K, is shown to be dominantly pseudoscalar K2 with a tiny mixture of scalar K- and all data on neutral kaons can be fitted. Then all hadrons and nuclei will contain a small parity -•3 -11 mixture, whose amplitudes are of the order of 10 -10 . (1) predicts the CP phase to be 90°, so that the parity violation effects based on (1) will not show up in most of conventional P- tests in particle and nuclear physics. Whereas P and T violation due to (1) predict new contributions in processes such as n •*• ir ir 0 + - IT + e e K, * e e and u u due to their scalar admixtures. It is interesting to see whether TRI holds or not (and especially CP phase is 90° or not) in n- 1 39L a collision, where a large heliclty asymmetry was found by Moscow and Kyoto-KEK groups at the resonance (0.74eV). A full account of the present work will be published soon in J. Phys. Soc. Japan and Proc. of CP violation in particle physics and astrophysics, 22-26 May, 1989, Chateau du Blois, where full references will be found. -147- From the KEK-PS to a KAON Factory A bridge to a new era of KAON" Physics. K. Nakai and T. Sato KEK, 1-1 Oho, Tsukuba, Ibaraki 305, Japan The 12-GeV proton synchrotron at KEK (KEK-PS) was built in 1976, as the first major high-energy accelerator in Japan. Originally, the proposed energy of the synchrotron was 40 GeV, and when approved, the energy was lowered due to budgetary limitation. It was a neces sary compromise to start the high-energy physics project in Japan. This choice of energy has made difficult to make significant contributions to particle physics under the severe competi tion in high-energy physics. Nevertheless, high-energy physicists made all efforts to develop Japanese high-energy physics with the KEK-PS until the e+-e~ collider, TRISTAN, became available. In the first decade the KEK-PS has been "the playground" in high-energy physics, and the many young physicists trained through the PS experiments became major driving force of the TRISTAN project. Since 1985, the KEK-PS program has been switched toward "KAON* physics" including nuclear physics experiments, such as hypernuclear physics, pion physics and so on. The new programs are still in an early stage, and some fruits of the programs are gradually accumulating. Present activities are briefly summarized in the next section. The prospect of the KEK-PS in near future is seen in the Japanese Hadron Project(JHP). The project includes upgrading of the PS beam with use of a 1-GeV proton LINAC as an in jector, and the construction of a new experimental area. Although, with this improvement, we can only reach to the present AGS beam intensities, a number of efforts are being made in the beam-line and spectrometer designs to make efficient use of the beam. Already construction of a new counter hall and large acceptance spectrometers has been started. Plans and expected performances are described in section 2. Further improvements of the KEK-PS have been investigated in the process of writing the JHP proposal. Possibilities such as building a stretcher ring to increase the beam intensity have been studied. However, it was concluded that such an investment would not have a good return, and the main emphases of the JHP are placed on other proposals. It is, therefore, natural to see future extension of the KEK-PS programs in a KAON-factory project. In section 3, we shall discuss our interest in the TRIUMF KAON factory project in view of our KEK-PS program. ' * The word KAON stands for Kaons, Aniiprotons, Other hadrons and Neutrinos. — 148- 1. Present Activities at the KEK-PS. Beams and beam-handlig technologies. A layout of beam lines and a list of available beams at the KEK-PS are given in Fig.l and Table 1, respectively. Generally the intensities of the secondary beams are about an order of magnitude smaller than those of the BNL-AG5. It is because the primary beam energy is lower (12 GeV vs. 32GeV), and beam intensity is lower (lxl012pps vs. Ixl013pps). In addition, the emittance of primary beam is larger because the acceleration energy range for the adiabatic compression after the transition energy is smaller. The beam-channel group, however, is proud of the beam quality. In particular, the DC separator developed by them provides good particle separation power. Recently, the K/TT ratio of 1/3 was obtained for negative-particle beams at 1.5 GeV/c. Such a kaon-enriched beam was indispensable for the hybrid-emulsion experiment for (K~,K+) reactions. The group also experienced construction of a superconducting beam line, irl (now closed). Since the construction of the xl beam line, superconducting technology has grown up at KEK under cooperation with Japanese industry. Three large-scale solenoid magnets were built for the TRISTAN detectors, and are being operated without any major trouble. The technology is also being extended to build the Astromagnet, a magnet with a persistent current mode to be sent into the space. In our PS activities, two superconducting magnets are being constructed as discussed in the next section. Physics programs. A list of on-going experiments at the KEK-PS is given in Table 3. Among the variety of programs, relevant subjects to be considered in terms of a KAON factory project are the Kaon rare-decay and the hypernuclear studies. Kaon Rare-Decay Experiments Currently, the rare-decay search for KL -»jxe (E137) is going on at the KEK-PS. Due to the limitation of beam intensities, the competition with the AGS experiment (E791) is very severe. However, in such a case of very difficult experiment it is desirable to have independent experiments at different institutes providing that the experiment at the KEK-PS can make a significant contribution. In order to achieve the comparable contribution as the AGS exper iments, the policy of program coordination is chosen carefully. Considering the limitation of beam, only one experiment at a time is carried out with the highest priority. After finishing + E137 in the summer of 1989, the CP experiment (E162) to search for the KL -* ir°e e- process will be started. The KL -y fjie search (E137) was approved in December 1985, and after two years of construction of the beam line and detector systems the data-taking was started in December 1987. The system has been tuned up to the best condition with a good mass resolution and highly reduced background. The data-taking will be continued until summer 1989 with the highest priority. The following is a comparison of three experiments. -149- Experiment Mass resolution Sensitivity Sensitivity Sensitivity a(Mm) Achieved(1988.12) Expected(1989.8) proposed KEK E137 1.3MeV 7xl0-10 8x10-" 1x10"" BNL E791 1.4MeV 3xl0"10 2x10"" 0.5xl0"12 BNL E780 2.3MeV 1.3xl0"9 lxlO"10 Although the experiment E137 will be switched to the CP experiment E162 in the coming summer, the group is considering to measure the longitudinal polarization of y. from KL —* p-p decay with a new setup and a new beam line in the new experimental hall which is under construction. In this second phase of the experiment they will try to lower the sensitivity of Ki —»fie search further down with more technical improvements. The experiment E162 to search for the CP-violating KL -* 7r°e+e~ decay will begin in the fall of 1989. This experiment is also under severe competition with a Fermi-Lab. ex periment. The goal of this experiment is to reach a sensitivity as low as 10~u, which will be attained by a data-taking run as long as one year from the fall of 1989. The group has started various developments to obtain the best data-taking conditions. Among them are a test of pure CSI crystals to obtain fast response, design of a pipe-line TDC with use of newly developed 1-GHz shift registers, modification of the PS-magnet power supply to improve the duty factor of the primary beam etc. Over several years, considerable efforts has been and will be paid to develop the experi mental system to handle extremely high event rates and to select extremely rare events from enormous background. Such efforts are also along the line of technical developments at KEK for experiments at the high-energy hadron colliders, the B-factories, as well as the Kaon fac tories. The K-decay experiments are one of the very important motivations which stimulate the technical developments. Hypernuclear Experiments In the past several years, the hypernuclear experiments have been the central program of nuclear physics at the KEK-PS. Being supported by the Japanese group of nuclear structure theorists, a strong program of hypernuclear studies has been started. Instead of the traditional method of recoilless hypernuclear production, the stopped-K and (TT+,K+) production meth ods are being used. Being stimulated by the observation of narrow peaks in the (K~,ir~) spectra of 9Be at the position corresponding to a E-hypernucleus by the Heidelberg group at CERN, the S- hypemuclear production via the stopped-K method has been studied extensively. According to the experimental group, however, they have not observed any narrow states of E-hypernuclei except for the He target, in which case the S wavefunction seems to be pushed out from the nuclear potential due to an isospin dependent term of the E-nudeus interaction (Fig.3). This conclusion discourages the S-hypernuclear study with the stopped-K method, leaving the original puzzle of the narrow states observed at CERN unsolved. In order to solve the puzzle, it will be necessary to repeat the original (A'_,ir~) in-flight experiment. It is, however, diffi cult at the KEK-PS because the in-flight experiment for E-hypemuclei requires high-intensity low-momentum K~ beam, and the puzzle is left for the Kaon-factory experiments. - 150 - The other hypernuclear program at the KEK-PS is (ir,K) spectroscopy which was origi nally started at the AGS. This experiment with a pion beam appeared to be best suited for the KEK-PS, since there is no handicap due to the beam intensity. The angular momentum effects in (x, K) reaction due to the momentum mismatching are noted to make this method unique and useful in populating hypernuclear states selectively. A number of interesting ex periments have been proposed, and a fruitful program is anticipated with this method. It is a good question to ask whether the Kaon-factory beams would open a new possibility in the (w, K) spectroscopy. A possible use of the high-intensity pion beam from Kaon factory would be to supply a beam with an extremely good resolution, say 10 keV. A spectrometer with a new concept would be required. It is also necessary to build a physical justification for the high-resolution hypernuclear physics. Although the production of exotic particles or hypernuclei with the strangenes -2 is very interesting, the present kaon intensities at the KEK-PS are not sufficient to plan any major experiments. Recently, however, an experiment to search for AA hypernuclei and/or the H-partide (E176) is going on with use of the hybrid-emulsion technique for the (K~,K+) reactions. This experiment is hoped to be a pilot for Kaon-factory experiments. 