COLORSUPERCONDUCTIVITY, INSTANTONS AND PARITY (NoN?)-CON ERVATION AT HIGHBARYON DENSITY
November 11,1997
Organizer Miklos Gyulassy
Building 510, Brookhaven National Laboratory, Upton, NY 11973, USA Other RIKEN BNL Research Center Proceedings Volumes:
Volume 1 - Open Standards for Cascade Models for RHIC - BNL-64722 June 23-27,1997 - Organizer - Miklos Gyulassy
Volume 2 - Perturhtive QCD as a Probe of Hadron Structure - BNL-64723 July 1425, 1997 - Organizers Robert Jaf€e and George Stermaa
Volume 3 - Hadron Spin-Flip at RHIC Energies - BNL-64724 July 21 - August 22, 1997 - Organizers T.L. Trueman and Elliot Leader
Volume 4 - Inauguration Ceremony, September 22 and Non-Equilibrium Many Body Dynamics - BNL-64912 September 23-25, 1997, Organizer: M. Gyulksy
J
I Preface to the Series
The RIKEN BNL Research Center was established this April at Brookhaven National Laboratory. It is funded by the “Rikagaku Kenkysho” (institute of Physical and Chemical Research) of Japan. The Center is dedicated to the study of strong interactions, including hard QCD/spin physics, lattice QCD and RHIC physics through nurturing of a new generation of young physicists. For the first year7 the Center will have only a Theory Group, with an Experimental Group to be structured later. ’heTheory Group will consist of about 12-15 Postdocs and Fellows, and plans to have an active Visiting Scientist program. A 0.6 teraflop parallel processor will be completed at the Center by the end of this year. In addition, the Center organizes workshops centered on specific problems in strong interactions. Each workshop speaker is encouraged to select a few of the most important transparencies from his or her presentation, accompanied by a page of explanation. This material is collected at the end of the workshop by the organizer to form a proceedings, which can therefore be available within a short time.
T.D. Lee July 4, 1997
c
1 V CONTENTS
Preface to the Series ...... 1 List of Participants ...... 111 Introduction Miklos Gyulassy ...... I QCD at Finite Baryon Density: Nucleon Droplets and Color Supercon- ductivity Krishna Rajagopal ...... 3 Color Superconductivity at High Density Mark Akford ...... 25 Instantons and Color Superconductivity Thomas Schtife...... 41 Test of Discrete Symmetries in Relativistic Heavy Ion Collisions YangPang...... 77 Parity N.P.Samios ...... 91 Experiments at the AGS Brian Cole ...... 119 Agenda ...... 139 Participant List Workshop on Color Superconductivity, Instantons and Parity (Non?)-Conservation at High Baryon Density 11 Novemberber 1997
Mark Alford Anthony J. Baltz Jiirgen Bergs Institute for Advanced Study Physics Department Department of Physics Olden Lane Brookhaven National Laboratory MIT Princeton NJ 08540 Upton, NY 11973-5000 Cambridge, MA 02139
Tom Blum Brian Cole Michael Creutz Physics Department Department of Physics Physics Department Brookhaven National Laboratory Columbia University Brookhaven National Laboratory Upton, NY 11973-5000 New York, NY 10027 Upton, NY 11973-5000
Hirotsugu Fuji Xiaofeng Guo Miklos Gyulassy (ORG) RIKEN BNL Research Center Department of Physics Department of Physics- MS 5202 Bldg. 510 Columbia University Columbia Unjversity.,
Upton, NY 11973-5000 New York, NY 10027 550 W 120th St. . I * New York, NY 10027
M.W.Hd&z Hiroyoshi Hiejima Bob Jaf€e Department of Physics Columbia University Department of Physics S,UNY/Stony Brook Nevis Labs MIT Stony Brook, NY 11794 POBOX137 ’ Cambridge, MA 02139 Irvington, NY 10533 and RIKEN BNL Research Center
Dmitri Kharceev Ken Kim Klaus Kinder-Geiger RIKEN BNL Research Center Department of Physics Department of Physics Building 510 Brookhaven National Laboratory Brookhaven National Laboratory Upton, NY 11973-5000 Upton, NY 11973-5000 Upton, NY 11973-5000
John M~ch-R~ssell Dens Molnar Shigemi Ohta Institute for Advanced Study Department of Physics KEK and Olden Lane Columbia University WEN BNL Research Center Princeton NJ 08540 New York, NY 10027 Building 510 Upton, NY 11973-5000
James Osborn Yang Pang Rob Pisarski Department of Physics Department of Physics, Box 16 Physics Department SUNY/Stony Brook Columbia Uqiversity Brookhaven National Laboratory Stony Brook, NY 1’1794 New York, NY 10027 Upton, NY 11973-5000 and Brookhaven National Lab.
iii Jianwei Qiu Krishna Rajagopal Dirk Rischke iV Iowa State University and Department of Physics REEN BNL Besearch Center Department of Physics MIT 6-3088 Building 510 Brookhaven National Laboratory Cambridge, MA 02139 Upton, NY 11973-5000 Upton, NY 11973-5000
N.P. Samios Thomas SchZer Dam Son Physics Department I Inet. for Nudear Theory Department of Physics Bsookhaven National Laboratory University of Washington MIT 6-308A Upton, NY 11973-5000 Seattle, WA 989195 Cambridge, M;I 02139
Misha Stephanov Larry Trueman Michel Tytgat Dept. of Physics & Astronomy Physics Department Physics Department SUNY/Stony Brook Brookhaven National Laboratory Brookhaven National Laboratory Stony Brook, NY 11794 Upton, NY 11973-5000 Upton, NY 11973-5000
Stephen E. Vance Momchil Velkovsky Jac Verbaarschat Department of Physics Department of Physics Department of Physics Columbia University Brookhaven National Laboratory. SUNY/Stony Brook 538 W 120th St. Upton, NY 11973 Stony Brook NY,Il?943800 New York, NY 10027
Rank Wilczek Dave Winter Xihong Yang InstitKte for Advanced Study Department of Physics Nevis Laboratories ,Olden Lane Columbia University P 0 BOX 137 'Princeton NJ 08540 New York, NY 10027 Irvington, NY 10533
Ismail Zahed Bin Zhang Department of Physics Department of Physics SUNY/Stony Brook Mail Code 9334 Stony Brook NY 11794-3800 Columbia University New York, NY 10027 Color Super-conductivity, Instantons, and Discrete Symmetry Breaking at High Baryon Density
This one day Riken BNL Research Center workshop was organized to follow-up on the rapidly developing theoretical work on color super-conductivity, instanton dynamics, and possible signatures of parity violation in strong interactions that was stimulated by the talk of Frank Wilczek during the Riken BNL September Symposium. The workshop was held on November 11, 1997 at the center with over 30 participants. The program consisted of four talks on theory in the morning followed by two talks in the afternoon by experimentalists and open discussion. Krishna Rajagopal (MIT) first re- viewed the status of the chiral condensate calculations at high baryon density within the instanton model and the percolation transition at moderate den- sities restoring chiral symmetry. Mark Alford (Princeton) then discussed the nature of the novel color super-conducting diquark condensates. The main result was that the largest gap on the order of 100 MeV was found for the O+ condensate, with only a tiny gap << MeV for the other possible 1+. Thomas Schaefer (INT) gave a complete overview of the instanton effects on cor- relators and showed independent calculations in collaboration with Shuryak (SUNY) and Velkovsky (BNL) confirming the updated results of the Wilczek group (Princeton, MIT). Yang Pang (Columbia) addressed the general ques- tion of how breaking of discrete symmetries by any condensate with suitable quantum numbers could be searched for experimentally especially at the AGS through longitudinal A polarization measurements. Nicholas Samios (BNL) reviewed the history of measurements on A polarization and suggested spe- cific kinematical variables for such analysis. Brian Cole (Columbia) showed recent E910 measurements of A production at the AGS in nuclear collisions and focused on the systematic biases that must be considered when looking for small symmetry breaking effects. Lively discussions led by Robert JaEe (MIT) focused especially on speculations on the still unknown signatures of O+ color super-conductivity which of course would not be observable via discrete symmetry breaking. Thanks to Brookhaven National Laboratory and to the U.S. Department of Energy for providing the facilities to hold this Workshop. Y Miklos Gyulassy (Organizer)
1 QCD at Finite Baryon Density: Nucleon Droplets andcolor Superconductivity
Mark Alfordl, Krishna Rajagopa12 and Frank Wilczekl
'Institute for Advanced Study, School of Natural Sciences Olden Lane, Princeton, NJ 08540
2Center for Theoretical Physics Laboratory for Nuclear Science and Department of Physics Massachusetts Institute of Technology, Cambridge, MA 02139
We use a variational procedure to study finite density QCD in an approximation in which the interaction between quarks is modelled by that induced by instantons. We find that any uniform state of nonzero density with conventional chiral symmetry breaking has negative pressure with respect to empty space, and is therefore unstable. This is a precisely defined phenomenon which motivates the basic picture of hadrons assumed in the MIT bag model, with nucleons as droplets of chiral symmetry restored phase. At all densities high enough that the chirally symmetric phase fills space, we find that color symmetry is broken by the formation of a (44) condensate of quark Cooper pairs. A plausible ordering scheme leads to a substantial gap in a Lorentz scalar channel involving quarks of two colors, and a much smaller gap in an axial vector channel involving quarks of the third color.
