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Title THE A1 AND K(1320) PHENOMENA -- KINEMATIC ENHANCEMENTS OR MESONS?

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Authors Goldhaber, Gerson Goldhaber, Sulamith.

Publication Date 1966-03-01

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(JCRL- 16744 • L

Proc. 4th Anniv. Symposium Inst. Math, Sci, Madras, India January 3 to 11, 1966,,

UNIVERSITY OF CALIFORNIA Lawrence Radiation Laboratory Berkeley, California

AEC Contract No W-7405-eng-48

** THE A 1 AND K • (1320) PHE]OMENA- KINEMATIC ENHANCEMENTS OR MESONS?

'Gerson Goldhaber and Sulamith Goidhaber

March 1966 -111- UCRL- 16744

This articleis based on the lecture notes prepared by the authors for the 4th Anniversary Symposium on Resonant States of Elementary Particles, held at the Institute of Mathematical Sciences, Madras, India, on January 3 to 11, 1966. Due to unforeseen circumstancesthese lectures were never presented. The article is to be published in the Proceedings of the 4th Anniversary Symposium. -1- UCRL- 16744

The A 1 and K'(1320) Phenomena-- Kinematic Enhancements or Mesons?

Gerson Goldhaber and Sulamith Goldhaber

Lawrence Radiation Laboratory and Department of Physics University of California, Berkeley, California

March 1966

INTRO DIJCTION In this article we discuss the similarity, down to some very fine details, between the well-known A 1 phenomenon and the more recently discovered K(132O) phenomenon. We wish to point out that this similarity is truly remarkable and can hardly be coincidental. We will try to present the pros and cons, to the extent they are known to us, for the assignments of "kinematic enhancement" or "meson" to the A 1 and K**(1320) respectively. In view of the similarity between them we feel that when the ultimate decisions as to their identity can be made they may well turn out to be the same type of physical phenomena, namely either both kinematic enhancements or both mesons.

Deceased. Sulamith Goldhaber died suddenly on December 11, 1965. At the time she was holding a Guggenheim Fellowship and the appoint- ment of Visiting Professor at the Institute of Mathematical Sciences in Madras, India. -2- UCRL-16744

I, THE EXPERIMENTAL EVIDENCE FOR THE A f PHENOMENON

Before we comment on the subtle features involved in theA 1 let us review the current evidence for this phenomenon. The A 1 has been observed in four di:tinct. experimental situations. These are:

High momentum, 12 to 18 BeV/c, TT interactions with complexnuclei in a heavyliquid bubble chamber, The reactions ± Trp - p 0 Trp in the momentum intervals 2,75 to 4BeV/c observed:inhydrogen bubble chambers, The reaction

+ 0+ at 8 BeV/c and irp - p ° Trp at 6 BeV/c in hydrogen bubble chambers. High momentum, 17 BeV/c, 11 interactions in.photographic emulsions.

We will now consider these.groups of exper.iments inturn: (a)0 In a series of experiments, studying the .*7VT+: productioi, without visible nucleon excitation, using the Ecole Po.lytechnique,heayy'•liquid bubble chamber at CERN, Ailard et al, have observed avery marked peak in the 1Tr+ mass at 1,08 BeV, Furthermore, theyfindthat.if they limit their sample to events with low four-momentum transfer to the nucleus, nearly the entire A l peak is associated with p° formation(see Fig. 1) This is in accord with the decay mode A- Tr p ° discovered in the exper- 2-4 iments with hydrogen. No appreciable A 2 formation is observedin the data on complex nuclei, (b), In Fig. 2 we show arecent compilation of the data inthe 3- to 4-BeV/c region, For these data events with p o formation have been. se - lected and the N' band has been removed. Here both the A 1 and A 2 peaks are observed, although A 2 formation..is much more prominent than A 1 formation, Figure 3 shows the data of Alitti et al (SOBB Collaboration) at 2,75 BeV/c, which is not .includedinthe above compilation. Alitti et al. T1,0 also have reasonably good evidence for, the p decay mode as well as the p ° 1r decay modeof both the A 1 and A 2 , If one were tocharacterizethe -3- UCRL-16744

16 GeV/c ir on Nuclei ECOLE POLYTECHNIQUE, CERN, MILANO, SACLAY, U.C.BERKELEY

T11Tfl Effective Mass

70 AU events (989) R Lowcj events 60 Lowa events with -

50 (11 C > it LJ1 uJ 40 0 iUL, U -o E Z20

+ 4..

4 05 10 15 21) 255 3.0 M&eV

MUB-9849

Fig. 1• The three-pion mass distribution from the heavy-liquid chamber experiment. -4- tJCRL-16744

+p—p°+ +p GOLDHABER ET AL. 140 3.7 8eV/c Combined data CHUNG ET AL. 120 * 3 to 4 BeV 00' 2500 events 80

oa 60

a,- 20 CL

(fl 0 - GOLDHABER ETAL. ++p .65BeV/c w 100 ADERHOLZ El AL. a,> 4.OBeV/c 80 LANDER ET AL. 80 L

60 E 40 3.5BeV/c

0 • i • 900 1300 1100 0.5' 1.3 47 M(irp°) (MeV) M(7T,,°°) (8eV)

MUB-9848A

Fig. 2. Compilation of the 7T p ° mass distribution from the available data in the 3- to 4-BeV/c region. The N+ events have been removed in these plots.

V -5- tJCRL-16744

-rifc 2.75-V/c ço

47.< 401,a

N* exc/u _534ev-5

65Ot1ev

011

M(irirn- ) (It4eV)

ir -ppM°

4Z40,LIZ 581ev)

E t1('p7ri A, ' 48Of1ev

ONE

M(TThi°) (MV)

.MUB-9796

Fig. 3. (upper) The mass distribution from the trp interaction at 2.75 BeV/c. The shaded area corresponds to p?'Tr events. (lower) The ir+ missing-mass distribution. The shaded area corresponds to Tril events. -6- UCRL-16744

A± phenomenon in the 2. 75- to 4-BeV/c momentum interval in words, it couldbe described as abroad ttpedestaP ranging roughly from 10to1.4 BeV in the ii p ° mass. At the upper end of this pedestal sits a very prominent A 2 peak at = 1320 MeV (although the 6-BeV/c data 6 suggest M(A 2 ) =1290 MeV and the 8-BeV/c data 7: M(A 2 ) = 1280 MeV), At the lower end of the pedestal a less prominent A 1 peak at 1080 MeV may be noted, 7 The rr p 8-BeV/c data, taken at face value, appear. to give two very clear-cut peaks, A 1 and A2 , of nearly comparable intensities andwith a very definite separation between.them (see Fig. 4). On the other hand the 6 very recent data of Barnes et al., iT p at 6 BeV/c, with about half as many events, do not show any evidence for a distinct A l peak (see Fig. 4), Although the statistical accuracy of the two experimentsis such that we are not really dealing with a serious discrepancy, it does make one wonder, however, whether the truth might not lie somewhere in between. 8 The data of Boz6ki et al, from photographic emulsions are given in Fig. 5. These data show a distinct three-pion peak. The data confirm the production of a peak from interactions on complex nuclei, and are compared with a diffraction dissociation model. No information is available from this experiment on the finer details we shall discuss subse-

quently 0

U. THE EXPERIMENTAL EVIDENCE FOR THE K(1320)PHENOMENON

Indications for a K"(1320) enhancement were first observed:by 10 Almeida et al. in the Kp reactior at 5BeV/c. The effect is strongly reminiscent of the A enhancment. It was observed inthe reaction + K.p -"K I IT 'iT p. One observes no striking enhancement if one looks at the entire K+ tr . -ir + mass distribution. However, if one selects the events with the inthe K"° (890) band one observes a clear-cut band on a Dalitz plot for the three-particle" system K01r+p, Furthermore, the projectionof this Dalitz plot on the,K,IT+ mass axis shows apeak centeredat 1320 MeV, when the N (1238) bandis removed, Here the K ° is the S(J(3) analog of the p ° ,.which occursinthe case of theA 1 enhancement. Figure 6 shows the data of Almeida et al., who obtained 41 events after the abovetwo selec- •tion criteria were applied.