2. Improvement of the KEK-PS via JHP Construction of a New Experimental HALL - The JHP KAON Arena. In order to extend the present activities and to support the wide variety of experimental programs, a new experimental hall is being constructed at the area of the old beam line for the bubble-chamber which had been closed several years ago. A layout of the new experimental hall is shown in Fig.2. It will be completed in December 1989, and installation of two beam lines, K5 and K6 will be started in 1990. Two large acceptance spectrometers are being constructed and to be installed at beam lines K5 and K6. A superconducting toroidal spectrometer with 12 gaps to cover a low momentum range will be installed at the K5 line, and a SKS spectrometer with a superconducting large-gap dipole magnet to cover a higher momentum range will be used at the K6 line. Expected per formances of the beam lines and spectrometers are tabulated in Table 2. These spectrometers were designed to realize large acceptances and medium resolutions at high momenta, by the use of superconducting magnets. The Toroidal spectrometer will be used mainly for stopped-K experiments, such as A- hypernuclear spectroscopy and rare-decay studies of charged kaons. The SKS spectrometer will be useful for (TT, K), (K~, K+) and (vr^ir*) spectroscopies with use of GeV pion or kaon beams from the K6 line. Thus the new counter hall will become a center of KAON physics at the KEK-PS. When the JHP will be started, the new counter hall will be nothing but the KAON Arena of the project. — 151- Expected Improvement with the JHP. One of the main components of the JHP is construction of a 1-GeV high-intensity proton LINAC. When a beam is injected from this LINAC to the PS, the primary proton intensity will be increased by a factor of 5 to 6. Since an improvement of beam emittance is also expected, the increase of secondary beam can be as large as a factor of 10. The beam lines in the new experimental hall, the KAON arena, were designed to handle the high-intensity beams. Combining the PS-beam upgrade and the spectrometer constructions, improvements of experimental conditions are anticipated by a factor of more than an order of magnitude. 3. From the KEK-PS to a KAON Factory A natural extension of the present KEK-PS programs is to use a Kaon factory. Since the Japanese Hadron Project does not cover Kaon-factory physics, the TRIUMF KAON factory proposal is very attractive for the KEK-PS physicists. Many developmental efforts for the KEK-PS experiments could be more fruitful, if continued to a KAON factory. There must be much room for Japanese physicists to contribute to the TRIUMF KAON factory project based on their experiences at the KEK-PS. It is also very important that the mutual cooperation between Canadian and Japanese physicists stimulates KAON physics not only at TRIUMF but also at KEK. A KAON Factory Project as a Goal of KEK-PS Experiments. Kaon Rare Decay Experiments. The search for kaon rare decays must be the central program at a Kaon factory. There is an obvious limitation in the KEK experiments due to the beam intensity, and therefore, the experimental groups who are involved in the high-sensitivity experiments with high-beam intensities must realize their goal in Kaon-factory experiments. With a Kaon-factory beam of a factor of 100 or more in intensity, the sensitivity of the Ki —v y.e search could go down to 10~13. Although the present CP experiment may be able to observe the CP-violating Kr, -* 7r°e+e~ decay at the level of 10-u. more detailed studies of the CP violation can be done with a Kaon-factory beam. It should also be noted that the experiments at a Kaon factory with the extraordinary high beam intensities must face enormous difficulties in handling the high counting rates. Experi mental techniques would be much beyond the present level. Various techniques would not be able to be developed in a single step, but would have to be accumulated step by step. We would like to see that KEK experiments form a base for this experimental development. Experi ences with beam-line construction, high-rate detector systems, high-speed electronics and data acquisition systems in the KEK-PS experiments would be vitally important for Kaon-factory experiments. -152- Experimental Programs not Attainable with the KEK-PS. Hypernuclear Experiments There are many experiments to be done with the KEK-PS beams on hypernuclear studies, but also there are many experiments which are not attainable with the KEK-PS. Examples of hypernuclear experiments which require the Kaon-factory beams are: (1) Double-strangeness hypernuclei ; H-particle, AA-hypernuclei and E-hypernuclei, etc. With the high-intensity K~-beam from a Kaon factory, spectroscopic information on the double-strangeness nuclei would become available from measurements of the (K~, K*) reaction with a reasonable resolution. (2) In-flight (K~,it~) experiments on E-hypernuclei. As discussed earlier in p.3, the puzzle of narrow peaks observed at CERN has to be solved with the in-flight (K~, v~) experiment with a high-intensity If "-beam. If the peaks were confirmed to be due to E-hypernuclei, there would be many interesting possibilities. (3) High-resolution (AE < lOQkeV) spectroscopy with the (K~,ir~) and (7r,K) reactions. The high-intensity beam from a Kaon factory would make high-resolution studies of hypernuclear states possible. It would be also interesting to study excited states of far-off-stable-line nuclei via. (?r-,7r+) reactions. Possible Scientific Contributions to the TRIUMF KAON factory from the KEK-PS. As discussed above there are a number of reasons that the KEK group is interested in the TRIUMF KAON-factory proposal. The high-intensity beams are most attractive for ..the K-decay experiments.-- Experiments for double-strangeness states also need higher in tensity. There must be wide varieties of physics that the KEK physicists can contribute to the proposed TRIUMF KAON factory. There are also many possibilities on the technical aspects that the KEK group would be able to contribute to the TRIUMF KAON-factory project based on the experiences at the KEK-PS. (1) Accelerator. Needless to say, there are many experts in KEK on the 12-GeV proton synchrotron and the 500-MeV high-repetition booster synchrotron as well as on the source and injector. Collaborations on various levels can be considered from the exchange of experts to that of technical information. The KEK-PS itself could be used, for instance, as a test ground for practical designs of the Kaon factory and associated facilities. (2) Beam handling. The KEK beam-channel group has a quite extensive experience on the separated beam lines. The DC-separater developed by the group is the world's best. On the other hand, the group is learning about the remote-handling system from TRIUMF. A collaboration and exchange of information would benefit both TRIUMF and KEK. (3) Superconducting technology. Superconducting technology would become very important when high-resolution beam lines and spectrometer systems for GeV particles are to be constructed. The KEK beam- channel and low-temperature-facility groups are very experienced. — 153 — (4) High-speed high-rate detectors and data-taking systems. Considerable efforts have been made for development of high-speed high-rate systems. The present technology is not sufficient to manage the Kaon-factory experiments. Further development must be made step by step in practical experiments. The KEK rare-decay experiments are providing a good test ground. Summary. In this article we have discussed a KAON-factory project as a possible extension of the KEK-PS programs. The subject was, therefore, limited mainly to the experiments using K- meson beams. The physics program of a KAON factory must be much broader. For instance, experiments with antiproton and neutrino beams are other possible programs. The Kaon fac tory provides a wide variety of attractive possibilities. If the KEK-PS physicists are to be involved in a KAON-factory project, however, it would be preferable to follow the line of their current programs to use the fruit of efforts accumulated in the KEK-PS experiments. Technical contributions must be also based on the experiences accumulated in past programs. In order to promote a good collaboration between KEK and TR1UMF on the Kaon factory, the cooperative programs must be mutually beneficial. Since continuous efforts for improve ments of the KEK-PS are going on and the JHP will require much effort in the near future, the collaboration with TRIUMF should be planned carefully. It should be noted that the cooper ation with TRIUMF would also benefit the KEK projects. Exchange of technical information and stimulation of physics ideas are always beneficial to both projects. Finally, it should be emphasized that the promotion of the KAON physics must be made on world-wide basis. Building strong groups with good physics ideas and good experiences must be most important for justification and promotion of a KAON-factory proposal. The most important contribution of KEK-PS would be to stimulate the physics and to provide opportunities for pilot experiments. The collaboration may also include possibilities that Canadian physicists come to KEK to join relevant experiments and technical developments. We would be happy to see that the KEK-PS plays the role as a bridge to a KAON-factory project. -154- Table 1. Summary of KEK-PS Beam Lines. Beam Particles Momentum Momentum Typical Intensity Range Bite: Ap/p (particles/pulse*) (GeV/c) (%) @ lQUppp) K2 K+ 1-2 ±3 5.0x10° © 2GeV/c K~ 1.0x10s ff+ 0.5-2 ±3 2.2xl07 «•" 1.5x107 p 1.5xl04 p 1.7xl07 A'3 K* 0.5-1 ±2.5 4.2xl04 @ 0.55GeV/c K~ l.OxlO4 ir+ 0.3-1 ±2.5 5.0xl07 v- 5.0xl07 p 3.5xl02 p 7.0xl07 K4 P 0.4-0.8 ±3 7.0xl02 ® 0.6GeV/c A'O n 2-8 - 3.0xl07 :r2 1-4 ±1 2.0x10° @3GeVfc 1.0x10s s Vfl 7T~ 0.1-0.45 ±6 1.2x10 ©Q.25GeV/c Tl 0.5-1 ±5 5.0x10" @ lGeV/c 4 7T~ 4.0xl0 T3 1-6 ±5 1.0x10' @5GeV/c 4 5T- 4.0xl0 PI po/.p 3.5 ±0.5 1.0xl0a pol.