J
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$- no 24 .
Color Su percond uctivity at h igh density
M. Alford (IAS)
K. Rajagopal (MIT)
F. Wilczek (IAS)
25 I The Lorentz scalar colored condensate Gap, equation of state, gauge symmetries
I1 The axial vector colored condensate exotic but fragile
I11 Future Directions 27
* At high enough density, attractive quark-quark interactions in QCD should cause condensation of Cooper pairs (diquarks). In our model, the instanton vertex provides an attractive interaction, and a colored diquark condensate forms.
1- (U"CY5dP)&aPQr-0 Lorentz scalar, color 3. Robust.
Gap N 100 MeV
Lorentz axial vector, color 6. Sensitive.
Gap N 1 keV 28
Comparing Chiral and Colored condensates x
I. Lorentz scalar colored condensate The ansatz:
IF(pp)) is the Fermi sea filled up to momentum pp. This state is antisymmetric in color, flavor, and spin. It selects the color 3 direction. Minimizing E - pN with respect to the O(p), we get the gap t equation. The gap equation is
..
Note BCS divergence as A + 0: there is always a solution, for any interaction strength K and chemical potential p. 31 Co1w gap vs chemical potential (GeV), A = 700 MeV.
0.15
0.125
0.1
0.075
0.05
0.025
;e 0.2 0.4 0.6 0.8 1 ? ' p=o
A Maximum gap is N 100 MeV, smallu than for chiral at p '=: 0 but same order of magnitude.
0 It is suppressed by phase space (small Fermi surface) as p + 0, and by asymptotic freedom (decoupling of the vertex) at large p.
0 Robust vs changes in A 32
0. 2
0.17 5
0.1 5 0.12 5 0. 1 0.07 5
0.0 5
0.02 5
1 0.2 0.4 0.6 0.8 1 33
Density with SC condensate compared to free quarks, A = 700 MeV.
2:
1.75:
1.5: 1.25:
1:
0.75;
0.5;.
0.25:
I 0.2 0.4 0.6 0.8 .1
The superconducting condensate has little effect on the equation of state. 34
Gauge symmetries
Long-range interactions are affected by the condensate. 1 Instead of color and electromagnetism (9 massless gauge bosons) we have a reduced color group and a rotated electromagnetism (4 massless gauge bosons)
quark Q' charge
I. dred,green 2 Ublue 1
dblue 0 Axial condensate 36
log(Axia1 vector gap) vs chemical potential (GeV).
\
As before, the.BCS singularity at the Fermi surface guarantees a solution, but only one color participates, and not all p fully participate, so the gap turns out to be very small and sensitive to the cutoff. No robust prediction is possible. Other interactions may push it up or down. 37
Summary of Condensates
Chiral sc Ax
1 6 1 1 1 3 1 1 1 @/3 SpinP O+ O+ I+
Gauge sym Q=$(B+L) Gauge bosons 8+1=9 3+1=4 3 Massive G.B. 0 5 6 38
* Conclusions
0 High-density state is not a Coulomb phase of free quarks and gluons, but is broken down to SU(2)/;c- U(1)~j. This
i can be described as a Higgs or a confined phase: Confinement without chiral symmetry breaking.
We have not yet found a signature of these condensates for heavy ion collisions. With’ a bigger gap, axial vector condensate would give striking polarization correlations.
Neutron stars may be sensitive to condensates. E.g., a gap will slow down cooling by neutrino emission. 39 The Future 40
e Finite temperature. What is T,(p)? (Expect N A)
.eStrange quark: Six leg instanton vertex
- new possibilities, eg (qiaq&i%apB breaking to diagonal of color and flavor.
- explore m, dependence. - condensate will have to break flavor as well as color, hence local order parameter.
a other interactions: gluons, electromagnetism, effective in teract ions .
e 0t her condensates
0 Details of non-uniform chiral breaking phase: droplet size, percolation-d riven restoration of chira 1 symmetry.
e Consequences for neutron stars (coohg.. .>
e Consequences for heavy ion collisions (screening of broken gauge fields in quark-gluon plasma?). Instantons and Color Superconductivity
T. Schafer
Institute for Nuclear Theory, Department of Physics, University of Washington, Seattle, WA
98195
Abstract
Instantons lead to strong correlations between up and down quarks with
spin zero and anti-symmetric color wave functions. In cold and dense matter,
nb > n, N 1f m-3 and T < T, N 50MeV, these pairs Bose-condense, replacing
the usual (i&) condensate and restoring chiral symmetry. At high density, -i the ground state is a color superconductor in which diquarks play the role
of Cooper pairs. An interesting toy model is provided by QCD with two
colors: it has a particle-anti-particle symmetry which relates (@) and (44)
condensates.'
41 42
Collider ] T--,----- T E-afew GeVfim3 43 , ...... 45 46
...... a ., .. - ' r...... 48 '. . ' ..* ......
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d d d d d U 49
.. 50
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1
0.5
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0.5
0 0 0.5 1 1.5 57 ,~..:. . , , ...... ~ .... . - ... ..
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1
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. .. ..
62 63
0.1 0
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I , , , , I I -.I ??-I- 0.00 0.0 0.5 1.o 1.5 2.0 2.5 3.03 64 ,, 65
I O / /' -I 1000.0 - \/NO I 0 __------_-_ i _-/n
n 66 67
4
-2
FIG. 1. 68 69
1.2
1
0.8 A wcp "\ 0.6 A U IU - 0.4 o.2 1- -CJ- - m=30 MeV - .----)c--.. m=40 MeV Ot""""""""'~' 0. 0.5 1 1.5 2 cLEfm-'I
0 0.5 1 1.5 2 cLEfm-'I
FIG. 5.