UCRL-16 744

8GeV/c rp INTERACTIONS Barnes et al. 6.-BeV/c ii -p AACF4EN -BERLIN -CERN COLLABORATION

> A,(1290) 50 452 (p.)EVENTS ---:311 (p')EVENTS WITH Ne 0 IC) A1(I080( [L 0 ((240 MeV) EVENTS REMOVED o 40 3 :I95Cp.)EVENTS WITH N 0 j1 ((240 May) AND 8) Na° (1240 May) 0. fl L. EVENTS REMOVED 30 "I z > C 8) > Li. s 0 20 It

0 = It ; 10 .0 E 0.18 0.99 Lia 1.38 1.58 1.78 L98 2(8 2.38 2.58 Z 0 M(p.i BaV/c' 1.0 20 3.0 (111'1i1) EFF. MASS, GeV.

MU B-9790A

Fig. 4. (left) The lrp mass distribution at 8 BeV/c incident Ir momentum. This represents the strongest evidence for a sharp A 1 peak. (right) The same distribution from the Tr - p interaction at 6 BeV/c. In these data no evidence for the A 1 was observed. -8- UCRL-16744

Bozki et al. 17.2-BeV/c r on emulsions

0 0 0.5 1,0 1.5 2.0

M(A 1 ) (GeV)

tJB-10190'

Fig. 5. The distribution of the effective three-pion mass for 142 events. The smooth curve is the effective-mass distribution predicted by the diffraction dis s ociation mechanism. -9- UCRL-16744

K°(1320)

Almeida Ct al. 20 - K±p-K i1rr p 5 GeV/c I8 K'(I175) 16 f out 14- \1

9•0H 1.0 l•I 1.2 1.3 (4 1.5 16 (.7 1•8 1•9 2•0 2•1 2•2 23 rrrr (&v)

32O

p_+1tP fr 99 EVENTS (b)

4-0

3-01

2-0- N3 4 .:. .

30 4O 90 6-0

MU B-9792 A

Fig. 6. The initial evidence for the K'(I320). The Kr1r+ mass distribution without K* selectiön The Dalitz plots for the K iip events. -10.- LTCRL-16744

In our own work with K ++ p at 4.6 BeV/c,' obtained from a run with the 80-inch Brookhaven National Laboratory hydrogen bubble chamber + exposed in a separated K beam at the AGS, we have observed a very sim- •.ilar effect based on 10 times the number.of events,, viz..,. 421 events after the same selection criteria are applied. (These datawere first presented at the 1965 Oxford Conference). We have studied.the two reactions

(1) it ii p (997 events), 0 0+ (2) -~ KIT1T p (454 events).

In (1) K 0 (890) is produced, while.in'(Z) both K 40 (890), and

K+(890) areproduced. . Figure 7':giethtia gi]øt Ior Reaction(i). Figure 8a and b shows the corresponding Dalitz plots for Reactions (1.) and (2). Here for .Reaction'(Z) both versions of K(890) are.chosen. The projec.tions.in Fig. 8 show the [K(890)it]+ mass squared.and massdistribu-

- tions for Reactions (1) and . (.2) separately as well as the combined-mass dis 'tribution. We observe a. very. distinct and sharp peak at 1320 MeV with 80 MeV in both Reactions (1) and. (2). Jongejans also presented data at the'Oxford.Conference from Kp at 3, 3.5, and 5 BeV/c (De'Baere et al. ), Thenumbers of events for Reaction. (1) after applying the abovetwo selection criteria were 102, 130, and 214 respectively, for-the three.momen. DeBaere et al. concluded from their data.that the I'(1320) must be a:kinematic effect, because they found that the location of the cener of the peak moves.as the ,K+ incident momentum changes. From Fig. 9, the central masses of the observect peaks(as. read off by us) for the three incident momenta are 1225, 1350, and = 1225 MeV respectively. 13 Thev.ariation they observe does not appear to show a consistent trend and could thus. be in part statistical. VA Although these data certainly favor, the kinematical interpretation, we feel that it is not fully conclusive just on.this evidence alone. Forexample, it is conceivable that the 'K(1320) gets produced only above 3.5 BeV/c incident momentum. We thus feel that more data will be needed to settle this point.

p tJCRL-16 744

2.6 I I I I 2.6 K++p_K++ir++ .ir+ \ (a) p 4.6BeV/c N 997 events 2.2 •'\ 433 events, 2.2 0.84 ~ M(Kirj ~ 0.94BeV CO 1.8 1.8 j:- -9.

14 14 .'..

U..

I I I i.c I• I 1.0 210 160 120 80 40 0 -

468 events - 190 - JL1 1.I2:5M(pn-):!!~ 1.32

CO BeV

cr80 - q 0 - a) 0

u,60 -

2O S

M (K+ ir ) (BeV)

MU 6 9276

Fig. 7. In the triangleplot for the reaction K+ + pK++Tr++1T_+p at 4.6 BeV/c, the K(1320) phenomenon corresp,pnds to the K (89O) events found in the vertical band outside the N+ horizontal band.. tJCRL-16744

Kp 4.6 BeV/c

K++p+ K++ ,r+7r+ +p I 259 events, K*O j Combined C++ K++p_KO+ir+ a.O+p N out (0) 0.84' M(Kari' 0.94 BeV (b) 0.84' 10(K 0 ,r0)' 0.94 BeV, or 0.84' M(K 0 ,r'i'O.94BeV

6.0-

04 421 events, all K*N* out - . - o .::. .. N. > /. ... U 4.0 \ ~ - 3.0 - 0 cj I d

2.0 - U a. K++p ._* KO+ ,r+ ,rO +p r 1.0 1 I I I 162 events, I 30 2G C a, either K in, 401- "i.. '(c) N bond removed (d) N bond removed > (g) U N* out I - 259 events - 162 events - 20 10- - 10

0.5 2.5 4.5 0.5 2.5 4.5 0.8 1.6 2.4 0.8 1.6 2.4 M2(0 0 ,r+) (8eV)2 M2 (K,r)' (8eV)2 M (K*,r )+ (8eV) M (K) (8eV)

MUB-9794A

Fig. 8. The Dalitz plots for the Kirp events. The projections are 4, shown in (c) and (d) in mass squared and in (e) and (f) in mass. The combined distribition is shown in (g). The latter shows the mass peak in the Kir mass distribution at 1320 MeV/c and a possible indication of an enhancement at 1400 MeV/c. -3- tJCRL-16744

- -.

DeBaere et al. .

Bishop et al. 3.6-GeV/c K+p

K+it_K* p u>1.4GeV/c 2 iv r 3GeV/c 102 events 10 1

H 3.5 GeV/c 25 20 I I 130 events > a) T 20 0 10 /

LU eV/c 712 eventss -zIO 20r1

5 10-

0 0.8 1.0 1.2 1.4 1.6 1.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 (K07T+7T0 ) - P.1 AS S (B eV/c2 ) + + - 2 MASS K Tcit GeV/c

MU B- 9881 A-

Fig. 9. (left) The same mass distribution as in Fig. 8 from the experiment of De Baere et al. Fig. 10. (right) The same distribution as in Fig. 8 from jhe data of Bishop et al. ; the shaded region corresponds to K'(890) selection. In these data the N+ has not been removed. The authors point out the small enhancement at 1400 MeV/c. -14-.