= 40% P (3-)13 (t 2.5 particles/pulse = 1 particle/sec) Table 2. Beam Lines and Spectrometers in the New Counter Hall. Beam Line K5 K6 New K0 Momentum Range (GeV/c) 0.4-0.6 0.5-2.0 2-8 Momentum Bite Ap/p (%) 3 3 Beam Intensity (pps) A'+ 1.0x10s 1.5x10s (expected) K~ 2.5xl04 5.7xl04 1T+ 3.0xl08 IJxlO7 8 7 ff- 2.3xl0 1.4xl0 Spectrometer TROIDAL SKS Momentum Resolution Ap/p (%) 0.2 0.1 Maximum Momentum (GeV/c) 0.3 1.5 Momentum Bite Ap/p (%) (0.1-0.3) 20 Solid Angle (msr) -100 100 -155- Table 3. A List of Current KEK-PS Experiments (November 1. 1988). Exp. No. Spokesperson Title Status E137 T.lnagaki(KEK) Study of Rare Decay KL -V pe. Running E150 O.Hashimoto(INS) Study of Hypernuclei via (ir+,/lf+) Reactions. Analysis T.Shibata(Osaka) Study of Pion-lnduced Double Charge Exchange E157 T.Kobayashi(KEK) Reactions and Double Pion Production using Analysis a Large Solid Angle Spectrometer. E162 K-Miyake(Kyoto) Measurement of CP-Violating Direct Amplitude Preparation in K\ -~> ir°e+e_ Decay. E163 H.Kaji(Tohoku) Studies of w~ Particle Transfer Mechanism of Analysis Ionic Solution and Mixed Gas System. E167 R.Hayano(Tokyo) Search for a S Hypernuclear Ground State Analysis by Kaon Absorption on Helium-4. E173 J.Chiba(KEK) Study of A Production in Nuclei using Running (p,n) Reactions. E174 L.Northdiffe(Texas) Ay(E,6) Measurements for NN Reactions. Analysis E175 T.lshikawa(Tokyo) Survey of A Decay Lifetime in Heavy Nuclei. Analysis E176 K.lmai(Kyoto) Search for AA Hypernuclei and/or H-Particle Running E179 T.Tsuru(KEK) Study of the jpr* Resonance Preparation -Search for l=l,Jpc=l-+ Exotic States. E187 I.Arai(Tsukuba) Study of Backward A Production in High Energy Preparation Hadron-Nucleus Reactions. E195 J.lmazato(KEK) Precise Measurement of y.+ Longitudinal Running Polarization in the Decay of K+ -*• p+ + v. -156- c _E D. LU V 01 3 o bo -157- Fig. 2: The new counter hall and two spectrometers under construction. a) *He(stopped K".JT~) b) *He(stopped K".ir*) •. ..I.J...I|....|..M 1 | P"i""i""i""r 400 '_ B^ (U.V) Bc-(U»VJ it a -to to a -!• > 300 o 2 KwL 1 : II' . d J -•• / W 1.1 i^/>K—i ' •'•••'••••'••••'••• 250 2fl0 270 230 230 2«0 270 230 290 Mm " MA (MeV) MHT - MA (M<*V) Fig. 3: The AHe(Stopped — K ,*•*) spectra. -158- DISCUSSION OF PARTICIPATION POSSIBILITIES AT KEK D.R. Gill TRIUMF, 4004 WesbrookMa.il, Vancouver, B.C. V6T 2A3 Abstract A group of physicists at TRIUMF have been meeting irregularly since last fall (1988) to discuss options for involvement in experiments that relate closely to the physics that would be undertaken at the impending TRIUMF KAON Factory. Several TRIUMF physicists are already involved in experiments at BNL, in rare kaon decays, radiative kaon capture, kaon nuclear total cross sections, hyper- nuclear production experiments and strange dibaryon searches. More TRIUMF physicists will become involved in such projects as TRTUMF progresses towards the KAON Factory. This involvement will take either of two possible forms: 1. Writing a proposal for an experimental project to be carried out at BNL or KEK; finding collaborators at the proposed home institution; designing and building 'some' of the apparatus at TRIUMF that will be needed for the experiment. 2. Selection of an experimental project that has already been proposed for either BNL or KEK where a substantial contribution can still be made to the design and operation of the experiment, designing and building 'some' of the apparatus at TRIUMF that will be needed for the experiment. Recently such a meeting of the TRIUMF Research Scientists was held to discuss the possibilities for involvement at KEK in light of the new facilities that are under construction there or proposed to be constructed as part of the JHP. The topics considered during this meeting ranged from the ion source to the kaon beams. Byron Jennings led off the meeting with a description of his "favorite" ex periment. Fig. 1 shows the resonances predicted by the non-relativistic quark model (from Capstick and Isgur1) and those found in phase shift analysis for odd parity S=-l baryons. The model is in reasonable agreement with all the well known states, except the A(1405), indicating that perhaps something exotic is happening with this state and indeed some people believe this state is not a three quark state but rather an anti-kaon nucleon bound state (four quarks one anti- quark). To unambiguously disentangle the nature of this state it is necessary to understand the whole region from 1600 MeV to 2000 MeV where current phase shift analysis is in strong disagreement. The structure of the higher states puts strong constraints on the structure of the A(1405) through the orthogonality of the states. Measurements of the kaon-nucleon elastic and inelastic scattering in this energy range are needed. — 159 — Uli Wienands explained that TRIUMF people concerned with design of the KAON Factory accelerators are watching very closely the developements at labs such as KEK regarding the transport of polarized proton beams through syn chrotrons. Following a short explanation of what causes depolarization in such machines, he said that perhaps the largest lesson has already been learned from the KEK experience is that if the original machine is built with polarized beams in mind the later achievement of these beams will be much less of a problem. 1500 . 1300 I 1 I I I I 1 A.r E-r r»- r»- A-r E-r 2 2 2 2 2 2 Figure 1: The Negative Parity S=-l Excited Baryons of the N=l Band Some TRIUMF physicists are already "connected" to programs at KEK. For example Paul Schmor described the close cooperation presently occuring among the people working at TRIUMF, LANL, and KEK on the development of laser pumped polarized ion sources. He also mentioned developments in volume cusp H~ sources where TRIUMF, LANL, LBL have been working cooperatively while the KEK people have been watching very closely the developements. George Mackenzie told the meeting that a cooperative effort is already un derway to study the problems that high intensity beams will present for the maintenance of H~ stripping foils. In the case of KAON these foils are used at the point where the beam is injected into the accumulator (A-Ring) while at JHP they will be used in the compressor. A set of foils is to be tested at LANL by personnel from TRIUMF, LANL, KEK and RAL. A discussion of whether current accelerator physics cooperative efforts are "collaborations" in the same sense as that term is applied to fundamental physics experiments followed. The cooperative program that is presently underway between physicists in -160- Japan interested in "Radioactive Beams" and the TISOL group at TRIUMF was described by John D'Auria. He told the meeting how he is presently pursuing an expansion of this cooperation into a full blown collaboration that will extend well into the future, whether a radioactive beam facility is finally built at TRIUMF or at JHP. A fuller description of these facilities and the cooperative efforts is found elsewhere in these proceedings2. The new beam lines (K5, K6) and spectrometers being constructed at KEK were discussed in light of what types of experiments might be run there in the time before KAON is completed. The fact that LESB-I at BNL is occupied by a kaon rare decay experiment that will likely be running for several more years, means that Kl at KEK will be the only facility where the production of hypernuclei via the (7r+,K+) reaction can be profitably pursued. With this fact in mind Dave Gill described two possible experimental programs that might be undertaken using the substantial ir fluxes available from this beam line. These 7r's along with the SKS spectrometer presently being constructed should make it possible to study; 1. The production of E hypernuclei via the (w+,K+) reaction. 2. The Quasi-Free (Q-F) production of A's,S+'s,E°'s and E"'s. Both of these experimental undertakings would use the SKS spectrometer to detect the production of a hyperon; both would also require a further detector system. In the case of the E hypernuclei search this secondary detector system would be used to supress the Q-F A background. In the Q-F production exper iment the extra detector system would be used to study the hyperons that were being produced, i.e. to measure such things as their polarization. Dave Gill also described a low energy kaon scattering experiment that may be possible with 600 MeV/c kaons from the K5 beam line. It would be the first measurement of iTu in the Kd system. It would require a polarized deuterium target of sufficient size to assure that all the kaon beam could be made to pass through it. If such a target were available (one is presently under developement at PSI) the TOF apparatus presently used at TRIUMF for measurements of this type in the 7rd system could be transported to Japan and the experiment possibly completed in as little as 1000 hours of beam time. Chris Oram discussed a new type of 7r°, 7 detector that could be used for (K~, ir°) experiments. Such experiments would lead to the identification of new hypernuclei and would require x resolutions of the order of 1 MeV. A Liquid Argon Detector should make such resolutions possible for 100 MeV 7-rays. A detector of this type might be used jointly with the Torroidal Spectrometer at KEK's K5 beam line. The production of the Hypernucleus would be detected through the ir° decay 7-ray showers in the liquid argon while the decay of that nucleus would be followed with the spectrometer. — 161 — Some TRIUMF physicists decided to pursue these ideas further and if neces sary combine forces at a later date to carry the one that proved to be the most practical to fruition. References 1. S. Capstick and N. Isgur, Thesis, University of Toronto UTPT-85-34. 