... 70
100
10 cb
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0.1
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1
0.1 . ., 71
10 10
1 vl 1 Ern En 0.1 0.1
0.01 0.01 0 0.5 1 1.5 7CfmI
10 10 1 *. nv 1 > €- i I E" 0.1 0.1 0.01 0:Ol 0.001 ' 0.001 0 0.5 1 1.5 0 0.5 1 I .5 7[fmI TCfm3 0.6
0.4 ma
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I I I I 1 I I 1 1 I I I -
......
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0 0.2 0.4 - 0.6 0.8 1 2 4' 6 .. Afm-lI E.L[fm-'I .. 75 ., . .
..
FIG. 9. 76
5'0 0 0
4000 - -I n3000 -I L I v c i 2000
1000
0 0 5 10 15 20 25 P
5000
4000
3000 n so00 r= 1000
0 0 5 10 15 20 25 P
3- lc$ Test of Discrete Symmetries in Relativistic Heavy Ion Collisions
Miklos Gyulassy’, T.D. Lee’ and Yang lDepartment of Physics, Columbia University, New Yo&, NY 10027 and Department of Physics, Brookhaven National Laboratory, Upton, NY 11973
For matters at high baryon densities, such as those created in relativistic heavy ion colli- sions at BNL-AGS, it has recently been shown by M. Alford, K. Rajagopal, and F. Wilczek [l],and also independently by R. Rapp, T. Schafer, E.V. Shuryak, and M. Velkovsky [2], that interesting condensates could be formed. The possibility for detecting the existence of some condensates from parity violation measurements was also suggested [3, 41. Several explicit models [5] were constructed by T.D. Lee for studying the formation of condensates that spontaneously break the discrete symmetries. These models could provide a basic framework for testing discrete symmetries in relativistic heavy ion collisions. The longitudinal polarizations of A’s and A’s &e very effective in detecting parity vio- lating condensates. The large number of A’s produced in relativistic heavy ion collisions at BNL-AGS, CERN-SPS and BNL-RHIC, suggests it is possible to make an accurate determi- nation of the existence or absence of any parity violating condensates. Several experiments at BNL-AGS are capable of this type of measurement [6, 71. The background for longitudinal polarization of A’s is dominated by decay to A. In fact, it was first suggested by M. Jacob to use the longitudinal polarization of A7s and A’s as an indirect measurement of E/A and g/A ratios under the assumption that parity is conserved in heavy ion collisions [8]. References:
[l] M. Alford, K. Rajagopal, and F. Wilczek, hep-ph/9711395. [2] R. Rapp, T. Schafer, E.V. Shuryak, and M. Velkovsky, hep-ph/9711396.
[3] F. Wilczek, in Proceedings of RIKEN BNL Research Center Symposium on Non-Equilibrium Many Body Dynamics, Volume 4 (1997). [4] F. Wilczek and K. Rajagopal, private communications. [5] T.D. Lee, Phys. Rep. 9C, (1974). [6] N. Samios, in this proceedings. [7] B. Cole, in this proceedings. [8] M. Jacob, Z. Phys. C38, 273 (1988). 78
,
Test of Discrete Symmetries in Relativistic Heavy Ion Collisions
r' Miklos Gyulassy, T.D. Lee and Yang Pang
RIKEN BNL Research Center Workshop on Color Superconductivity, Instantons, and Parity (Non?)-Conservation at High Baryon Density
November '11. 1997 79
I.
Outiine
0 Spontaneous Breaking of Discrete Symmetries
0 Observables from High Baryon Density
Test of Discrete Symmetries 80
Spontaneous Breaking of T invariance
Model Lagrangian
L T.D. Lee, Physic Report 9C,(1974) where U(+) = &(d2 - p2)2
-P P
C invariant under C, P and T Vacuum expectation value < Q >vat= p > 0 +-.P+S@
C violates T,P, and CP
T violating amplitude Spontaneous Breaking of P invariance
A,: Axial vector or a& with
C Breaks P and C 83
Pseudo-Scalar in PDG
Name Mass (MeV) I G (JPC )
140 1-(0-+) 547 o+(o-+j ‘I! 957 o+(o-+)
Axial-Vector in PDG
Name Mass (MeV) IG(JPC)
UI(1260) 1230 1-( I++) fi(126O) 1285 0+(1++) e.. Condensates from high temperature and high baryon densities
Many things to choose from: Nucleon currents qrT$ Quark and diquark currents
, Meson currents Gluons
For example:
gluon + diquark (1+) could form 0-- Disoriented ChiraI Condensate: 0-+ 85 1.3. Schlagel, et al.
Au + Au at 11.7 Gevk '- '- -Si + Au at 14.6 GeVk 0.8 e--a Si + Si at 14.6 GeV/c
0.6
0.4
0.2
0.0 I 0.0 2.0 4.0 6.0 8.0 10.0 12.0 86
c 16.0 *
2 Reflected Ooio Data 14.0 - _---. t i . I ! ! ! \ , ! 12.0 t '\ARC prediction I I \ ! , +i 10.0 t1 I 1 ! 1 + 8.0 +! i I I
6.0 * Ai : ! i f 1 ! 4.0 i: t I 1 I ! i i I 5 i 2.0 Clz-/ .' -. ?- L 0.0 * 0-0 0-4 0-9 1.2 1.6 2.0 2.1 2.6 3.2 Ra pidit y 87
Decay of A with a definite helicity
.-, MA+T-p = a, t
Decay of A with polarization
1
,For spontaneous breaking of P in heavy ion collisions
A given event has fixed polarization: p
Average of @'over events = 0 88 A Production in A+B HIJING--
... I. .. ..a .. I" I .i 1 1 NA49 PbPb 158 AGeV
-I Pb+Pb 11 AGeV -
b4fm A
nn u-u 0.0 1 .o 2.0 3.0 .4.0 5.0 6.0 Lab Rapidity y AA Correlation 89
0.3
60 0. a2
49. a/ 90
4
Conclusions:
Test of c lscrete symmetries is a valuable tool for probing the existence of certain condensates, independent of any specific model
Lambda polarization could be used to test parity violation from relativistic heavy ion co I I isio ns
. Parity
N.P. SAMIOS Brookhaven National Laboratory Upton, New York 11973
Previous investigations of possible parity violations in strong and weak interactions is reviewed. The now classic studies of A' produced in T-p interactions is discussed. Parity violation in A' decay (i.e. in weak interaction) was observed via an updown asymmetry, that is with respect to the production plane defined by j,- x jAo. If parity is violated in the strong interaction, that would give rise to asymmetries in the production plane, categorized by a front-back or left-right asymmetry. No such effects were found in A' production. Similar studies can be carried out for A' production in Gold-Gold reactions. In this case one can look for a parity violating effect in strong interactions via asymmetries in the production plane defined by jAux jA. It would also be interesting to look for parity violation in the weak interaction in A' produced by AuAu interactions. Such possibilities for various AGS experiments were also discussed.
91 92 93
f"
'..
. 94 95
A A
I/ I
a-
%+?E +- 96 97
B'
--
9 98
-m t.O.--~--. .... ( .e - .,. -6 . ...