.11 One amusing feature is that not only does the 1320-MeV K iT peak correspond to the A 1 , but there is also the possibility of a second peak due to the K'(1400) decay via K(890) + Tr, which would correspond to the A 2 . Thus here again we would have a situation in which we observe an SU(3) analog (this time from the 2+ nonet), The very persuasive arguments of Glashow and Socolow 14 on the 2+ nonet predict [ K (1400) - K(890) 1T]/[K(1400) - Ku] = 0.6. Although we observe a small peak in the K (890) u mass distribution in the region of 1400 MeV (see Fig. 8), our present data do not allow us to give a significant deter- 15 mination of this ratio. Bishop et al. have shown some evidence for this decay mode in their experiment with 3.6-BeV/c K+p (see Fig. 10), while 16 Chung et al, quote a. limit for this decay mode. Furthermore, Derrick also presented evidence for this decay mode, based on the Kp interactions at 5.5 BeV/c, at the 1966 New York Meeting. 17

III. KINEMATIC ENHANCEMENT MECHANISMS Even before its discovery, the A 1 was predicted as a kinematic enhancement. Thus Pais and Nauenberg t8 predicted a peak in the up mass at the position of the A 1 on the basis of the Peierls mechanism. 19 However, more careful study of this phenomenon, in particular by Goebel,2° indicates that the Peierls mechanism cannot give rise to such apeak, at a physical mass value. New mechanisms have been suggested more recently, again considering the A 1 as a kinematic enhancement. A. The Deck Mechanism 21 In Deck s model, and the further elaboration by Maor and O!Halloran, 22 it was shown that the qualitative features of a peak in the up mass near the A 1 can be obtained from an OPE calculation in which the lone pion scatters off the nucleon. (These models differ in detail in that Deck, in the spirit of the Drell process, has considered the up scattering vertex purely as diffraction scattering. Maor and O'Halloran, on the other hand, have considered the physical up cros sections ith..,.ff-th:e:-mas s-shell corrections. At the higher up mass values these two approaches differ only

slightly. ) Figure 11, 'gives thereltof:the càlculatibns. hrMao -t5. UCRL-i6744

• •c'J 0.20 • a) (9 C' I.

L-

0.05

b 1.0 2.0 3.0 1.0 2.0 3.0

u 2 [(GeV )2]

MUB-10568

+ Fig. (a) r -p 0calpulated mass distribution for 3.6 GeV/c incident momentum. (b) rr m -K 40 calculated mass distribution at 3.0 GeV/c. Calculations based on asymmetry. of 7r+p sc3ttering above N+ resonance. Both distributions are compared with the, appropriate normalized phase-space distributions (dashed lines) -16.- UCRL- 16744

and clHalloran. A wordof caution. We feell surethat the above authors:wi.11 agree with us that the exact shape, location of peak, and width of peak must be considered only as qualitative .indicatiohs from their calculations. In: particular, such questions as. absorption effects.versusrform .factors.and.the exact handling of spin >3/2 resonances.have not been settled.asyet. Furthermore,. Bose.sym metrization. effects . have not been included in the calculations. either.

If we take this model, involving ~ virtual pion exchange, seriously, it carries.with it some further speci.fic conditions, which can: be tested. We.can.state these as..follows: The p° should:be produced aligned with respect to.the incident direction, 0 such that the irr scatteringi angle a: in the p center of mass follows the dis - tribution:cos 2 a The Treirnan- Yang.angle'at .the 'p° vertex, should' be isotropic (except perhaps for small deviations due to absorption effects), The Treiman-Yang' angle at the Trp vertex also shOuld be isotropic (with a similar 'proviso for: possible absorption. effects), The four-momentum transfer distribution to the p° meson should. be "characteristic of the OPE model." The differential cross, section d 2o/d2dM of the lr±pvertex should, be similar 'to that .for free lr±pelastic scattering, (da 1/d) when averaged, over the corres.ponding mass interval. In'the- above discussionwe have made all statements .in.terms.of A 1 production. They are equally applicable to K (1320) production, .inwhich the p° is replaced.by the K(89O.), With respect'to. points.(a) through (d) we,.have two, control regions.we can consider. forthe A 1 (which is, here assumed'to, be a kinematical enhancement). First we can.. compare the angular.and four-momentum distributions.obtained..for the A band;.wi'th distributions:corres.ponding.to p ° Nff(1238) production. Here'we,havea control region, and, expect to see similarities in.the dis - N+, tributions, since the' is just part of the Tr ,. p scattering cross section, albeit a. veryj intense and well-defined, part. Secondly, we can, contrast the distributions:in:the A 1 . band.with those in. the A 2, band. Herewe expect to see radical differences, as the events in.the A 2 band. (aside'from background) definitely correspond.to a bona.fide resonancewith JP = 2+ . Furthermore even. if A 1 is a meson (of spin-parity Ziwe do not expect the same angular'distributions. However, onemight have expected UCRL- 16 744

c:omparable z(p) distributions (both corresponding to p exchange); but these fbserved to be areistinctly different. One further point of interest is the lack of asymmetry in p° decay: (the•..cosa distribution) .inthe A 2 band, while the usual asymmetry is present for the A 1 band (see Sections IV E and H). For the K"(i320) we have only the K'(890) + N+ events. ascontrol region, where we must again look for similarities, [As pointed out above, the K(1400)-* K (890) + Tr decay mode is not pronounced enough in our datato be useful as a region of comparison in analogy to the A21 , B. Other Mechanisms Other kinematic mechanisms have been pro.posed to explain the A 1 enhancement as well. Month 23 proposed triangle singularities as a source for 24 25 the enhancement, and Chang, and Dash et al consideredenhancements arising from Bose symmetrization effects. These mechanisms donot possess such well-defined tests as points (a) through (e) above, that can beperformed with the data; we will not pursue these .fu.rther here, (Months proposal would require considerablelow-mass iiir enhancement forthe A l , and.inrand/or Kir enhancement or both for K(1320), Noeffects strong enough to produce the observed phenomenon are seen. in either case, See Fig, .32 for the A 1 case,)

IV, THE EXPERIMENTAL RESULTS AND TESTS ON THE A 1 PERTAINING TO KINEMATIC ENHANCEMENT A. Results from the British-German collaboration 26 In this work (Tr + p.at 4 BeV/c) Aderholzet al, compared the experimental data with an OPE calculation similarto .the Deck model, .TheyYstiidied the iTp mass distribution (see Fig, 12a), the a scattering angle in the p ° 2 center-of-mass system, . see Fig, 12b and c, and the A distribution to the up system, Fig. 12d and c. In the latterr two the A 2 bandis. used as.a control region for the A 1 , and marked differences are noted, . .They conclude that the general .features of the events in the A 1 . region are described by the OPE model except for the height and narrow width of the A 1 enhancement, They thus felt that they could not decide between '.meson" and "kinematic enhancement. 11 -18- UCRL-16744

6O- dS U' 1-2 (mb/GeV) 520 events 4,0-BeV/c irp ci 1_ri (a) A B B B H L M

20- jo

.4 .8 1.2 1.6 20 M Tr + (G eV)

mb/GeV2) 40 ri In Ii 30-f (d) C 0 C 30 70 events .0 E 0 o 20

•0 0 i : a)I-. 10 .0 E 0 .5 1.0 cO 2 (p/p) (GeV 2 ) 0 1 40 U' C . i ( m b/G eV 2 ) 0 (a 30 30- (e) C U., .0 E events O 20 U

0 o 10 10- df tn .0 E C L 0 Cos 2 (p/p) (GeV 2 )

MU B-9787A

Fig. iZ. The data from the 4-BeV/c ir +p experiment; (b) and (c) show the distribution of the irri scattering angle in the p ° center of mass. This was called a in the text.