2. J.D'Auria, (these proceedings). — 162 — Submission to the Proceedings of the EJIRI Workshop, April 3-4, 1989, held at KEK (Japan) Radioactive Beams and Intense Pulsed Neutron Beams: Research Areas for Japanese/Canadian Collaboration at JHP John M. D'Auria Department of Chemistry, Simon Fraser University Burnaby, B.C., Canada V5A 1S6 The proposed Japanese Hadron Project (JHP) as presently envisaged is an exciting, creative concept, possibly allowing for a wide range of studies in many different areas of science. At this workshop many of these in the area of high energy physics have been presented and discussed. The purpose of this report is to present for discussion research areas in low energy nuclear physics, areas in which there is great interest in Canada to initiate collaboration. These involve using the proposed accelerated radioactive beams facility and the pulsed, intense neutron beam. In the report the scientific goals of such a program will be summarized, the approaches to be used described, and possible areas for present and future collaboration indicated. -163- I. Accelerated Radioactive Beams A. Introduction Over the last few years the possibility of producing accelerated beams of short-lived radioactive species has become accepted as technically feasible. The two main methods or approaches to produce such beams are either projectile fragmentation of very energetic heavy ions for high energy (HE) beams, and the ISOL (on-line isotope separator) post-acceleration approach for low energy (LE) beams. A third approach involving transfer reactions with heavy ions has only produced radioactive beams of low intensities. The first method (HE) is illustrated by the facilities at GANIL1, GSI2, and Berkeley , while the LE approach is illustrated by the proposed TRIUMF-ISOL1*, and to a limited extent by the new facility (Under construction) at Leuven . The proposed facilities6 at the JHP include both a HE and a LE project, although only a LE is planned for the first phase7. In subsequent sections the scientific usefulness of such a facility, and the need, value and areas of possible Japanese/Canadian collaboration are discussed. B. Science at a LE Radioactive Beams (RB) Facility There are a number of interesting, unique and new areas of scientific research possible at an LE-RB facility. Many of these are in reality extensions of programs at low energy, nuclear physics facilities, such as transfer reactions, coulomb excitations, elastic and inelastic scattering, etc., only involving very exotic types of nuclei, e.g. 3He, ULi, 56Ni, 11>8Cs, etc., but involving species previously not available as projectiles. The area of greatest — 164 — interest is nuclear astrophysics. There is considerable interest to study the rates of simple fusion reactions as a function of energy from —0.3 to ~2 MeV/u involving a radioactive reactant. A short list of these proposals for study at the proposed TRIUMF-ISOL facility is given in Table 1. These are believed to be of importance in explosive astrophysical phenomena such as novae, supernovae, massive stars, etc. and are believed to play a significant role in such processes as the hot CHO cycle, the rp process, and possibly a non-homogeneous "big-bang". The rates of such sub-barrier reactions cannot be reliably estimated from statistical theory as they are dominated by narrow resonances at unpredictable energies. The only reliable method of measuring the rates of these reactions is through the use of radioactive heavy-ion beams on gaseous targets of either hydrogen or helium. Details of such experiments, including expected yields, can be found elsewhere8. C. The ISOL/Post-accelerator Approach The proposed TRIUMF-ISOL facility1* would be composed of a front-end on-line isotope separator in which radioactive heavy ion beams from up to 75 elements could be generated for injection into a post-accelerator. The intensity of such beams can be quite high due to the rather thick targets that can be used with the incident intermediate energy (500 MeV) intense proton beam. Beams as high as 10-100 nA could be possible if the full 100 |iA beam of protons could be accommodated. The post-accelerator would consist of a first stage RFQ (radio-frequency quadrupole) LINAC producing beams of the — 165 — order of 100 keV/u for injection into a second stage, DTL (drift tube) LINAC. The resulting radioactive beam would have energies variable from 0.3 - 1.5 MeV/u and an energy resolution of 10-3. Figure 1 is a schematic representation of such a facility. The proposed facility at JHP is similar but considerably more powerful. Regardless, because of the similarity of goals and the similarity of approaches, it is of mutual benefit to initiate a collaborative program of research and development to explore some of the technical problems associated with such facilities. D. The Test Isotope Separator at TRIUMF-TISOL The part of the proposed facilities considered most troublesome and the most difficult to understand is the front-end ISOL device. In order to understand the operation of such devices first-hand, TRIUMF has built a prototype facility of the front-end of the proposed TRIUMF-ISOL. This facility, TISOL, is now an operational facility on beam line 4A at TRIUMF. Figure 2 is a schematic representation of this facility while Table 2 lists some of its operational characteristics. Of considerable interest is the development of a stable, sturdy, ion source, able to produce efficiently singly charged ions from many elements, and able to operate over long periods of time so that low cross-section reactions can be studied. Such a possible source is an ECR (electron cyclotron resonance source). Several groups including TRIUMF have initiated the installation of such sources on an ISOL device9. An ECR source has been built and operated successfully off-line at TRIUMF. It will be installed on-line, June 1989, and -166 — commissioned for use. A program of research and development studies will be initiated and is available for collaborative studies and basic physics. E. Summary With the development and successful operation of the TISOL facility at TRIUMF, a number of potential problems at either of the TRIUMF-ISOL facility in the JHP/Lt arena can be studied, perhaps in a collaborative arrangement. These include development and use of thick targets and ion sources to produce optimal/required intensities of radioactive beams, remote handling capabilities, particularly for "hot" (radiation) objects, new approaches to vacuum systems on ISOL devices, shielding requirements, etc. These short-range studies, if done together, can lay the foundation for future long-range collaboration to perform the exciting new kinds of physics possible with radioactive beams either at the JHP or at TRIUMF, wherever such a unique, world-class facility will be built. II. Intense Pulsed Neutron Beams A. Introduction The intense, pulsed neutron beam at the proposed JHP facility will be unique in the world in terms of operational characteristics6. Such a facility is ideal to perform inelastic neutron scattering studies of considerable importance to various types of condensed matter studies. Canada has had a long and distinguished record in such a field of study dating back to one of the first such proposals for such beams, namely ING (intense Heutron Generator), and due to the use of such intense, continuous beam — 167 — facilities as exist at the high flux nuclear reactor at AECL. Unfortunately, such facilities are now old, prone to failure and are being shut down, e.g. the reactor at McMaster University. There exists a strong association of neutron beam users, namely, the Canadian Institute of Neutron Scattering and the development of such future collaboration seems an appropriate action at this time. There exists a wide area of studies to which such a facility can be applied, particularly in condensed matter physics. These will build on the rather active program presently underway at KENS and will open many new areas. C. Summary The Canadian community of neutron beam users are now considering developing collaborations with Japanese scientists for a variety of projects in several areas. A contact person for initiating such collaborations is Prof. A. Arrott, Department of Physics, Simon Fraser University. -168- Table 1 TRIUMF EXPERIMENT 311 TITLE: A Radioactive Beams Facility for Nuclear Astrophysics OBJECTIVE - measure reaction rates for simple fusion reactions of importance to nuclear astrophysics - energy range of interest from 0.2 to 1.5 MeV/u - reactions involve radioactive and isomeric species REACTIONS OF INTEREST REACTION REACTANT ASTROPHYSICAL PROCESS Tl/2 OF INTEREST 0.85 sec A > 12 prod., inhomo- geneous big bang ^(p.y)1^ 9.96 min hot CNO cycle 150(cc,Y)19Ne 124 sec proposed rp-process 18 19 F(p,Y) Ne 110 min hot CNO cycle 18F(p,ct)150 110 min hot CNO cycle 19Ne(p,Y)20Na 17.2 sec breakout to rp-process leakage of hot CNO cycle 21Na(p,y)22Mg 22.5 sec hot NeNa cycle rp-process COMMENTS - all radioactive reactants are predominantly only positron emitters with no unique identifying gamma-ray (except 511 keV) - this is not an exhaustive list of potentially interesting reactions and does not include any isomeric states — 169- Table 2 CHARACTERISTICS OF TISOL OPERATIONAL PARAMETERS (Present) Mass Range A < 300 High Tension 20 kV Mass Resolution 2000 Beam Spot 1 cm2 Ion Sources Surface (good for alkali elements) ECR - off-line operational - on-line (installed June 1989) Plasma - under development RESULTS Using surface source, about 70 isotopes observed from elements - Li, Na, K, Rb, Sr, Ga, In, Cs, Ba, Yb GENERAL INFORMATION Target thicknesses about 10 g per cm Proton Beam Intensity - up to 10 uA — 170 — References 1. C. Detraz, Proc. Int. Sym. on Heavy Ion Physics and Nuclear Astrophysical Problems (Tokyo, 1988), S. Kubono et al, edit. (World Scientific, 1989) p.151. 2. P. Arbruster, H. Geissel and P. Kieule, ibid, p.247. 3. I. Tanihata, ibid, p. 185. 4. J. Crawford, et al, Hucl. Instr. and Methods B26 (1987) 128; "The TRIUMF-ISOL facility, a proposal for an intense radioactive beams facility" (1985). 5. M. Arnould, et al, Proc. Int. Sym. on Heavy Ion Physics and Nuclear Astrophysical Problems (Tokyo, 1988), S. Kubono et al, edit. (World Scientific, 1989) p.287. 6. See, "A Draft Proposal for Japanese Hadron Project", INS, Univ. of Tokyo, April, 1987. 