..I I. rn .2 . 0. v) (1 0 u -.z . - . -.1 '.F . -.e 1.0.- I , 9 40
**. 8. a. 0- u -0 I - .. 1' -.?. - --- 0 -.4 --t -...... g -.a ...... I -.. 4- . -- *.: .... i' -1.0 A- --.I .___.I .. __ 4 I. _.._I .... I... I 0 40 00 IZF 180 200 ?..lo ?.e0 310 360 DEGREES
FIG.10. Angular correlatiou plot for tlic icxtiml F-+p-+An+,p, G"~-tr+t-r-.The0 varinlion extends from x/2 to T sinm (Ice r+ad x- are indistinguishable iii this experiiiicnl.
*. -I-- -7.- ...... __ . --......
...... 0 ...... - ._-_
> 120
FIG.9. Angcilnr coriclnlion plot for the reaclion r--l-fi+Ao+?", .---- h"-+r---l-p. *'We wish here to acl:trowIctigc soiiie very Iielphl discussions with I). Lee on tliese qiicstions, and R coomniuiiication fronl Knrplus.T. K. _- .
99
M
0 cv m
0 Q cv
-
0 m
10 1
2 I, 17 '1' 'I' 17 11 s 'I' 0
v)
W U 0
m =#
* -1.0 0 t 1.0 COS 0
l;i(:. 1. 1)istriIiiitioii iii cod lor iiroccss (1). llic slindcd arca 102 -.) A ‘, 4 \
lab cm. FIG. 2. h¶nemon& (nonr_elativietic)dlngram in velocity space. T, A. and A are unlt vectors, refer- ring to the direction of the incident T uith respect to the center of mass, the A with regard to the labora- tory frame, and the A with regard to the c. m., all ae seen in the A rest frame. See d80 reference 9.
may be written M.E. = a+ bcose + icsinO~*~+di?*~, FIG. 1. Magnitude of the A deca aeymmetry in the where d the parity-nonconserving amplitude. production plane, minus [3~/m(e)l, the mean value is 9 Then, in the “r - c.m.” coordinate system expected from statistical fluctuations alone, plotted (Fig. versus 0, the c. m. production -le. The 2 and Table I), we have _c_ hyperon plott? errors are the rma fluctuatioas *[ (21/2)3/ I(e)p,(e) = 21mc* (a + bcos e) she,
N(O)I ’ I(e)p,(o) = 2 Red*(a + &cose), I(e)p,(e) = zRed*c tems might be expected to be “‘preferred” in the sine, sense that the polarization in the production r(e) = ia + ~COS~I~+I csineIa+ idla. plane not sancel vectorially averaging would in After averaging over 8 have over 0. we The results are summarized in Table L No (I$) = (rh)Imc*a, (31 statistically significant average polarization in (IP,) = 2 Red*a, (4) the production plane is apparent in any of the coordinate systems.“ (This result was, of (IPS) = (a/2) Red*c, (5) course, guaranteed by the negative result from 7 = lala+ lbIa/3+21 ciZ/3. (6) the preceding “coordinate-invariant” analysis.) We now adopt the hypothesis that parity is not Since P, is observed to be large, c and a must conserved in production in order to determine both be nonzero, and their phase difference can- an upper limit to the puity-noncoascn@ am- not be 0” or 180”. Therefore, Pf.ad Pa cannot plitude. In the notation of Drell ad Lee -both vanish, unless Id1 is 0. --et ai., the production matrix elementat.’ (WE.) If ve eliminate the phase of d from Eqs. (31,
Table I. Polarization 0o-t~ averaged Over hyperon c.m. production angle. Here is-a unit vector in fw directioa P(r irrcldent) x F(hyperon): Tbe standard dcrlatAom 011 dl QP,,~,,are (3/236) =0.113. Prub. (x,,r z)=ucp{ -[a2 4 z+azP2z1236/6}=thz ppbablMYtst of getting a x2 M large as or larger than that observed. if the true values are P,=P2=@.
coord. MS Ma his - system No. 3 No. 1 No. 2 & Qpt 4 PIdJ. (x,,2 t - A- c.m n - ‘i Xj 0.55 -0.13 +‘0.15 0.21 - - + h-c.m. -n a. n xx 0.55 0.087 + 0.068 0.62 A -lab n A i x: 0.55 -0.046 +0.18 0.26
211 ecay to the first excited state of is pre- plane. We ma~repart our analysis of 185 events ominantly G-T since, if one accepts the Fermi of the same type, but produced at a higher ener- ransition as vector,* any admixture d a Fermi gy by piona of 1.23 Bev/c, leading to 375-Mev;~ ransition would lead to a less negative value of A’s ln the c.m. system. One might expect from statistical considera- E tions that adding 185 events to an existing 236 could hardly change the conclusions. However? *work perforrnd under the auspices of the U. S. (a) it turns out that, partly because of a larger toinic Energy Commission and also eupported in part observed up-down decay asymmetry, and partly the Office of Naval Research. because of a smaller observed decay asymmetry +NOW at LOS AI-- Scientific Laboratory, ~0s in the production plane, we can set a substantially -08, New Mexico. smaller limit (about one-third as large) to the Phys. 5, 34 (1958). r ZHerrmannsfeldt, Mason, St%eh, and Allen, Phys. amount of parity-nonconserving amplitude in the ev. 107, 641 (19.57). , experiment reported here than in the 1.12-Bev/c 3Herrmannsfeldt, Staelh. and Allen, Bull. Am. e.xperiment; and (b) it is conceivable that a par- VS. Soc. Ser. 11, 2, 52 (1958). ity -nonconservi?g production amplitude could L&rrmannsfeldt, Burman. Staelin, Allen. ad increase substantially between 300 and 375 Mev/c. =aid, Phys. Rev. Lett. L, 61 (1958). Figure 1 shows the observed decay-asymmetry R. Penning and F. H. Schmidt, Rev. SJ. Phys. 105, components in the production plane plotted 7 (1957). against 8, the hyperon c.m. prductlon angle. In the left half of the figure we plot the front-back (FB) asymmetry in the n-c.m. coordinae system, FURTHER SEARCH FOR PARITY in which the positive direction is along P(r in- NONC0NSERVATK)N IN ASSOCIATED cident). The right half of the figure shows the PRODUCTION* left-rigfit (LR.)asymmetry in the Eme system. positive direction is along (a in$, where rank S. Crawford, Jr., Marceilo Creati, *The I Il-p+x- (2) y then, by virtue of its large decay-asymmetry ter, exhibit a decay asymmetry In the ion plane. earlier Letter we reported our analysis 6 events of the type (1)+ (2), produced by -, -3., -1 0 f g 1-8 -2 .L 0 L , Bevjc picns incident upon a liquid hydrogen 35 1s cos @ cas @ e chamber, leading to A’s of 300 MeT/c momentum.s nose results nere consistent FIG. 1. Decay asymmetry com@nenta In the pro- zero decay asymmetry in the production duction plane (see text). .- 11 :- 106 107 2 M E T E U S AU,I ./ . E-810 QlmUieu ligure 1 108 restriction on conventional cascade model calculations which predict the dkkribukions of all particles produced in heavy ion interactions. 