EJCRL-16744

The work on the rrd interaction 27 The Trd reaction studied by Seidlitz et al. at 3.2 BeV/c and by 28 Abolins et al, at 3,7 BeV/c, allows one to rule out the isotopic spin T = 2 for both the A 1 and A2 . The argument rests on the comparison of the production rates for the A 1 and A2 in the reactions

- 0 - +- (1.a) iT d - p + TT +n + (p); p - rr iT

0 + - 0 _ or: +p +(); p (Ib) and +d p + +p + (p); p (2) irT thus they. search for therates of A- I p ° + from Reactions (Ia) and'(1b) and A - - p + ii from Reaction (2), which should be 1 1. 0 for T(A) = I and 1:I:8 for T(A) = 2, The data and14) that both A1 and A 2 correspond to T = I effects, Seidlitz .et al, stress in particular that the events in the A 1 region are associated with very, small to the A1 [i 2 (Trp° ) 15 (BeV/c) 2], which appears inconsistent with the interpretation of the A 1 as a resonance in 'rip scattering (and thus corresponding to p exchange) They cite the work of Cohn et al , 29 who observed w, production in the reaction Tr+ d- o + p (p) at 3.65 BeV/c (assumed to.proceed via p exchange). Cohn et al, find that no appreciable amount of w production occurs for A () 0,6(BeV/c) 2 , which is alsothe case for A 2 .production, The comments by Xuong In his talk at the ZndAthens Conference Ng, H. Xuong, reporting 28, on the data of Abolins et al,, made two further comments about the A 1 phenomenon. (a) He showed that in the reaction + one can u s e. the events corresponding to a p 0N formation to produce a "pseudp tck effect." By. studying the pir+ mass distribution forthese events he:. shà.w'edthat.:. peak in this mass distribution near the A 1 can be obtained : by choosing.the events corresponding tothe forward.decay of the 'Nt( see Fig. 15), Thus he achieved by artificial means what the diffraction effect does "naturally" at ip masses above the N band, Whilethis strengthens the Deck model, he. points out that it does not prove that the A 1 is not a meson, -20- UCRL-16744

Seidlitz ej al. 3..2-BeV/c 'rrd

5.0 N (a) (b) (c) C.) -.. 4.0 (p) np0 (n)pp° (p) > 3.0

2.0

1.0 0 rf"1000M0V (d) (e) Ct) 40 H 363 events 2 2 S . eV/c 254 events 165 •vent HI A260.3(BeV/c)2 1080MeV N 30 1310 NOV 4 I30 Nov > w ovo Hey, 1310 NOV 20

w 0. 10 U, 4- C w > ' 0 LI kI &I (g) (h) (I) 0 20 0 0.I5t2 ~ 0.7(BeV/c)2

.0 E z 10

1.0 2.0 3.0 1.0 2.0 3.0 1.0 2.0 3.0 M2 6rp°) (BeV) 2 M26rp°) (8eV) 2 M2(irp7) (BeV) 2

MUB-9789A

Fig. 13. (a), (b), and (c): Chew-Low plots of the iTp systems in the reactions indicated. (d) through (i): Projections of mass squared (Trp) for the same reactions 0 In all plots, events were excluded if neither pair was inthe p interval (600 to 850 MeV). Events with çither nir pair (a), the pTr+ pair (b), or either pirpair (c) in the N' interval (1120 to 1320 MeV) were excluded.

-21 UCRL-16 744

Abolins et al 3.7-BeV/c ir

oI , Meff Of p0 t from the reaction ffl_ pO• 20—

a. All events 10—

C I L.a

0 4, 40 E fbI - b. Eventa with coo a> 0 30— (forward direction)

20—

700 900 1100 1300 1500 1700 1900 M,(MeV)

C. Events with cog a

MUB-9791A

Fig. 14. (left)(a) Effectiye-mass distribution of the p ii combination from reaction Trd-nppp r- ppirir 0 ir. Effective-mass distribution of the p 0 Tr combination from reaction Trd— pflp 0 pnTr ir0 Tr. SolièI curves are phase-space estimates. Broken line is a smooth curve normalized to fit the region outside the A 1 and A 2 masses.

Fig. 15. (right) M ff2 of p° from the reaction Tr +N*p_p+p0 (a) All events (b) Events with cos ct>6 ( forward direction). Events with cos a < 0 (backward direction). -22- IJCRL-16744

(b) He suggestsan additional test for the A 1 phenomenon. In the reaction

+ p - + p + Tr , the decay A1 - p ° + 1TO is forbidden for a T = I meson (Clebsch-Gordan Coefficient = 0) and allowed in the Deck Model, While A1 -'- p - + rr+ is ?Iforbidden?T in the Deck model (exchange of a doubly charged object would be required), it is allowed for a T = I meson, This test may, however, be rather academic, as at the energies investigated so far no appreciable A 1 peak has been observed in the above reaction,

D. A similar test proposed by Kirz A very similar proposal was made by Janos Kirz,' He suggested the study of the reaction

iT +d_ ppAo (3)

is a meson, Here, again if A l + At -'- p+Tr + -'-p +1T -,

i"- p 0 + ir° ,

This reaction has the virtue that it can be quantitatively compared (from I-spin considerations) with the reactions ± ± Trp-'-p+A 1

L o+ ± (7)

Thus Reaction (3) followed by the decay mode (ii) or (5) should be in the ratio 2:1 with reactions (7), while.decay mode (6) is forbidden. On the other hand, on the Deck model, (3) followed by (4) is forbidden; all other reactions are allowed and s e mi quantitative ratios can be obtained for them based on the appropriate i-i-p scattering cross sections. If this test is performed at ener- + gies at which Reaction (7) gives a clear-cut A 1 pe'ak--e, g, for 8-BeV/c i-i- - mesons (if we accept the present data at face value)- -it should result in a conclusive answer on the A 1 phenomenon,

This proposal is quoted by A. H. Rosenfeld, Ref, 13, -23- UCRL-16744

E. The approach by Shen et al.

In our own work with Tr + at 3,65 BeV/c and iip at 3,7 BeV/c

(Shen et al, 30 ) we considered the events with p° production, TT We then asked ourselves the question whether 9 aside from any considerations on A 1 and A2 production, we observe the Drell process, i. e,, scattering of the virtual pion from the proton. We answered this question in the af- firmative based on the following arguments: Let us consider the proton vertexin the Feynman diagram shown in Fig, 16, Here we can look at the correlation between the Tr±p mass for the outgoing particles and the in' gout scattering angle a in the ip p PP rest system. This is shown in Fig, 16a and c. We note two.distinct features: (a) an enhancement of events in the region of the 3/2, 3/2 resonances N' (1238) and N (1238), the latter at about 10% the intensity of the former; (b) a very strong enhancement of events at small scattering angles, cosa 0,8, for both the rr+p and np data, As may be noted from PP Fig,. 16, the cosci distribution becomesmore forward peaked with in- creasing mass of the outgoing iT p system, M(iT p), in a manner characteristic of diffraction scattering. Figure 17 a and b shows the same correlation in three-dimensional plots. To further investigate this effect we have divided the iip mass distribution into four.intervals of width 0 9 25 BeV, starting at 1,09 BeV, These intervals were chosen so that the corresponding differential cross sections represent averages over the various known N resonances, Thus the first interval includes the N' 3/2 (1238) resonances, The next two intervals encompass various resonances near 1500 and 1700 MeV in the irp system. Thelast interval, 1,84 to 2,09 BeV, includes the N (1920) 3/2 resonance, The differential cross sections for the first three energy bands 2 ± 2 are given in Fig, 18 for a A cutoff tothe iT p system of 1.0(BeV/c) It is important to note that this has the effect of virtually eliminating the contributions fromthe A 2 meson(see Fig. 22 below). The corresponding rrp mass projections are shown shadedin Fig, 16b and d. For the mass interval 1,84 to 2,09 BeV our small sample of events did not permit us to eliminate events with A ± >1 (Bell/c) 2 , In order to investigate this mass region as well we have chosen to remove events associated with the A 2 band (1,26 < M ±o < 1,38 Bell). iT p

-24- UCRL-16744

Shen et aL 3.65 BeV/c

pO+.1r+P

1.0 (a (c) .:.;4.,.' •!:A•. . ) 0.4

...... .'...... ..