7. T. Nomura, Proc. Int. Sym. on Heavy Ion Physics and Nuclear Astrophysical Problems (Tokyo, 1988), S. Kubono et al, edit. (World Scientific, 1989) p.295. 8. L. Buchmann, J.M. D'Auria, J.D. King, G. Mackenzie, H. Schneider, R.B. Moore and C. Rolfs, Nucl. Instr. and Meth. B26 (1987) 151. 9. L. Buchmann et al, B26 (1987) 253. — 171- The ISOL / Post - Accelerator 5T1BLE ISOTOPE ION SOURCE PCS7- STBIPOEP. ACCElESiTOR HIGH DE50LUTI0N ION 8E»M L'HE RADIOACTIVE ION BEAM DUMP TRIUMF •1 TIS Box 6 Analyzing Magnet 2 Faraday Trunk 7 Analyzing Slits 3 Faraday Cup 8 Electrical Quadrupoles 4 Wire Scanner 9 Electrical Bender 5 Magnetic Quadrupoles 10 Electrical Steering -173- INTENSITI FRONTIER PHYSICS PARTICLE AND NUCLEAR PHYSICS FRONTIERS EXPLORED BY HIGH INTENSITY PROBES H. EJIRI Dept. Physics, Osaka Univ. Toyonaka, Osaka. Japan §1 Frontiers of Particle and Nuclear Physics There are several frontiers of particle and nuclear physics. These frontiers are explored by driving forces (vectors) appropriate to the frontiers. The energy frontier is explored by high energy probes accelerated by high energy accelerators. Here the driving force is the energy E. This is a powerful and straightforward way to find new particles and to reveal properties of fundamental interactions. The intensity frontier is the one which the present workshop is concerned with. The intensity frontier physics is explored by means of high intensity probes obtained by high intensity accelerators. The driving force to explore this frontier is the intensity. This is a kind of high precision frontier. It is indeed very important for both particle and nuclear physics, as discussed in the workshop. The high intensity probes can be used to search for other aspects of particle and nuclear physics, and is complementary to the high energy probes There is another frontier, which I want to call "sensitivity frontier" . By means of very sensitive (high quality and large volume) detectors, one can explore a very rich physics frontier. Non-accelerator physics is a kind of the sensitivity frontier physics. Here the sensitivity power S includes efficiency as well as selectivity. Finally I want to add one more, namely the physicist (brain) power, P. It is essential for developing new frontiers of * Concluding Remark, presented at the Japan/Canada Workshop on Intensity frontier Physics, KEK, Tsukuba, April 3-4, 1989. -174- physics, because it is the physicist brain (person power) that uses the powers E, I and S so as to develop new physics frontiers. We know that a good violin is necessary for good music, but not sufficient. A good music is realized by a good player with a good instrument. The driving force F to explore the physics frontier can be schematically given as F = EK IL SM FN. (1) The weighting factors K, L, M, and N depend on types of the physics frontiers to be explored. The frontiers and the driving powers are schematically illustrated in Fig. 1. Fig. 1, Frontiers of particle and nuclear physics and driving forces to develop then. E, I, S and P stand for beam energy, beam intensity, detector sensitivity and person (brain) power. -175- It should be noted that the total driving power F is not the sum of individual powers, but rather product of them. Thus the intensity frontier physics, which puts much emphasis on I (large L), demands some energy power E and the detector power S as well as the physicist power P. In particular, high sensitive detectors bearing high selectivity of true signals among huge background signals are essential. The physicist power should include both the quality and quantity. Constructive collaboration of n persons (groups, countries) produces a large total power. The intensity frontier physics is a kind of big science, requiring many physicists as well as big facilities. Then constructive collaboration of many physicists is essential. § 2 Probes for Intensity Frontier Physics High intensity (precision) frontiers of particle and nuclear physics are developed by means of probes produced by high intensity primary beams. High intensity protons accelerated by high intensity medium-energy accelerators are commonly used as the primary beam. Secondary particles produced by the high intensity protons are used as probes for exploring the intensity frontier physics. These secondary particle probes are classified for simplicity into the following three types. a. High intensity secondary particles such as K and TT mesons, neutrons, anti-protons, neutrinos and muons. b. High quality probes with high energy resolution, small emittance, and so on. c. Hew (exotic) nuclear probes with large spin, isospin deformation, and so on. The high intensity primary beam can naturally provide high intensity secondary particles in a narrow momentum window and/or a narrow emittance window. The exotic particles and nuclei (c), which are produced with rather small cross-sections, are also provided by the high intensity primary beam. Event rates Ie of reactions (interactions) to be studied depend on the cross-section and the experimental condition. The -176 — number of event N for a measurement time t is written as n N=Iet=IpNt d a e t > 1 or /%. , (2) n where I ,NT, e and d a are the intensity of the probe,the number of target nuclei per cm 2 , the detector efficiency and the differential cross-section, respectively. N has to be larger than either one if there is no background NgG, or the fluctuation /HgQ if NgQ>1 after -severe selections (cuts) of the events. As a matter of fact N is proportional to Ip, and accordingly lower n limit on d 0 to be studied is inversely proportional to Ip. Here one should note that E and /NJJQ, which are concerned with the detector sensitivity, are also important, particularly in case that £ and /ifnn depend on Ip. High quality beams lead to low- background measurements. The differential cross-section is generally written as n n 2 d 0=[d (|<(Uf|H|4,i>| .C)/(dE1,...,dn1..,dt)] XAE-J , .., AJ2-] i "tA^, (3) where H is the interaction Hamiltonian, ^^ and jjjf are the initial and final states, A^-I is the energy window for E^, and so on. Then there are three kinds of experimental studies. A; study of the very weak process (rare process) with small H. by using the high intensity secondary beam. B; study of exotic process <^£.|H|,jj.> and of exotic final states ^ by means of exotic probes ^-. C; study of fine properties of reactions (states) to extract important physics quantities by extensive correlation measurements. This type of measurements requires necessarily differential correlations with many window AE1 > •••AQ-|i ••• A*i leading to the very small differential cross-section. §3 Studies of Rare Decays with Small H (Branching Ratios) There are important rare processes to be studied with high intensity probes in the framework of the standard theory. One is — 177 — the detection of the second order weak process such as Kf*71' °e+e" + + — ,K-cir vv and the other is the high precision check of the standard theory by measuring precisely the sin% , the CP origin through the rare decay of KHr ft ft , and the search for Higgs. The high intensity probe can also be very effective to challange the present standard theory by searching for rare processes such as K -+TT qj , Kj+ue, etc that are certainly beyond the standard theory. The rare process with the small branching ratio B is described in terms of the effective coupling constant G for the new interaction X as where Gp is assumed to be an order of the Fermi coupling constant. The coupling constant G may be expressed by using the mass NL of the X particle mediating the new interaction, 2 Gx=g /M^ . (5) Then B and M are related by assuming g^1 as 8 BI>10 /(Mx/Gev)^ . (6) f The event rate is given as H 'f Br E. Using values of N^-3, •trulO'sec and e^0.3 for a typical experiment, one gets Bjv-H'KT6 . (7) r p The event rate for the corresponding collider experiment is evaluated as IM,«o»fe. (8) Here we use similar values of 1^3, t^107, EM).3 for the collider experiment with the luminosity lM032cm~2sec~1' The cross-section -178- Mx (GeV) S (GeV)' 1 • I L. 10' I02 I03 I04 I05 I06 /s(GeV) Fig. 2. Parameters for a typical example of rare decay studies. Left hand scale is the intensity .if probes (kaon beam intensity), and the right hand scale is the corresponding branching ratio studied by the probe.The solid line shows a relation between the mass (tope scale) of the particle mediating the interaction and the corresponding Br. Bottom scales indicate corresponding energies S and /§" required for the collider experiment. — 179- a is given as o^CxS, where S is the square of the energy. Then one gets, 3 2 Br=2.5-10- /(S/(GeV) ), (9) S=2.5.10-11M/ . (10) The relations of the quantities I , Br, M^, S and /S are plotted in Fig.2. High intensity probes with I =107%1010 make it possible to search for the rare process with the branching ratios of 1 1 Br^10~ \l0~ °, corresponding to the mass range of M^=10-S.KHjeV. The corresponding collider energy of /S=10^5«10 GeV is much higher than the presently available energy. §4 Particle and Nuclear Physics With Hew Probes. New types of secondary particles (nuclei), which are produced by high intensity primary beams, are used to probe for unique aspects of particle and nuclear physics. Neutrons are used to study fundamental properties of particles and interactions. Precise measurement of the neutron life-time is important. The p-wave resonances of the neutron in nuclei are useful for studying P and CP violation mechanisms. Antiprotons can be a unique probe to study P and CP violation mechanisms and to investigate QCD confinement as well as exotic quark systems. Positive kaons K+ are unique for probing directly the internal region of nuclei because they have a long mean free-path in contrast to pions, and the anti-symmetrization is not required in contrast to protons. K is less distorted in nuclei, being free from resonances, and is sensitive to the neutron / proton density distributions. Unstable nuclei are produced by interaction of the intense proton beam with nuclei. They are accelerated to probe for exotic properties of nuclei. The unstable nuclear beam is very useful to study exotic nuclear states with exotic properties such as large — 180 — A (super heavy elements), large N/A ratio, large deformation, and so on, and exotic nuclear reactions which are crucial for understanding nuclear synthesis. § 5 Spectroscopic Correlation Studies with Intense Beams Fine spectroscopic studies of particle and nuclear physics can be carried out by correlation (coincidence) measurement such as energy, angular, time and other correlations. In order to measure these differential cross-sections for finite energy, angle and time windows, one needs the high intensity beam. It should be noted that nuclear structure studies, have been started by measuring singles inbeam-y spectra and have been developed by introducing correlation (coincidence) measurements with high quality light-heavy ion beams. 