2. Experimental method The experimental method was described in previous publication^^*^. Briefly, experiment E810 measured charged tracks in three TPC (Time Projection Chamber) modules in a magnetic field. The detector covered the forward hemisphere in the center-of-mass. The . trigger, as described in Ref. 5, selected centrally enriched events for data recording. For the final data sample we selected the most central events using a cut on the highest multiplicity of the negatively charged tracks within our good acceptance. We found this to be a reasonably good measure of the centrality from both the increased yield of K;’s and A’s as a function ‘of this multiplicity5 and from Monte Carlo studies of the correlation of impact parameter with this multiplicity. We selected the most central events from the Si target corresponding to a cross section of approximately 100 mb, and for Pb corresponding to a cross section of approximately 300 mb. These cuts correspond to approximately 10% of the geometric cross sett,ion. Since we have shown in Ref. 5 that the yield of A’s and K;’s is linearly dependent 011 our centrality selection criterion (negative multiplicity), any tighter cut for centrality selection is not justified because of limited statistics and our estimated systematic error of 20%. Thin targets were used to reduce 7 ray conversion which would give incorrect hadron multiplicities. We used a 0.122 cm thick Si target (L3% radiation length) and a 0.02 cm thick Pb target (3.5% radiation length). For more details on the experimental method see R.efs. 5 and 6. The effectivemasses for K;’s and A’s were calculated by kinematic hypothesis by assigning a proton or a pion mass to the charged tracks which form a vertex away from the point of interaction (see Ref. 6 for more details). ;e00 E 600 n >EO u 300 :300 -250 400 - 200 300 - 150 200 - 100 loo - 50 0 M(Tc-*-) - GeV/c’ M(pn-) - GeV/c‘ K’, Effective Moss A Effective Mass Fig. 1: (a)- Erective mass plot of the X+T- hypothesis for decay vertices from Pb target with vertices removed if they satisfy the A effective mass cuts. (b) EfTective mass plot of the proton A- hypothesis for decay vertices from Pb target. i 109 Lambda Multiplicity Si-PB Data 14.5xR GeV/c HlTH POISSGN FITTING I I I I I I UJ I I 1.0 20 3.0 4.0 5.0 6.0 7.0 # of Lambdas/Event 23-FEB-93 l2:P52 -.. .. Figure[5.25] Number of central events with multi-A production. 110 Si on Si - K,O mTinverse slopes Si on P~J- K," m, inverse dopes 0.m 0.25 0.20 -2 0 Y 0 a -0 0.1s eII L s.0 -= 0.10 0.05 0.00 1.AO 1.70 2.0 2.30 2.60 2.90 5.20 3.50 1-40 1.70 2.0 2.30 2.60 2.90 3.20 3.50 Rapidity Rapldlly Fig. 3: (a) Inverse exponential slopes for K:'s from the Si target. The points are fits to an exponential in each rapidity bin. The solid curve is the result of our global fit, not a fit to the points. The statistical error on the curve representation is'similar to that shown on the individual points. The dashed curve is the prediction of AGSHIJET+N'. (b) Inverse exponential slopes for K;'s from the Pb target. . A Rapidity - SiVSi A Rapidity - Si+Pb 5.0 t c 0 Reflected dolo 1.60 0 (28%~~)Blobel 1.40 z 1.20 DL .- 1.00 Px l- 0.80 0.60 0.10 0.20 0.0 -0.10 0.50 1.10 1.70 2.30 2.90 3.50 Rnpidity Fig. 4: (a) Rapidity distribution for A's from the Si target. The solid points above a rapidity of 1.7 are our measurements. Errors showi are tatistical only. The open squares represent the measurements of Ref. 8 scaled up by 28. The solid curve is the prediction of the ARC model. The dashed curve is the prediction of the AGSIIIJET+N' model. (b) Rapidity distribution for A's from the P6 target. Aw +Au. The result of this scaling is shown as a solid hu on Au - h Rapidily curve in Fig. 4. dashed curve is the prediction of ., , .I _, _.*.....I The 16.0 the ARC model and the dotted curve is the prediction 0 18.0 Rellccled Oalo 0 Qalo of the RQMU nod el. . .. 17.n '~RCprediclion 5. Discussion and coticlusioiis 5. 10.0 -.z.a v: 8.0 As can bc seen from Fig. 4, our nicasurernents of > thc A rapidity are in good agreement with the scal- 6.0 ing of the rapidity measurements of Ref. [2] by the measured kaon yield from [7]. In the rapidity 4.0 Re[. region of 2.0 < y < 3.2, where we have good ac- 2.n ceptance for A production, we are in good agreement with the predictions of thc ARC inodcl for the rapidity I, n I./ I-...,._,___.._.,._,__. I10 04 ('3 17 1.6 70 21 18 distribution. Tlic RQMD model sceiiis io underpredict Raptdill the yields in that rapidity rcgion. Our measureinents Fig. 4. Rapidity distiihutioii for A's. The solid curve i%the result of the in, distributions do not agree near mid-rapidity or scaling Si +Si data explaincd in tile text. Tlic daslted curve wilth the model predictions of either ARC or RQMD ARC prcdiction. 1Iic dotted curve is the KQMV prcdidim. is lite as can be seen in Figs. 2 and 3. Thc inverse slope ErrMs sliowii :IIC esplnicicd iii ~lictcxt. m, ineasureiiien~sscem to have a larger increase lowards ward heniispherc about the mid-rapidity point y = mid-rapidity (y = 1.6). This is verified by calculating 1.6. In ordcr to dctcrmine the rapidity distributions the x2 for our 41 measurements of 1 /N-d2N/dyd$ by integrating over lit, and to determine the contribu- in comparison with the two niodels and the Si + Si tion due to unmeasurcd regions of (he transverse ino- ineasurements of Ref- [ 2 J . For ARC we obtain a x2 mentum pr we have fitted our acceptance corrected of 416 for 41 points and a x2 of 208 if we allow the data to A-exp(-B-nil). Since the coefficients A and overall normalization of the data to change by 30%. B havc a strong correlation we havc calculated er- For RQMD we obtain a x2 of 175 and a 2 of 174 rors using a tcchnique previously described in Ref. for a change cf normalization of 5%. [2].This techniqueconsisted of fitting all of our data In summary, our measured A rapidity distribution points in y and nil with A-exp(-B-ni,) whcre A is for Au + Au central interactions agrees with the xal- an arbitrary constant independent of rapidity and B = inp ofSi + Si measurements of Ref. [ 21 and with the a+b-cosh(y-yo) +c- (y-y~)~/m,,witha, 6and predictions of the ARC model. The transverse mass c independcnt of rapidity and yo = 1.6. We needed distributions become less stcep at mid-rapidity corn- to add the c term to an earlier [2] parametrization in pared to the Si + Si ineasurernents or the predictions order to obtain a good fit to our data (x2of 38 for of ARC and RQMD models. A possible explanation 37 D.F.). Without this term we obtain a of 94 for or this effect is increased transverse flow [ t I] at mid- n x2 38 D.F. (CL< To determine the statistical er- rapidity in the heavier system. rors wc mapped a x2 contour of 1 a away from our best fit. It should be noted that these