- . -.. . ....•. ... 0. 0. ...'.. CI • -0.4 0

: ml .f .I • '.

F;TI E pout zi > 0 CO

0 d EG - 00 (I) - C > Ui zi]

Q I 1 1.0 0 1.8 2.2 M(pir) (BeV) M(- pir-) (BeV)

MU B-7770A

Fig. 16. Scatter plots of cos a. versus M(pTr±) for irp and Trp interactions. The mass p?ections are shown in b) and (d) respectively. The shaded regions correspond to E (BeV/c) 2 . The arrows delineate the four mass regions dis-. cussed in the text. -25- UCRL-16 744

Shen et al. 3.65 BeV/c

C 4, 4, 0)

4, .0 z

.0 0.5 0 -0.5 1.0 0.5 0 -0.5

Cos a pp Cos CIPP

MU B-9785A

Fig. 17. Three-dimensional plots of the mass in the Trp and .rr+p system respectively versus cos a pp. This shows how the angular distribution sharpens up in the forward direction as the iip mass increases. ITechnical note: these plots were drawn automatically from the computer output.] -26- UCRL-16744

1.0 E

MWO c

b C%J D 0.01 1.0

Wel

1.0 0.6 0.2 -0.2 -0.6 -1010 0.6 0.2 -0.2 -0.6 -1.0 Cos

Fig. 18. Data of Shen e± al. The differential cross section d 2o/(d2dM) for the four M(pir) regions. Parts (a), (b), (c) and (e), (f), (g) correspond to i 2 (p7r)I.O (BeV) 2 . In parts (d) and (h) no AL cutoff is applied. The A2 band is removed, however. The curves correspond to elastic rr±p scattering cross sections averaged and normalized as discussed in the text. The dotted lines illustrate the exponential dropoff at small angles. -27- IJCRL-1.6744

We have taken two distinct approaches in parameterizing these experimental data, as follows, • a. Diffraction Scattering at the irp vertex We find that the data at small a values can be represented by at PP •+ - the same variation with t, namely e , which holds for Tr p and TT p scattering on the mass shell, We find that the a.+ and a values for "virtuaP' and Tr p scattering lie in the region 8 to 1.2 (BeV) 2 , The dashed lines on the semilog plots in Fig, 18 indicate that at small angles a good fit can be obtained with an exponential dropoff, b. Comparison with fëlastic Ir±p scattering experiments

Here we have taken the available experimental Tr. p and irp. elastic differential scattering cross sections fromcounterexperiments and have averaged these over the four mass intervals.specified.above, i,e,,

M. / dff \ thr el el . -,M .), f dM/(M i \dc2/ M. d2 3 i

We have compared these distributions with our experimental distributions by normalizing the elastic differential cross section to the experimental points in the cosa region 0,8 to 1., 0. We find that the general PP shapes of our experimental distribution, although sonewhat more peaked dael near a = 0, are remarkably close to the distributions of We pp d2 conclude that here, unless one were to ascribe this feature to some acciden- tal effect, we have experimental evidence for point (e) in SectionIIIA, We now turn to the question of the A 1. and A2 "mesons," which are observed as enhancements in the Tr± p ° system. If we limit ourselves to the sample of events primarily associated with diffraction scattering- -i, e, cosa0,8 and M(pTr±) 1.,34 BeV--we find a broad enhancement in M( Tr± p 0 ) , • with evidence of peaking at the A 1. and A2 bands, Aside from a small A 2 contribution this mass distribution can account for the entire A 1.enhancement observed in our data see Fig, 1.9a, On the other hand, eliminating the • events associated with diffraction scattering- -i, e,, cosu pp < 0,8, and ± leaving the same condition on M(pir )- -we remain with a clear A 2 peak (see Fig. 1.9b), whereas the A 1. peak has completely disappeared. -28- UCRL-16744

Shen et al. 3.65 BeV/c r t

a) 0.

U) 20 C a) > Ui

1.1 1.5 1.9 0.7 1.1 1.5 1.9 2.3 M (p° ir t ) ( BeV)

MU B-7769A

N*++ Fig. 19. The M(1T p° ) mass distribution with the band removed. (a) Distribution for cos a 0.8, i.e., for the events we have associated with Itcliffractioncattering.ht (b) Events with cosci 0.8. pp -29 - IJCRL-16 744

Here we must remark that the condition cos >0,8 is of course 2 . pp equivalent to small z (A 1 ) values, Thus, although our evidencemakes •interpretation as a ,diffractionffect very tempting, . it is not the only possible interpretation. We now turn our attention to.points.(a)through (d) (in Se.ction.IUA), the alignment of the p° and the Treiman-Yang angles at the two vertices. These are studied for the A 1 band and the A 2 band as a control region. The results are given in Figs. 20a and b and 21. We note the following:

The p° is indeed strongly aligned, for the A 1 band, although not for the A 2 band(see Fig. 20a). Another noteworthy featu.reis tht the asymmetry familiar in p° decay is observed here for the A 1 although not for the A 2 band, The Treiman-Yang (T-Y) angle at the p° vertex (p ° ) lis isotropic for the A 1 band; however, it is also essentially; isotropic for the A 2 band, It thus follows that the T-Y angle does not appear to be a stringent test.in this instance (see Fig, 20b), The Treiman-Yang angle for the irp vertex (piT±) is strongly an- isotropic for the A 1 band.(see Fig, 21), At.first sight this; looks bad for the kinematic enhancement model.

There are, however, the following two mitigating factor s:

(i); As illustrated ini Fig, 21, on introduction of the Tir p mass cuts (to delineatethe A 1 andA 2 bands), the system appears to beoverconstrained, That is, as may be noted.from Fig, 21, we find a definite correlation between (p7r±), the Tr p ° mass cut and the distribution in As a furthercontrol we have carriedout the same Tr±p0 mass cuts for p0N*++ events, which again show the same correlation, . Inparticular,' the p0 N events adduptoan isotropic distribution (as expected) when all mass cuts are 'dombined.to. give the 'TTotal' distribution shown in Fig, 21. .

JI This figure differs from the one shown. in Ref. 28; the one given here is correct while the one in Ref. 28 includes events in the N band as well. There is, however, no qualitative difference between the two, thus all con- clusions.reachedin Ref, 28 remain unaffected.

-30- UCRL-6744

3.65 BeV/c lr±p Shen et aL

+ p p0 + 7r± + p

N* out

A 1 band A 2 band

OCosa ~ O.8 - DCosaO.8 PP

C a) > a)

0 a) .0 E = Z 20

C C) a) 20 0

a) .0 E = z D

-r

0V////V///////4////,I 0 90 180 270 3600 90 180 270 360 1,00) (deg)

MU 6-9812

Fig. 20. (upper) Distribution of cos a, the Trrr scattering angle in the Tr p° c. m The data shown are selected with 14 p ° mass in the A and A2 bands respectively and for (Tr±p) ut masses above the N(1.238) band. (lower) The corresponding 'freiman-Yang angular distribution.

-31- UCRL-16744

3.65 BeV/c irp Shen et at.

lr±p_p0 ,r±p N* ou t DCos a pp ? 0.8

(-0.98) (0.98 -1.10) (1.10-1.22) (1.22-1.34) (1.34-1.46) (1.46-1.58) M (p°ir t ) (6eV) 60

40—

0 l800 0 1800 0 1800 0 18000 1800 0 1800 —Al band - --- A2 band -

(1.58-1.70) (1.70-1.86) .,. , (a)

200 40 4(pr±)

W 00 p,..JJ;Z1 '°:___ 180° 0 1800 0 1800 .±p.._...pON* (for control) _ 60 (-0.98) (0.98-1.10) (1.10-1.22) (1.22-1.34) (1.34-1.46) (1.46-1.58) M (p ° ) (BeV)

-LLL, 0 r 0 1801 0 1800 0 1800 0 1800 0 1800 0A 1800

(b) Total (1.58-1.70) (1.70-1.86) 200 40 -

100 20

0 0 0 180° 0 180° 0 180 0

MU B 9 834 A.