5.1. Hypernuclei with Strangeness AS=-1 Hypernuclear levels have been studied by measuring singles spectra of (IT , K ) and (K~, ir) reactions. Electromagnetic and weak decays of the hyperon in the hypernucleus are studied by measuring energy, angular and time correlations of decaying particles (y-rays). Electromagnetic moments and transition rates are interesting for studying new kinds of nuclear properties associated with the strangeness (hyperon). Some of them are the effect of strong electromagnetic fields on the Cabibo angle in the hyperon decay, nuclear environment effects on the size of the hyperon in the inner nucleus, short range correlations and heavy meson effects on the weak decays, the S-quark spin response in nuclei, the nuclear deformation induced by the hyperon in the inner S orbit in nuclei and so on. The (ir+, K+) reaction at the momentum range of P(TT+)=1.0- 2.0GeV/c are useful for the decay spectroscopy because of large cross-sections for elementary hyperon productions, large spin polarizations of hypernuclear levels and of large angular momentum transfers, as shown in Fig. 3. It is important to notice that low-lying levels produced through compound (™ > K xnypY) reactions have also the large spin polarization. Such spin -181- 200h (7T+,K+) I 1.5 2 GeV/C PION MOMENTUM Fig. 3- Elementary cross-sections for (TJ , K ) reactions feeding A and £ as a function of P(ir ), and schematic pictures of a resonant A hypernuclear state with large downward spin polarizatin and of a low lying hypernuclear state produced by compound decay of the resonant state. (GeV) -0.2 i k ' < \ s f N A (GeV) KAON MOMENTUM Fig. U. Elementary cross-sectin for the (K~, TT~) reaction feeding A> and a shematic picture showing a A hypernuclear level with a large downward polarizatin of the total spin and with an upward polarizatin of the total spin and with an upward polarization of the A spin. — 182 — polarizations and spin alignments are of vital importance for angular correlations to study electromagnetic moments and weak decay mechanisms. The (K~, Tf) reaction at P(K~)=1.5- 2 GeV/c has several unique features useful for spectroscopic studies of hypernuclei as shown in Fig. 4. The elementary process of the hyperon production is one or two orders of magnitude larger than that of the (if , K ) reaction. The momentum transfer is just adequate to populate directly'low-lying hypernuclear levels. They have large spin polarization and spin alignment. Furthermore the 1-5 Gev/c K~beam intensity is generally higher than the lower momentum K~ one. The spin (angular momentum) population of A-hypernuclear levels produced by the (ir , K ) and (K~, ir~) reactions are shown in Fig. 5. Hypernuclei with strangeness S=-2 are of great interest in views of possible existence of the strange dihyperon H, of double hyper nuclei, and of = 1. r rnuclei. Production of these hypernuclei (dihyperons) requires intense negative kaons (K~) with P(K)=1.5-2.2GeV/c because of the very small cross-section for the elementary process and of the very large momentum transfer. Experimentally they have been scarcely studied so far, and sevelal experimental programs are under progress. Recently we have studied double weak decays of two nucleons 2U in nuclei to the dyhyperon H with the mass Mg<2Mjj. The experimental data exclude the existence of the light H below 1875MeV. Identifications of the H and the hypernuclei with S=-2 require coincidence measurements of decaying particles with the (K~, K ) reaction. §6 Intensity Frontier Physics and International Collaboration Intensity frontier physics is a kind of big science projects in view of both facilities and physicists involved. There are several important frontiers with big science projects, which require huge costs and large person power. Therefore those -183 — (K-TI-) (7T+,K+) 0.2 0.1 " 0.0 5" 6 I 20S Relative population of A hypernuclear levels in J[Pb produced by the (TT + , K+) reaction at P(ir )=1 .05GeV/c and the (K-, TT~) reactin at P(K_)=1.6GeV/c. The momentum transfers involved in the (*+, K + ) and (K , *") A reactins are assumed to be Ai=in+lA and l=ln-1A. respictively. — 184 — projects have to be necessarily persuaded by international collaborations in such a way that a big facility A in a country a, and B in b, and so on, opening these big facilities internationally to users (physicists) in other countries as well as to domestic users. The nuclear physics committee in Japan has assigned the Japan Hadron Project (JHP) as the central nuclear physics facility in Japan. The first stage of the JHP aims at developing new frontiers of-physics with intense hadron beams, which can be provided by the intense 200uA 1GeV proton beam. The main accelerator is the high intensity iGeV linear accelerator .The secondary beams of kaons, pions, muons, neutrinos, neutrons, and unstable nuclei are used to study particle and nuclear physics and related physics. JHP is now being pushed by INS in collaboration with KEK and other universities. KAON proposed by TRIUMF aims mainly at developing new intensity frontiers of particle and nuclear physics by using intense KAON beams (Kaons, Antiprotons, Other hadrons and Neutrinos). They are provided by the 100^A 30GeV proton synclotron. Thus it is concerned with hadron probes such as intense kaons and antiprotons, which are produced efficiently by the higher energy primary protons, while JHP is concerned with the secondary particles such as pions, muons, neutrons, and exotic nuclei, which are produced by the lower energy primary protons, and with K, ir produced through the 12 GeV PS as well. In fact the major part of KAON had been included in the original plan of JHP. It has been assigned as the second stage program of JHP, which should be discussed later in consideration of possible plans in other countries. Consequently KAON is indeed complementary to JHP, and is just the plan which many of Japanese particle and nuclear physicists are interested in. Thus it is considered to be adequate to be promoted by international collaborations including Japan. TRIUMF is the nearest neighbor to Japan, except for Asian — 185 — countries, and the strong collaboration of particle and nuclear physics laboratories in Japan with TRIUMF is very important and fruitful. As the strong wind blows away leaves to find treasures, the intense beam clears up mists to find truth. As the warm sun makes one take off his overcoat, warm collaboration melts away locks to open treasury. Finally I wish to express my hearty thanks for all participants, especially those far (near) from Canada, and for TRIUMF, KEK, INS, Osaka Univ. and other laboratories for great contributions to this workshop. The author thanks Profs. H. Bando, T. kishimoto, N. Nagashima and many others for valuable discussions. Detailes are presented in this proceedings by individual authors. — 186 — CONCLUDING REMARKS Erich Vogt TRIUMF, 4004 Wtsbnok Mall, Vancouver, B.C., Canada V6T 2A3 ABSTRACT This workshop has covered in a very interesting and complete way the ba sic physics issues to be addressed by the complementary facilities, in Canada and Japan, intended to explore the intensity-frontier of strong-interaction physics. Japan has its new KEK facilities and its future Japanese Hadron Project (JHP): Canada has its present TRIUMF laboratory and its future KAON Factory. Both JHP and KAON appear very near to final construction approval. The possibilities are very great for new joint programs between the two countries which can lead the world in the new strong interaction physics. These concluding remarks describe the general science basis and particularly the models for the internationalization of science needed to make these new collaborations thrive. 1. INTRODUCTION This workshop has revealed the extraordinary elements which have now come together to enable Japan and Canada to jointly lead the world in the exploration of the new strong interaction physics. These elements are: • The new standard model of quarks, leptons and unified forces which has created very important new opportunities in subatomic physics including the topics addressed at this workshop: the physics of and in systems of coloured quarks intersecting through coloured gluon exchange (QCD). • The existing and about-to-be-completed kaon facilities at KEK. This work shop has revealed the strength of the Japanese physics community in the field and its extraordinary liveliness. • The prospects of the Japanese Hadron Project (JHP) and its many new arenas for physics. • The prospects of the Canadian KAON Factory at TRIUMF which will extend the KEK/JHP opportunities, and which is, in all respects, complementary to the facilities planned in Japan. • The tradition of strong collaboration established by Japanese scientists at Canada's TRIUMF, which can now lead to flow of scientists across the Pacific in both directions. • The important new emphasis of the Japanese government on the internation alization of science. Japan's science is ready for this. The large jets have brought Japan much closer to its industrialized partners. The location of TRIUMF, Van couver, Canada, is the natural gateway. The proximity of Tokyo and Vancouver is already discovered, every day, by thousands of Japanese skiers. — 187 — It is the combination of all of these circumstances - like a particularly auspicious planetary conjunction - which constitutes such a great opportunity for both na tions, 2. THE STANDARD MODEL AND THE WORLD NETWORK It has been very useful, at this workshop, to place the physics of JHP and KAON in the context of the standard model of quarks, leptons and unified forces. The