errors contain the contribution due to the uncertainty of extrapolating to Acknowledgement unmeasured regions of m,. We estimate an additional systematic error of -10%. Using the global fit to A We wish to thank the members oC the AGS deparl- and data from Si+Si interactions [2] we obtained ment and the MPS staff for their support during lhis thc ratio of A/C production. We then used the data experiment. We thankD. Kaliana for providing us with of Ref. [7] for K+ and K- production on Au -I-Au events from thc ARC model. We are grateful to H. and the approximation that K," = (K++ K-) /2 to Sorge for access to the RQMD code and advice on scale the A production of Ref. [2] from Si + Si to running it. 112 . .. or negatively charged tracks which form a vertex. For more details on A recoustructiori and its rapidity distribution, please refer to Ref. 7. With - 3000 well defined A's from the Pb target, we successfully found the E- signal with the following proceedures: We only used those A's and negative tracks( with sagittas _> 0.375 cm) that did not come from the primary vertex. When a A and a negative track formed a vertex, we took this as a possible E- decay--. vertex and extrapolated it to the primary vertex as a helix with a momentum vector of I?(=-) = @(A) + $(x-). A typical, reconstructed Z- decaying in our TPC module is shovn in Fig.1. ~ For all the vertices that survived the above cuts, we calculated their effective mass with the 7r-A hypothesis as plotted in Fig.2a. We selected those 97 candidates that lie in the range of 1.306-1.336 GeV/c2 as our E- signal. Those 19 wliich lie in the range of 1.280-1.294 GeV/c2 and 1.348-1.364 GeV/c2 are treated as backgrounds. 3. Results and Discussions Due to the limited statistics, we can only do a model dependent acceptance correction to our E- data. In order to ca.lcidate acceptances, a complete Monte Carlo simulation of events was perforined using GEANT. Events were generated using the AGSHIJET+N* model. The generated, TPC's bits included all the known effects of the detectors apertures,eficiencies, resolutions, and distortions. The same code has been wed to calculate the acceptance of A data and proved successful7. The lifetime of the E- is CT = 4.92 cm as given by Particle Data Group. We measured the acceptance corrected decay distribution as a function of proper time as shown in Fig.2b, which is in good agreement with the known value. This ghes us confidence in our acceptance calculations. The acceptance corrected rapidity spectrum using the AGSHIJET+N* model for the E- is shown in Fig.3a dong with AGSHIJET+N"'s prediction scaled up by a factor of 4. This production is equal to 0.15 E- per central event I- * ll I I- ll 1.28 1.3 1.32 ' 1.34 1.36 4 -- 8 12 16 M(~F-A) GeV/cZ z LIFE TIME cr (Cm) Fig2 a): Effective mass plot of x-A hypothesis for the decay vertices. t): The Z- decay distribution from central events. The dashed curve is not a fit, but the known value e-cT/4*g2. ! sonably well for Si+Pb, although it failed by almost a factor of 2 for Si+Si.6f7 AS pointed out in Ref.12, the enhancement of particles with single strangeness can not serve as o. clean signature of the QGP formation, since it carries too much background information of the liadronized state. However, the theory of strangeness enhancement as a signature of QGP * still may Le important; the question is how to observe it! In a hadron gas, producing multi- strange hyperons requires rescattering among strange hadrons or multiple rescat tering of resonant states- This makes their enhancement difficult for the conventional models to ac- count for. During the QGP (Quark Gluon Plasma) phase transition into a HG (Hadron Gas) phase, Ref- 13 demonstrates that a. large antistrangeness content will build up in the HG phase while a large strangeness excess will be left in the QGP phase. This excess during ldronization coiifd favor multi-strange hypcron production as well its strangelet formation. With strangelet searches still not successful, we consider hyperons of multiple strangeness a much better probe for QGP than single strangeness searches. To push the strangeness enhailcement study to a new stage of QGP search, we have searched for a Z- signal in otir da,ta.. 2. Experimental Method E810 =as designed to cover a large rapidity range and record as much information as possible on an event by event basis. The detailed experimental method of E810 has been described in previous yublicati~ns~*~- Briefly, we measured charged tracks in three TPC (Time Projection Chamber) modules in a magnetic fierd. The detector covered the forward hemisphere in the center-of-mass of the nucleon-nucleon system. The trigger, as decribed in Ref. 5, selected centrally.enriched events for data recording. For the final data sample we selected the most central events using a cut on the highest multiplicity of the negatively charged tracks within our good acceptance. We selected the most central events from the Pb target corresponding to a cross section of approximately 300 mb. These cuts correspoiid to approximately 10% of the geometric cross section. The effective masses for A's were calculated by kinematic hypothesis by assigning a proton or a pion mass to the positively . .. b Fig1 a): The X-2view of a E- decaying in TPC module b): Enlarged Y-Z view of the ' same decaying E- 115 Figure 21: Proposed set up for the EOS experiment at the AGS (perspective view). 116 Figure 25: Psonstructed Au + AU event projected onto the pad plane. 117 E896 3aseline Configuration Analyzer (18 kG) Sweeper (70 kG) . '.1~~iinr~~$i~;i"-':4"''',.q"'-:' p*c,lpm' !i!b's-~~~l"d~::~~~. DDC :-. Muffins ._ ...... -...... ,\: . JY u ECD Beam qefinition: 1-2 Cerenkov detectors (-30 ps) beam and veto counters CENT / 2 beam vectoring detectors (-200 i.lm> coIilimat o r I J 11.6.GeV/c/N Au+Au, b=O fm, Hijet daughter of a neutral primary... High efficiencies for H1A: anti-A, and Ks reconstruction... 