Fig. Zi. The Treiman-Yang angular distribution at the outgoing 1rp vertex. (a) Distribution drawn for a selection of M(pii±) mass values to illustrate the correlations existing between this mass and the Treiman-Yang distribution. (b) The same distribution for p ° N events used as a control region. -32- •UCRL-16744

(ii) When we limit ourselves toevents with cosca 0,8 (which enhances pp , the A 1 phenomenon), shown shaded in Fig, 21,. the 4(pir ) distribution is nearly consistent with isotropy in the A 1 band,

We thus conclude that the T-Y distribution at the rr±p vertex must be handled with extreme care, When this is done the data do not appear to contradict the "kinematical enhancement" hypothesis.

(d) In Fig. 22 we show the A2(0) distribution- -the four-momentum transfer to the p meson0 The distribution for the A 1 band is narrow, the peak extends to Z(0) ;3ODkn'--however,. not so narrow as for p0N++ events, for example (not shown here). In the latter casethe peak extends to 2(O,) i.üm2n. A possible interpretation of this differenceisg0iveinhim':terms of the kinematical boundary imposed by the Chew-Low plot, This is shown in detail for K**(1320) below, On the other hand, for the A 2 control band we observe a double "hump" in the i2(p0) distribution, where the second hump' (L2 p0) = 40 to 80irn2 is associated with the A 2 meson, Thus the AZ( O) distribution for the A 1 bandmay be considered "consistent with the OPE model." For 2 2 completeness we also show A (p), which equals the A to the p ir system, for the A 1 and A 2 bands(see Fig, 23), If we expressthese in the form ewith t = (p), then we obtain a(A 1 ) = 8,3 (BeV) 2 , and a(A 2 ) = 3.0 (]3eV),

From all the evidence presented here weconclude that the ' 1 A 1 enhancement," as observedin our data, is consistent with what is expected from the diffraction scattering of virtual pions, F. New results from the experiment with 16-BeV/c ir on Freon 32 Allard et al, have been able to show from a study of the four- momentum transfer distribution that there is an initial steepsiope with t, which they associate with coherent production, followed by a more gentle slope which they associate with noncoherent production (see Fig, 24a). The coherent production gives rise to the A l phenomenon ekclusively, while the noncoherent production gives the A 1 with the possibility of some A 2 production as well. Figure 24b shows the cross section for the coherent production as a function of the pion rnutlipliáity. This indicates the great preponderance of 3rr production,

-33- UCRL-16744

Shen et at. 3.65 BeV/c ir p ...... p01T±p

I I I I I 40- lrt+p _._spO+n±+p

0.98M(p)I.I8BeV 30- 234 events, N*++ out E

LC A c'J 0 0 50 100 a) 2( 0. (m,-) IC 30 C E 4) In > 4) w C 0 U, C 30 4) a) > D LU 20 I.22M (pw) S 1.42 8eV E D 4 z 20 322 events, N*+ out

A2 to E

C0_I 160 20 30 If

2 (p° ) (m) 2 00 50 100 ISO (m.)

MUB - 9880A

Fig. 22. (left) Momentum transfer to the p ° for the A 1 and A2 bands respectively.

Fig. 23. (right) Momentum transfer to the p ° Tr system for the A 1 and A 2 bands respectively. -34- UCRL-1.6 744

6 TO 18 GeV/c ir INTERACTIONS WITH NUCLEI

Orsav-Ecole Polytechniaue-Milan-Saclay-Berkeley Collaboration

(a) 7rp el. scatt. 0Lo 4. 10

16 GeV/c 7T7T7T

r. 0 1 0 3 0 0

6 cV/c rir 0 0 102

2 3 4 -+-+ Pion multiplicity 1 I H 16GeV/c 77 77 i 77 0 0.1 0.2 ttt m

MU B - 9879A

Fig. 24. (left) Logarithmic plot of da/dt vs t, where t'=t-tmjn. Lines (a), (b), and (c) correspond iespectively to 1/t0 = 9 (GeV/c) 2 (irp scattering), 54 (GeV/c) plus a background of 7 (GeV/c) 2 (rrFl+ rrn scattering + experimental resolution, least-square fit to data), and 84 (GeV/c) plus a background of 7 (GeV/c) 2 (rrC+irn scattering + experimental resolution, least-square fit to data). (right) Cross setion vs pion multiplicity for all channels of charge -.1. and t< (2m) for incident rr of 16 GeV/c.

-35- (JCRL-16744

Huson, as spokesman for the group at the 1966 New York Meeting, 33 also showed the angular distributions they obtain for the p ° decay (see Fig. 25). The results are very similar to our data. They find a very strong alignment of the p° from the A 1 "decay. 11 which gives a cos 2 distribution together with the well-known forward-backward asymmetry (see Fig, 25a), an isotropic T-Y angle distribution at the p° vertex (see Fig, 25b), and non- isotropic T-Y distribution at the nucleus vertex (Fig, 25c), The latter distribution was cited by Huson in New York as evidence against the kinematical enhancement hrpothesis. However, more recently 34 the feeling is that this can perhaps be due to contributions from the. noncoherent scattering, for which the system may be overconstrained, just as we show for our data above. Furthermore, they give the angular distribution of the 'bachelor piOfl in the A 1 center of mass with respect to the incident pion (Fig, 25d), This is the same distribution as we show for our data in Fig, 33 below (see discussion in Section VI,2), Finally, they give the distribution to the p° which they feel is too wide for the OPE model (see Fig. 26), and this together with the narrow width of the A 1 peak, represents at present the only evidence they cite against the kinematical enhancement hypothesis.

G. Compilation by Ferbel An interesting compilation of all available and np data was carried out by T. Ferbel 35 (see Table I), He tried to see to what extent the A 1 , A2 , and B effects show up if no preselections (such as p or w produc - tion, and N++ eliminated) are made. He compiled data from 2,75 to 8 BeV/c, on two reactions, ± ± - Tr + p - r + p + iT + + iT , 28,700 events . (a) ± ± + 0 and 11 + p - iT + p + ir + ii - + ii , 26,300 events. (b)

His results are that although the A 2 meson persists clearly the A 1 and B "phenomena" are "washed out" to a large extent (see Fig, 27). The results on the B phenomenon are not surprising, as it never showed up noticeably without w selection. What is particularly relevant here is that the "washing out" of the A 1 peak may indicate small displacements in the peak position in the various momenta compiled. This result favors the kinematic enhancement interpretation for the A1.. -36 UCRL-16744

Berkeley-Milan_Orsay_Saclay 16-GeV/c r, heavy liquid

80 QA'150 MeV/c - all events (641) (a) - - - " A 1 events" (260) (b) 120 40 t H 80

-1.0 cos 9 - - 1.0 00 180° pbeam T-Y (p) I 60 (pc.m.) -

40 14 JI.HLJL :: Tr lSoveJ

0 I .0 180° L0° - T-Y 1.0 100 80 60 40 20 0 (Nr) -1.0 cos 9 - rBachrbeam L2(pP) (p2) (A c.m.)

MU B-9882A

Fig. 25. (left) New data from the ii on nuclei experiment. (a) The irir scattering angle in the p° c m. (which is called cos a in the text). (b) The Treiman-Yang angle at the p ° vertex. (c) The Treiman-Yang angle at the ir-N vertex. (d) The angular distribution of the p° (what is actually plotted is the Thachelor pion" direction) with respect to the incident pion in the A center of mass. Dashed curves correspond to the "A t events.t'

Fig. 26. (right) The momentum transfer to the p°. The dashed curves correspond to the A 1 events. -37- rJCRL- 16744

Table I. Sources of the data compiled by Ferbel,

Momentum Range and references Number of events (BeV/c) Tr + Reactions ri Reactions