standard model has brought about a startling change in all of subatomic physics. Not only has it provided a basis for the understanding of the wealth of data uncovered in particle physics and nuclear physics, but it has also raised many important new questions for the whole field; some of these are: • What are the properties of the new gauge bosons, Wi and Z°? • What governs the masses of the quarks and leptons? • How do systems of quarks behave? • How does one improve the standard model? Here, for example, one seeks greater unification, that is, to properly bring the strong force into the fold and thus achieve GUT; further, one seeks ways of hiding gauge symmetry which might be better than the Higgs or technicolour methods presently proposed, and one seeks to solve the hierarchy problems which arise when the vastly disparate masses of the different sets of gauge bosons {W±; X's, etc.) enter perturbatively into matrix elements. • How does one unify gravity with the other forces? • Why are there so many particles? Counting leptons, quarks (each in three colours), gauge bosons, Higgs particles, gluons, g's and gravitons, one has still an embarrassing richness of fundamental particles. • Is there a "theory of everything"? The new interests of particle physics are to search for improvements in the standard model and for what lies beyond it. The new interests of nuclear physics is to understand how, with QCD, one describes strongly interacting systems and how one uses such systems to study fundamental symmetries. This workshop has elucidated with particular clarity how the physics pur suits of the hadron facilities for the intensity frontier are complementary to, and go hand-in-hand with, the various other components of the whole world network of new major accelerator facilities. This network includes the new hadron-hadron colliders (e.g. the Tevatron, SPPS, etc.), the new ee" machines (TRISTAN, Bei jing, Cornell, etc.), the next generation of ee colliders (SLC and LEP), the future electron-proton collider (HERA), the proposed new supercolliders (UNK, LHC and SSC), the cw electron accelerator (CEBAF) under construction, the relativis- tic heavy-ion collider (RHIC) about to be funded, and of course, the intense hadron facilities, JHP and KAON. There are also many important new smaller projects. Altogether it is a world system of impressive proportions Unking together the -188 — industrialized nations of the northern hemisphere. People and ideas flow freely through the links. Almost all the action now takes place at these few large user facilities. As we have seen in the many talks of this workshop, JHP and KAON, taken together, address most of the important new issues. Their physics pertains, on the one hand, to the same high masses as the supercolliders. On the other hand it pertains to the hadronic and quark effects of the new facilities for nuclear physics. It is physics central to the whole field and of the highest priority. We must establish our bilateral links and get on with it. 3. INTERNATIONALIZATION In pursuing the new common interest of Japan and Canada in new joint activities at the intensity frontier, it is useful to understand the process in which appropriate internationalization is achieved. In order that all the participants of this workshop can be properly programmed to achieve our common goal, I take this opportunity to analyze the different models for internationalization and especially, below, to describe in some detail the workings of the "HERA MODEL" which Canada is using for KAON. A brief remark about the user mode and home-bases precedes this analysis. As mentioned above, the user mode is now rampant in subatomic physics. In every country the majority of particle physicists now travel some distance from their home institutions to carry out their experiments. Each country needs at least one home-base facility if it is to collaborate effectively at user facilities abroad. Such a home-base can be one of the major or less major components of the world net work. The Group of Seven (G7) nations (Japan, Canada, U.S.A., Britain, France, Germany, Italy) have their representatives in high-energy physics meet once a year as a working group to co-ordinate activities in this field. One of the earliest de cisions of the Working Group was to emphasize the need for home-base facilities. Home-base facilities do serve to bring economic benefits to the host country. Even more, they are vehicles for working effectively in facilities abroad. Thus TRISTAN serves Japan for its world activities in particle physics; the new KEK fixed-target facilities and JHP will serve Japanese medium-energy scientists as a staging base for work at KAON and elsewhere. For Canada, KAON will be the vehicle which takes Canadian scientists abroad, not only to KEK and JHP, but also to all the pieces of the world network. There are a variety of models for internationalization of big science projects, many of which have been developed with regard to large accelerator facilities. It is my view that basically three different models now apply. These are: A. The "CERN MODEL" is one in which a number of countries pool resources, usually through some appropriate formula, and jointly have legal and financial control. This model was pioneered by the European countries for CERN but has — 189- since also been used for European Spau Agency (ESDA), the European South- era Observatory (ESO), the French-British-German high-flex reactor at Grenoble (ILL), the large European fusion project (JET) and other science projects. B. The "NATIONAL PLUS MODEL" In this model (whose name we have invented) a single host nation dominates the science but invites other nations to participate. Because the host nation dominates, it usuaEy does not require commitments from foreign partners before making its own funding decision. There are many examples: the SSC project in the United States, the existing TRIUMF project in Canada, UNK in the USSR, KEK in Japan, Gran Sasso in Italy, etc. C. The "HERA MODEL" applies to projects which are intrinsically international - no nation dominates. It is an alternative to the CERN model. One nation hosts the facility, accepts legal and financial responsibility, but counts on foreign part ners for construction contributions. The "HERA MODEL" was pioneered by West Germany for its HERA project. It involves rather formal steps which we describe separately in a more complete description of the HERA model. Because the host nation does not dominate the science of the facility, it requires a clear statement of intent from its foreign partners before it makes a final funding decision. The "HERA MODEL" probably works only for cases in which the host nation's share of the science lies between 25 and 50%. If more than 50%, it would likely choose the "National Plus" route. If less than 25%, it would likely seek to follow the "CERN MODEL". 4. COMMENTS ON THE HERA MODEL I would like to give here a more detailed description of some aspects of the HERA model, which is less familiar to most of us. It was developed by Germany for the funding of its HERA Facility, and can now be regarded for many medium-sized countries, including Canada and Japan, as the standard model for the internation alization of large accelerator facilities. The basic features and key ingredients of the HERA model are given above. The facility is hosted by a single country with a minority interest in science, but with other countries participating in the funding and serving on all the advisory boards of the facility. The immediate paradox about the HERA model is that it should work at all. Why would any country want to host a facility in which it has a minority interest in the science, and secondly, why would participating countries want to pay for something that they might get free? Increasingly, for science facilities, independent of the model under which they are operated, proposals are accepted on the basis of scientific merit only, and not on whether or not the country pays its dues. These questions have rational answers. For the host country, there are a number of factors which offset its major fi nancial commitment. It can choose to expand on its existing excellence, as Canada is doing when it bases its KAON factory on TRIUMF. It benefits greatly from the — 190 — inflow of people and ideas and spin-offs. Every country wishing to participate in the work of the international network of large accelerator facilities, benefits greatly from having a home-base facility through which that work flows. A country which hosts a large facility on the HERA model, even though it has a minority interest in the science, benefits enormously from all of the ideas pouring out from the entire world network. Finally, direct involvement of foreign nations through participa tion in the funding of the facility is the best manifestation of all of international approval of the facility, and acts therefore as a funding catalyst. For the participating countries, who have to pay for something that they might think of getting for free, it should be noted first that the contributions are not cash, they are in high technology components, which have impact on high technology at home. Above all, there is the rationalization of internal plans and priorities. Most countries cannot dream now of having a balanced set of large accel erator facilities at home. They must make choices, they must build on excellence, yet most countries have scientists interested in the entire span of ideas. Each coun try must make critical choices by participating with other countries in funding. A country participating in the HERA Model process has a very cost-effective way of satisfying the needs of its scientists in that field and then getting on with its own home-base facility. It is not altruism on a national scale, but pragmatic judgment which makes the HERA model work so effectively. There are a number of formal steps associated with the HERA Model. These steps taken in total make it an incredibly effective self-seduction sequence for countries seeking to establish a major science facility. The five steps are: (i) The host country has an interesting idea for big science facility and pre pares a proposal. Canada did this for its KAON Facility, in September 1985. (ii) The