118 1 1 U.L 0.5 01 A Acceptance, Z,, = 0.0 cm 16 10 16 0.5 0 A Acceptonce, Z,, = 50.0 cm Figure 11. Experiments at the AGS Brian Cole Columbia University 6 119 A Measurements in E910 Brian A.Cole, H. Hiejirna, X.Yang, D. Winter ia University . RHIKEN Theory'Workshop November 11 1997 Outline 1. E910 Goals 2. Description of Experiment 3. E910 Data & Analysis 4. A, K, Measurement 5. Results 6. Future E910 analysis 7. Measuring A's in Au+Au Collisions . B .A. Cole, Columbia University Slide 1 RHIKEN Workshop - November 11, 1997 E910 - Collaboration R Fernow, H. Kirk, S. Gushue, L. Remsberg, M[. Rosati Broohven National Laboratory B.A. Cole, I. Chemakin, H. Hiejima, M Moulson, D. Winter, X, Yang, W.A. Zajc, Y. Zhang Columbia University,Nevis Laboratories M, Justice, D. Keane Kent State University G. Rai Lawrence Berkeley National Laboratory V. Cianciolo, E. Hartouni, M. Kreisler, R Soltz, M.N. Nambodiri, J. Thomas Lawrence Livemre Nutisnal Laboratory A.D. Frawley, N. Made Florida State University M. Gilkes, R.L. McGrath, Y. Torun SUM", Stonybrook S. Mioduszewski, D. Morrison, K Read, S. Sorensen University of Tennessee J. H. Kang, Y. H. Shin Yonsei University B.A. Cole, Columbia University Slide 3 RHIKEN Workshop - November 11,1997 CI 10 10 c I E910 @ AGS-Experimental Setue IMPS Magnet .i-:* Details \ “Opportunistic” expt. usini mostly existing equipment. EOS TPC Nearly complete coverage \ 1 of final state (with PID). Installed in the A1 (MPS) secondary beam line. MPS DC Ran for 4 months during the spring 96 AGS run. Used Be, Cu, Au and U targets. :ov at 6, 12, 18 GeVk Ranincident proton momenta. Collected 45million min. bias and “central” triggers. B.A. Cole, Columbia University Slide 4 RHIKEN Workshop - November 11, 1997 E910 - Event Display Picture A Typical A Decay Event in EOS TPC ------ Target 20 cm upstream of TPC tracks well separated at entrance A decays in TPC easily identified 0 TPC resolution: 0.3 mm in x (?), 0.7'mm in y 3 A decays before TPC also easily identified B.A. Cole, Columbia University Slide 5 RHIKEN Workshop - November 11, 1997 . E910 I Particle Identification dWdx Identification w dE1d.x vs momentum Obtain up to 128 AE sampleshrack Use (&/AX) vs p for particle ID. Pair conversion electrons to reduce electron contamination. 10 10- IO -2 10 -I 1 10 -7 p ( GeVIc2 ) " ? - 10 I 3 NEGATIVE W4 Y X '.. Ela \ a 16 7c t 10 10-5 L Ill I I I I I ,,,I lo-' 1 10 10 -2 10 -I 1 10 p (GeV/c) p ( GeV/c2) B.A. Cole, Columbia University Slide 6 RHIKEN Workshop - November 11,1997 - *V*Reconstruction A + pn- with 63.9% BR ICs+ n+n-(68.6% BR) Particle identification: - 30dE/dx cuts on proton and n- tracks. - e+e-pairing to remove electrons 0 dA ’ 1.0 cm PA 0 4.87 deg Beam 4 B.A. Cole, Columbia University Slide 7 RHIKEN Workshop - November 11,1997 . . E910 Strange Particle Production ID IW First detailed study of strange 2W - particle spectra vs centrality in o = 133 MaVIo' p-A collisions IS, - (18 GeVk p+Au sollisions) IMO - Analysis by X.Yang - Columbia 500 10-31 +++ Y Y Nov. 3, 1997 Nevis Retreat - Exp. Relativistic Nuclear Physics. Slide 7 E9lOamenteros Plot Method of “identifying” Vo’s without PID. Plot of p_L vs a = (PL+- PIy (PL+ + PL-) a = clcos ecm+c2, pL = p* sin 8,,, 0 For A, a = (O.l71pA)COS 8,,+0.7 “New” analysis w/ dE/dx PID, “Old” analysis wlo dE1dx PTD more statistics and “loose” Mi, cut 0.25 0.25 i . l.’?’R,.’ 0.225 0.2 L 0.1 75 &0.175 0.15 0.15 0.1 25 0.125 0.1 0.1 0.075 0.075 0.05 0.05 0.025 0.025 0 a B .A. Cole, Columbia University Slide 8 RHIKEN Workshop - November 11,1997 Compare- "old" and "new" analyses Old analysis has large backgrounds at large lcos 0,,1 New analysis has much less background (particle ID !!) New analysis shows 8,, dependent acceptance * 400 - 900 Data wIo Accept. Corr. - Old 6 800 200 700 u 000 - 600 800 - 500 600 - 400 300 400 - 200 New - 200 -LLL w -1.25 -1 -0.75-0.5-0.25 0 0.25 0.5 0.75 1 B .A. Cole, Columbia University Slide 9 RHIKEN Workshop - November 11, 1997 As expected, acceptance shows cos 8,, dependence. After acceptance correction, see excess near cos 8,, = 1. - Residual K, contamination - Real problem for polarization measurements (?) 4000 2 t 2E E9 10 Preliminary 3 0.45 Geant Simulated Acceptance Data afer Accept. Corr. 3500 [ 6 0.4 6 0.35 0.3 2500 3000 0.25 I I 2ooo 0.2 li 0.15 0.1 0.05 500 loo0 1 B.A. Cole, Columbia University Slide 10 RHIKEN Workshop - November 11, 1997 . Compare "old" and "new" analvses Old analysis has large backgrounds at large lcos 8,,1 New analysis has much less background (particle ID !!) New analysis shows 8,, dependent acceptance eJ eJ - k 1400 ,900 Datu wIo Accept. Corr. - Old 800 1200 0" I 700 1000 - 600 - 800 500 - 600 400 300 400 - 200 New 100 B.A. Cole, Columbia University Slide 9 RHIKEN Workshop - November 11, 1997 ecal directions (2) As expected, acceptance shows cos e,, dependence. After acceptance correction, see excess near cos 0, = 1. - Residual K, contamination - Real problem for polarization measurements (?) 2 4000 i4 ~9 IOPreliminary 8 3500 Data after Accept. Corr. c, 1 I I 3000 I 2500 0.25 1 2000 0.2 5 1500 0.15 I 1000 0.1 1 500 0.05 1 0 B.A. Cole, Columbia University Slide 10 RHIKEN Workshop - November 11, 1997 I- w 0 + , Compare "old" and "new" analyses Old analysis has large backgrounds at large lcos 8,,1 New analysis has much less background (particle ID !!) New analysis shows 8,, dependent acceptance 2 ,900 s Data wlo Accept. Cow. Old 6 800 700 ::::I1000 600 - 800 500 - 400 600 300 400 - 200 New 100 2oo -1.25t . I -0.75-0.5-0.25 0 0.25 0.5 0.75 1 1.25 B .A. Cole, Columbia University Slide 9 RHIKEN Workshop - November 11, 1997 As expected, acceptance shows cos e,, dependence. After acceptance correction, see excess near cos e,, = 1. - Residual K, contamination - Real problem for polarization measurements (?) 3 x E9 10 Preliminary 3 3500 Data afer Accept. Corr. CJ 4000 2500 0.25 5 30002000 0.2 1 I 0.15 fi 0.1 1 500 0.05 + 1°00 1 B.A. Cole, Columbia University Slide 10 RHIKEN Workshop - November 11, 1997 t- w 0 r 8 * E910 soreconstruction D Reconstruct e+e-pairs from y conversions. Find no +w dtdy vs rapidity for no Analysis by H. Hiejima, Columbia L 8- ID 1102 ,pJ 4s - 600 3 Enrries 50684 L - Mean 0.2628 40 RMS 0.3024 2 4- v 35 - ++ 300 5 30 - 200 L 2s - 20 - -0- Ill 15 - 0 0.2 0.4 0.6 0.8 1 10 - -Q- mass ( orig )pidcut 350 5 - 1000 300 -0- 0 I1IIIIIIIIIIIIIIIIIII IIIIIIIIII I IIIIIIIIIIII 800 0 0.5 I 1.5 2 2.5 3 3.5 4 250 Rapidity 600 200 150 Opens many possibilities: 400 100 @ 0 -+ n+n- no 200 + Ay 50 CO 0 0 K* + K*n0 0 0.5 1 1.5 0 0.5 1 1.5 2 .q+yy?? mass ( orig Jpidcut mas ( mixed ) pidcut Nov. 3, 1997 Nevis Retreat - Exp. Relativistic Nuclear Physics. Slide 11 * * .= -L E910 --Lambda Inv. Masses Compare “old” and “new” analyses Observations 23 0 New analysis has --- HIPAGS’! better SIN even wlo 600 cut on ._...... _-DNP ’97 8,. 