(a) (b) (a) (b) 3,0 a- e 2990 3000 5170 3900 3,,0to4,0 'f-i 5450 5700 6870 7020 4,0 i-n 3840 1800 4420 4900

Total 12280 10500 16460 15820

a, N. Gelfand et al. • (Columbia-Rutgers collaboration), B. S. S. Yamamoto et aL (Brookhaven National Laboratory ip collaboration), , J, Alitti, J. P. Baton, et al. (S. 0. B. B. d. P. R. Klein, G. Taütfest, et al, (Purdue ip). ë. Hagopän, W. Selove, et al, (Pennyslvania ip). f', Moebs, J. C. Vander Velde, et al. (Michigan Tip). g. G. Goldhaber, S. Goidhaber, B. C. Shen, et al, (Berkeley 1Tp). 1. A. bIins, P. M. Yager, N, H. Xuong, R. L. Lander, et al, (La Jolla i. S. U. Chung, D. H, Miller, et al, (Berkeley 'p) , .j). A, B,B, B,.H, L. M. iT+p Collaboration, Phys. Rev, 138, B897 (1965). k, M. Cason and M. L. Good (Wisconsin up). P. N, P. Samios et al, (BNL-CCNY up collaboration). a-n. K. Lai et al. (BNL-CCNY up collaboration) + .. D. R. 0. Morrison et al, (A. B, C. Tr collaboration).

OWE UCRL-16 744

Compilation by T. Ferbel irp 2,75 to 8 BeV/c

I I I I I I - 7r±p.p.77±p 71 + (a) 7T ± P+7T± p - 7T 7T 710 (b) Aa 7OO EVENTS - 26,300 EVENTS 20

0 1- B Of

C') CO I- I F- I Z >1w w 1 U L. 0 0

w U

500 1000 1500 MASS OF 71± .fl 7fl (MeV) MASS OF 71± -7r77- 7r°(MeV)

MU B-9793A

Fig. 27. (a) The iT±r+1T mass distribution comiled by T. Ferbel without any selection criteria. (b) The irrr Tr — Tr 0 mass distribution compiled without any selection criteria. -39- UCRL-16744

H. A Test proposed by A. S. Goldhaber 36 The following comment was made by A. S. Goidhaber. He pointed out that if the A 1 is a meson and consequently a state of definite spin and parity, the p meson obtained from A 1 decay should show no forward-backward asymmetry (in the angular distribution of p° decay) with respect to the incident direction when observedin the A 1 center of mass. It turns out, however, that thetransformation to the p0 center of mass does not change the angular distribution drastically, thus even this distribution (in cosa) should not show an asymmetry. The experimental data, both in our experiment (see Fig. 20) and in the heavy-liquid experiment (see Fig. 25), however, show a very marked asymmetry! The sign and magnitude of the asymmetry are the same as observed for essentially all other sources [no asymmetry in p° decay is observed in the photoproduction process y + p - p 0 + p ( Ref. 37).] of p° production by charged mesons. Although one can always invoke interference with a suitable background as the cause for the observed asymmetry, this result favors the kinematical enhancement hypothesis for the A * Although the asymmetry in K (890) decay is much less pronounced 38 than for p 0 decay, a definite effect has been demonstrated. Here again some asymmetry is obtained for the K(890) production from K*(1320) decay" (see Fig. 29 below),

V. THE EXPERIMENTAL RESULTS AND TESTS ON THE K(1320) PERTAINING TO KINEMATIC ENHANCEMENT

All the arguments and graphs we gave for the A can be repeated here for K(1320). We will.just present the corresponding figures from our 4.6-BeV/c K+p experiment with very few comments. Figure 28a shows the Dalitz plot for all K events from Reactions(1) and (2). In Fig. 28bwe show the scatter plot for these same events of M 2 (pir) versus cosct . From - PP this it can be seen clearly that the K (1320) band corresponds to the

Simi1ar results on some of these angular distributions have been obtained by the group at Oxford from a study of the K p interaction. (private communication from D. H. Locke to S. Goidhaber). Graphs on their work are, however, not available to us at present. -40- UCRL-16 744

p -' Kir+ p 4.6 BeV/c 689 events .i 6.0 (b) > CO 50

-a 4.0

N 3.0

I 0.5 1.5 2.5 3.5 4.5 5.5 -1.0 -0.6 -0.2 0.2 0.6 1.0

M 2 ( K ir) ( BeV) 2 Cos a in (irp) cm. PP

K+p K*O+ ir+ p 4.6 BeV/c 560 events I (1.091.34BeV) ,150r 0.84-2.09BeV) 10

10 Cn

-H

(2.09 - 2.34BeV) -10 (1.59 - 1.84 BeV) E 5- .5

Oil I I I I 10.1 1 h I I I 1.0 0.6 0.2 - Q2 -0.6 - 1.0 1.0 0.6 0.2 -0.2 - 0.6 -1.0 Cos app in (irp) cm.

MUB-9786 Fig. 28. (a) The Dalitz plot for all Kirp events from the 4.6-BeV/c data. This corresponds to the sum of the Dalitz plots shown in Fig, 8. (b) The same events as in (a) shown in a scatter plot of the M 2 (irp)vs coci. . The comparison between (a) and:(b) indicates that the Kirjhancethent corresponds to the observed enhancement at small a scattering angles. (lower) The cos distributions for a sele?ton of 1T+p mass bands similar to Fig. 1 which is drawn for the A 1 phenomenon. The curves shown come from the available counter experiments averaged 2over the energy intervals indicated. In the plots shown here no A cutoff was taken. -41- UCRL-16744

small-angle band (cosa pp z 1), Figure 28 also shows the d 2 a/d2dM distribution (in arbitrary units). These are compared with the experimental curves for dg el This figure is the analog to Fig, 18, corresponding to the point (e) in Section hA, Figure 29 shows the cosaKK distributioninthe K center of mass and also the T - Y distribution at the K vertex for events in the K'(1320) band, Also .shownas a. control region are the same distributions for K ° (890) N*++ events, As expected on the Deck model, the two sets of distributions are very similar. Figure 30 gives the T . -Y distributionat the vertex. Here againthis distribution isanisotropic, where.the.an- isotropy is associated with the Kir mass cuts. The same distribution for the K' ° N events, here shown as a control region, also gives this correlation, In Fig, 31c we show the A2 (K) distribution for events in the K (1320) band, At first sight this distribution looks too broad for the OPE * model, say, when compared with the control region for K N *++ events in Fig, 31d, A possible explanation forthis broad distribution is, however, quite straightfcrward0 It becomes clearif we look at the Chew-Low boundary calculated for K np production [using M(K)min = 840 MeV, the lower limit of the K mass band] in Fig, 31a, Thus the events with high masses which contribute appreciably to the KC(1320) band, are forced by the kinematic boundary to lie at fairly high A 2 (K') values, while the.events in the N band (Fig, 31b) are not so constrained. Finally, for completeness we also give (p), which is the same as -at the z 2*to the K n system, If we represent this in the form e , with t =2(p), . then we find a(K"') = 6,7 (BeV), Here we must stress that the boundary shown.in Fig,. 31a corresponds.to the minimum. values' of the K mass, If we draw the boundary forthe "maximum value" (940 MeV, not shown,here) it comes much closer to the points at high M(pir) values, All the same, even a distribution in

Z (K) - (K•)min remains slightly broader.than for KN events, where 2 (K). is the Chew-Low boundary value for a given event [i, e.,, a func - tionof M(pir) and M(Krr) forthe event],

-42 tJCRL-16 744

4.6BeV/c Kp.

I I I I I I

30 p p K*Ot N*, 74 events 1.24 :5 M(K*Olr+) 5 1.40 BeV ItO events out 30 (Control) T U) (a) (c) a) 20 L > ci)

4- EPZOI 0

ci) -Q 10 E z IIIIIIIIHII

O'! //,I'/i/ I// /V//I 0 V/A/ /A'//I/,I //A -1.0 -0.6 -0.2 0.2 0.6 1.0 -1.0 -0.6 -0.2 Q2 0.6 1.0 Cos aKK in K*O c.m.