host country makes an initial exploration abroad of foreign interest in its facility. Canada did this for KAON in November and December 1987, and found very strong interest abroad. In its exploration of foreign interest in KAON, a year ago, Canada visited Washington, Tokyo, Bonn, Rome and London. This yielded widespread support for such a Canadian facility. It was viewed as not only excellent physics but also the opportunity for Canada to become a major player in particle physics. The foreign nations encouraged Canada to make a commitment to KAON of sufficient magnitude to initiate the round of consultations now taking place. In May 1988, the Working Group in High-Energy Physics of the G7 countries again encouraged Canada and defined the step now needed for Canada to be taken seriously. The following extract from the minutes of that Vancouver meeting are self-explanatory: "Canada reported on progress since last year on its proposal to build a KAON Factory at TRIUMF. International collaboration on construction funding has been explored with encouraging results, and a decision by Ottawa — 191 — appears near on the final Project Definition Studies ($11M) including negotiations with foreign partners. The Working Group reaffirmed last year's conclusion that there is a very good scientific case for a machine of this type for the sound devel opment of high-energy physics. It also concluded that an early decision by Canada to proceed with its KAON Factory would be very welcome and it encouraged Canada to seek interest and engagement from the international community. It was noted that other projects, such as the Japanese Hadron Facility, would explore interesting fields complementary to the KAON Factory." In July 1988 Canada funded the Project Definition Study and the envisaged consultations are under way. In the first round of visits the Canadian delegation will now travel to: Rome (April 17), Bonn (April 19), London (April 21), Paris (April 24), Washington (May 9) and Tokyo (May 17). Separately from the formal visits of the Canadian delegation, TRIUMF scientists are very active in engaging the interests of foreign scientists in the KAON Factory. The Canadian Project Definition Study followed in July of 1988. (iii) The host country having explored abroad declares it serious intention about the matter. This statement of intention for creating the KAON Factory was the Project Definition Study of July 1988. (iv) The host country formally consults abroad, intending to achieve some thing close to letters of intent before it makes its own final commitment. Canada is now in the process of doing this for KAON. (v) The host country makes its decision and then completes its agreements with its foreign partners. 5. APPLICATION OF THE HERA MODEL TO THE CANADIAN KAON FACTORY For Canada's KAON Factory, it is estimated (below) that Canadian scientists will constitute about a third of the total user community of 800 scientists. Canada is clearly in a minority position. The special contributions of foreign partners oc cur in the construction phase. In the operating phase it is assumed that the host country, Canada, will assume the full normal operating costs - estimated to total about $90M (Canadian) per annum — which apply to accelerator maintenance and electric power and other similar costs. In the operating phase, the foreign partners pay the normal proportion of jointly funded detectors and experimental equipment according to the well-established custom which now prevails for all facilities inter nationalized under the CERN MODEL, the NATIONAL PLUS MODEL, or the HERA MODEL. The arguments here, then, pertain to the special contributions to accelerator construction relevant to the HERA MODEL. The total proposed level of foreign contributions to initial construction, in the HERA MODEL, is quite naturally about a third of the total construction cost. The civil components (buildings, tunnels, much of the shielding, etc.) are -192- more easily assigned to the construction firms near the site of the facility, and are therefore domestic. The two-thirds for accelerators and beam lines are the attractive high-technology pieces. The host country clearly wants a major share of this portion to stimulate the domestic economy, and therefore ends up offering about half of it to foreign partners. So it is for Canada's KAON Factory. The total construction package for KAON is $571M (1987 Canadian dollars). The foreign participants are anticipated to have two-thirds of the science action, and it is proposed that they contribute accelerator components worth one-third of the total construction costs. The proportion proposed for each country is based on our estimate of the fraction of the 800 scientific users of the KAON Factory expected to originate from that country. It takes account of the site of each country's medium-energy physics community, of the convenience of the Vancouver location for the community, and of any special interest in the KAON Factory expressed by the scientists of the community. In its first round of consultations for participation in the KAON Factory, in the spring of 19S9, Canada is directly approaching its partners among the Group of Seven (G7) nations. It is here that the main foreign partners are anticipated, and where the main competitors for our KAON Factory plans existed. Based on the above general principles, we present the following table for the proposed level of participation in Canada's KAON Factory: Estimated % Proposed level Country of KAON users" of participation (Canadian S) Canada 30-35 400 Mb United States 30-40 90 M Japan 8-10 50 M Germany 6-8 30 M Italy 5-7 30 M Britain 1-3 C France 1-3 c Other 8-15 "Total number of users estimated to be about 800. includes S90 M already committed by the Province of B.C. cAmount to be proposed during consultations. The situation in various countries at the time of this workshop is as follows: -193 — Japan The Japanese Hadron Project (intense beams of 1 GeV protons with many added arenas for new physics) is entirely complementary to KAON and appears to be far along on its road toward funding. The ties between the Japanese medium- energy community and the corresponding Canadian community are warm. In ad dition to this joint JHP-KAON workshop, a hypernuclear workshop for KAON will be held at Tsukuba in June 19S9. Germany Fifteen months ago the German medium-energy physics community was ac tively pursuing the European Hadron Facility (EHF). The community itself de cided, on December 15, 19S7, to push participation in Canada's KAON instead. Also, in May 19S8 the Specht Committee reported tc the German government as follows: "The physics perspective of a hadron facility was viewed as important and interesting. In first priority the Federal Republic shall participate in the planned KAON Factory at TRIUMF in Vancouver, Canada. German experimental groups for KAON shall be supported appropriately under the aegis of Federal Research Funds. Participation in the construction of a European Hadron Facility EHF (with a 100 /zA beam intensity) is not recommended. In case KAON is not realized the possibility of a more modest European solution at CERN (with about 10 ^A beam intensity) shall be discussed anew." Germany has appointed an agency (Kernforschungsanlage Jiilich) and a rep resentative (Professor J. Treusch, Deputy Director of KFA Jiilich) to work with Canada in establishing Germany's participation in the KAON Factory. A KAON workshop will be held in Bad Honnef in early June. Canada has been a strong partner in HERA and a correspondingly strong German participation in KAON appears to be emerging. Italy Italian scientists have been especially strong proponents of EHF and only very recently have begun consideration of a complementary facility in Italy instead. Because of Italy's very important role not only here but across the board in particle physics, it would be very natural for Italy to play a major role in the KAON Factory despite the distance. The level of participation in construction depends on the level of involvement of the Italian medium-energy physicists which is only now beginning. Britain Involvement of Britain in KAON along the lines of its involvement in HERA appears likely. -194 — France French scientists played only a minor role in EHF, but France has been a leader in particle physics and nuclear physics. It has plans of its own in medium- energy physics. Some scientific interest in KAON is evident and therefore some French involvement is likely. Other Many countries other than Canada's G7 partners have expressed interest in KAON and are likely to contribute some components and certainly some scientists. 6. CONCLUSIONS It is up to us, the participants of this excellent workshop, to accomplish the joint programs of KEK/JHP and KAON discussed here in the past two days. Inter nationalization is carried out by scientists, not by governments. Government's role is to facilitate the necessary arrangements. We are fortunate to have governments which seem to be prepared to carry out our bilateral arrangements. On both sides we need to get on with the necessary joint programs of the intensity frontier. Japanese scientists from institutions across the country have the opportunity to exploit the new KEK facilities, to establish JHP and to begin now to think of complementary programs based in both JHP and KAON. It is the combination of the transpacific opportunities which will be attractive to scientists and graduate students alike. Canadian medium-energy scientists believe they are already building KAON (the Canadian government should share this conviction next year) and are intensely involved in planning for it. However, with TRJUMF as a base, they must exploit the new KEK facilities, and also actively pursue future JHP opportunities. The pipeline of people and ideas must flow across the Pacific in both directions. For the physics at the intensity frontier, we will have a new world map whose main centres, Tsukuba and Vancouver, are on the Pacific and whose greatest link crosses the Pacific to join these two centres. The very strong intellectual activity manifested at this meeting will be the driving force of this link for the next two decades. Let's get on with the job and our governments will follow. -195 —