0 New analysis has less 500 1 background at low Minv 0 Xihong: - Low MhVbg mostly from fake Vo’s. - High Mi,, bg mostly from K,. Difficult to “see” K, background in the inclusive distribution. pn-Invariant Mass (GeVlc)-.., B.A. Cole, Columbia University Slide 12 RHIKBN Workshop - November 11, 1997 6- w w E910 Lambda Mass vs Rapidity A Invariant Mass at DilfSerent Rapid@ Region Observations See “fake” Vo background at low rapidity (expected). I See larger K, contribution 1 high rapidity. See effect of worsening TPC momentum resolution Where are the A’s at y>2.6 -Most likely due to stopping - “Efficiency” loss - Unknown problems ?? 9 A polarization at large y problematic wlo additional particle ID due to K, Note: currently not using relativistic rise in dEldx. B ,A. Cole, Columbia University Slide 13 RHIKEN Workshop - November 11,1997 E910 - Lambda Inv. Masses Compare “old” and ‘‘new99analyses Observations New analysis has _-- HIPAGS’ 96 better S/N even w/o n ll...... -- DNP’97 cut on eCme New analysis has less 500 background at low 1 ! Mi, I 0 Xihong: i M,, bg mostly 300 i - Low from fake VO’s. 200 - High M,, bg mostly from K,. 100 Difficult to “see” K, p background in the inclusive distribution. pn-Invariant Mass (GeVlc) B .A. Cole, Columbia University Slide 12 RHIKEN Workshop - November 11,1997 P w w E910 &Lambda Mass vs RapidiQ A Invariant Mass at Different Rapidity Kegion Observations 80 0 60 See “fake” Vo background 40 200 500 at low rapidity (expected);. 20 100 0 See larger K, contribution ; 0 -n 0 1.1 1.15 1.1 1.15 :m1.1 1.15 high rapidity. 0.0 < y < 0.4 0.4 < y < 0.6 0.6 < v < 1.0 400 0 See effect of worsening 300 TPC momentum resolution 200 2000 500 Where are the A’s at y>2.6 100 ::z5000 ~ 1.1 1.15 2500 ~ 1.1 1.15 -Most likely due to stopping 0 1.1 1.15 - “Efficiency” loss 1.0 e y < 1.4 1.4 < y < 1.8 . 1.8 < y < 2.2 c I - Unknown problems ?? 20 9 A polarization at large y 15 problematic w/o additional IO 20 particle ID due to K, 5 -n 0 Note: currently not using 1.1 1.15 1.1 1.15 2.2 < y < 2.4 2.4 < y < 2.6 2.6 < y 3.6 relativistic rise in dE/dx. B .A. Cole, Columbia University Slide 13 RHIKEN Workshop - November 11,1997 4 c c .4 “Centrality” is difficult to measure in proton-nucleus collisions. Previous p-A experiments: characterize centrality with # slow protons “Rule of thumb”, number of primary collisions, Y = ,/= First detailed study of centrality dex>endenceof A Production in D-A collision, Slow proton has p e 1.2 GeWc ‘Y 10-i h+++ 1o-2 + I L Number of slow protons 2- Y ~ B .A. Cole, Columbia University Slide 14 RHIKEN Workshop - November 11, 1997 F w Ln E910 - Future of Lambda Analysis Detector Analysis TPC - Improvements in “hit-finding” for close tracks. Particle Identification - Currently tuning up TOF and Cherenkov identifi ation - Relativistic rise dE/dx helpful for tracks that miss Cherenkov. Downstream tracking - Improved (x10) momentum resolution at high p. - Eventually will reconstruct A decays at end of or after TPC. Physics Analysis 0 Improved A reconstruction cuts Other targets (Be, Cu), beam momenta (12 GeV/c) Lambda polarization measurement A A correlation analysis B.A. Cole, Columbia University Slide 15 RHIKEN Workshop - November 1 1, 1997 Lambda Polarization Correlations (2) How to design expt. from scratch (starting point) ? Use large-acceptance detector (rate, . .) 0 Measure at moderate to high rapidity - Angular acceptance is better for given geometric size. - Get downstream from target & away from the junk. - Less multiple scattering, energy loss, .. . - Need good tracking resolution, particle ID. 0 Make azimuthal acceptance uniform - “Guaranteed” to have bias in 8,, - Look only for correlations azimuthally ?? Start with/use asymmetric collisions - Demonstrate no effect in control measurement (e.g. O+Au) - Less uninteresting corona in (e.g.)Ag-tAu than Au+Au ? - For central interactions, A at mid-rapidity and above must come from high baryon density region. B .A. Cole, Columbia University Slide 17 RHIKEN Workshop - November 11,1997 RIKEN BNL RESEARCHCENTER SYMPOSIUM ON COLOR SUPERCONDUCTIVITY, INSTANTONS, AND PARITY (NON?)CONSERVATIONAT HIGH BARYON DENSITY f NOVEMBER11,1997 * PHYSICSDEPARTMENT SEMINAR ROOM AGENDA 09:OO -- 09~30 Krishna Rajagopal (MIT) QCD at Finite Baryon Density: Nucleon Droplets and Color Superconductivity 09:30 -- 1O:OO Mark Alford (IAS) 1o:oo -- 12:oo Thomas Schiifer (INT) Instanton Dynamics L.. 11:oo -- 12:oo Yang Pang (Columbia) ParityViolation Observables in AA 01:OO -- 01:30 Nicholas Samios (BNL) Lambda Polarization Measurements 01:30 -- 02~15 Brian Cole (Columbia) Experiments at the AGS 02:30 -- 05:OO Discussions 139 RIKEN BNL Center Workshops Title: Physics with Parallel Processors Organizers: R. Mawhinney/S. Ohta Dates: April/May 98 (tentative) Title: RHIC Spin Physics Organizers: G. Bunce/M. Tannenbaum Dates: April 27-29,1998 Title: Quarkonium Production in Relativistic Nuclear Collisions Organizer: D. Kharzeev Dates: Sept. 28-Oct. 2,1998 Title: Dynamics of Chiral Fields in Nuclear Collisions Organizer: D. Rischke Date: Week of April 27th Title: QCD Spectroscopy Organizers: M. Pennington/W. Marciano Dates: TBA Title: Polarized Parton Distributions and Event Generators Organizers: TBA Date: Summer (tentative) Title: QCD Vacuum and Phase Transitions Organizer: E. Shuryak Date: Early spring Title: Semiclassical Fields in QED and QCD Organizers: A. Baltz/D. Rischke/L. McLerran Date: Early fall Title: Quantum Fields in and out of Equilibrium Organizers: R. Pisarski/H. de Vega Date: Week of October 26th Title: Many-Fermion Systems ... (Bielefeld follow-up) Organizers: M. Creutz/M. Gyulassy Date: Noverrber 1998 Title: Many-Fermion Systems at Finite Densities Organizers: T. Blum/M. Creutz Date: early '99 Title: Spin Physics Mini-Workshops Organizers: N. Samios/R. Jaffe Date: Quarterly For information please contact: Ms. Pamela Esposito RIKEN BNL Research Center Building 510A, Brookhaven National Laboratory Upton, NY 11973, TJSA Phone: (516)3443@97 Fax: (516)344-4067 E-Mail: rikenbnlQbnl.gov Homepage: http://penguin.phy.bnl.gov/www/riken.html RIKEN BNL RESEARCH CENTER COLORSUPERCONDUCTIVITY, INSTANTONS AND PARITY (NON?)-CONSERVATION AT HIGHBARYON DENSITY NOVEMBER11 1997 Nuclei as heavy as bulls Through collision Generate new states of matter. 7: D, Lee Speakers: M. Alford B. Cole M. Gyulassy K. Raja opal Y. Pang I? Samios T. Schaer9 N. Organizer: M. Gyulassy