I I I I

K++p__..K*Os .+-- p 1.24 :5 M(K*O77$):5 1.40 BeV 174 events ItO events I 02 (K) 25m out (Control) (d) 20 (b) I

; 10 -Q

z n "0 90 180 270 3600 90 180 270 360 4) (K) (deg)

MU B-9811A

Fig. 29 (a) The KK scattering angle ii the K*o center of mass, and (b) the Treiman-Yang angle atth be vertex; (c)and (d), corresponding distributions for the KN events.

-43- UCRL-6744

4.6 BeV/c Kp

Kp ___.K*°. r t p N+ out L K+,r O

M(K* lr ) (BeV) - (1.0-1.24) (1.24-1.40) (1.40-1.64) (1.64-1.84) (1.84-2.16) Total 40 80'-

20 4H0 U) 4- cO 0 18000 >W 180. 0 180° 0 180° 0 1800 0 1800 W K**(1320) K+p__._K*O N* (for control) 30 LK+ irp To to I W 20 40 1- .0 E z 10 20

00 1800 0 1800 0 1800 0 1800 0 1800 0 1800 (pir+)

MU B-9831

Fig. 30. (upper) The Treiman-Yang angle distribution at the proton vertex. The distributions were drawn for a selection of M(p 0 mass values, to illustrate the correlation between this mass and th Tçeiman-Yang distribution. (lower) The same distributionfor K4ON events used as a control region.

-.44 UCRL- 16 744

Kp Krirp 4.6 BeV/c

0 50 100 0 50 100 ISO.

N*ba:d+

(a) 30

+p 1 K+ p K* ir 60 I N' out p 10 K**(1320) band N* band Mt E 85 events 174 events LO 40 (c) (d) 0

U, 4- a, > a, 20- 0

01 0 0 50 100 0 50 2(K*) (mw)

MUB-9835

Fig. 31.. Distribution of the four-momentum transfer to the The Chew-Low plot shwnin (a) indicates how the boundary forces the events to higher A (Krn) values

-45- IJCRL-16 744

Data presented by Dornan et al. at the 1966 Washington Meeting is of particular relevance to the subject under discussion here. Dornan et al. studied the Kp reaction at 4.6 BeV/c,

In particular they observed K'(890) + 11 production in the reactions

Kp - K° rrlT ° p (8) — -+ - KlriTn,o (9)

JI In these reactions K (890) production occurs according to

Kp - R*ThTOp (8a)

JI - R ° ip (8b) (9a)

These reactions differ markedly if interpreted in terms of the Deck Mech- anism. In Reactions (84) and (8b) we can consider the lone pion to undergo diffraction scattering at the proton vertex; however, in Reaction (9a), on this model, the exchange pion must undergo charge-exchange at:the prcton vertex. This tends to reduce the cross section very considerably. The experimental JI data (see Fig, 32) indeed shows a very considerable peak in the K(890) ir mass distribution near 1320 MeY for Reactions (8a) and (8b) combined, but not for Reaction (9a)! On the other hand, evidence for R(1400) -* R(890) + ir is observed in both reactions. These data thus strongly favor the kinematical enhancement interpretation for the K (1320), Although one might be tempted to close the subject right here, there is one "but" left to the ITmeson hypothesis. ' All reactions other than (9a) leading to K (1320) production (considered now as meson) can proceed via isoscalar exchange, whereas Reaction (9a) must correspond to iso- vector exchange. If for some reason the latter is strongly supressed relative to the former, one could also explain the data shown in Fig. 32 on the "meson hypothesis.'T -46- tJCRL-16 744

60 DORNAN ef al. Kp 4.6 6eV/c

O o - K - I I p < 0.5 (BeV/c) 2 0.84

> 20 ci, 0 I') 0 0

(I, C 0 /2 1.0 1.4 1.8. 2.2 0 M(K ° irir) (BeV) a) 0 E 40 Kp —n K r + 7r_ 11 t 2 p<0.5 (BeV/c 2 0.84< M(K ° ir)< 0.94

i-i - S]

0 I I 1.0 1.4 1.8 2.2 M (K 0 *ir) (BeV)

MUB-10711

Fig. 32. Results of work by Dornan et al. (Reference 39).

J4.. rJCRL-16744

VI, THE ARGUMENTS IN FAVOR OF AN A 1 MESON AND K'(1320) MESON -

1, Spin assignhient from the A 1 Dalitz plot

As pointed out by Zernach and Frazeret aL ,41 and:from the numerical evaluations by Diebold, if we are dealing with a definite 11p state the J value can (in principle) be obtained fromaDalitzplot. Figure 33 shows the data of the 8-BeV/c experiment 7 and the 16-BeV/c ir on Freon experiment 1 relating to this question. These results favor the assign- J P = ments it with 2 as a less likely possibility, 2. Leith s argument favoring a JP= 1 + A meson 1 During a seminar by one of us at CERN (October 1965) on our A 1 data, D Lith43 pointed out that the observed alignment of the p° from the ..Al band with the incident direction could also come from a i meson. He makes the point that one could have A l production (considered, here as a + J P=1 +meson) by a.diffraction effect involving the exchange of a•0 'tobject' or the vacuum trajectory on the Regge formalism, This would lead:to an • alignment of the A l , since it would be produced from a collision between a 0 meson and a 0+ "object" in a relative p state. The argument is identical to the alignment obtained for a p° "meson in virtual pion exchange. Next the A 1 decays through an s wave into a p ° and iT. Thus the p ° would carry the same alignment as the A 1 and hence would show the characteristic cosa 2 distribution we observe. There is afine. point involved here, namely the A 1 is completely aligned in the A 1 center of mass, while center of mass. The transformation the p 0 alignment is studied in the p 0 between the two centers of mass..;is such, however, that the alignment, is not appreciably altered. This also applies to the 'T-Y angle at the p ° vertex,

which, . strictly speaking, would be expected to be isotropic only for the' A l • polariz.at±n::. vector in the A center of mass, ' l Thus this model would satisfy conditions (a) and (b) of Section lilA, Furthermore Leith argues that our data indeed correspond primarily to dif- • .fractionscatteringof the virtual pion, as wehave suggested, andthat theA 1 meson is superimposed on a considerable background. Thus all other observed features remain unaltered,

-48- tJCRL-i6744

AACHEN -BERLIN -CERN collaboration 16 GeV/c on Nuclei AT 8 GeV/c. ECOLE POLYTECHNIQUE, CERN, MILANO, SACLAY, U.C. BERKELEY 0.95 (rrTir) MASS 1.125 GeV q < 150 Mev!c 1A IZI- 1.0 • EACH EVENT PLOTTED TWICE

125 EVENTS I I Al L

PROJECTION OF / 3 1.0 RHO BAND 01 02 - 03 0.4 05 0 0.7 0.8 0.9 201 0-

01 01 02 03 0.4 0.5 05 0.7 (18

2 +- 2 MT1T)(1 (GeV) M 2 (Tr1T) (GeV) 2

MU B-9795 A

13,

Fig. 33. The Dalitz plots for the A1 . These show the evidence for spin assignments if the A 1 is considered a meson. -49- rJCRL-16744

Finally, on Leiths model, since A 1 decay into irp (and similarly ** * + K into K ii if this is also considered as a 1. meson) proceeds via an s wave,, the distribution of the p° in the A 1 center of mass should be isotropic relative to, say, the incident Tr direction, In Fig. 34 we show this distribution for the A 1 and K bands (as well asthe A 2 band forcontrol), Figure 25d shows the same distribution.forthe heavy-liquid experiment. As may be noted, the distributions are not far from isotropic, although they appear to have a small cos 2 component present. Thus here again it becomes a quantitative question as to how much background and how much of the A 1 [or K(1320)] meson is present. No definitive conclusion can be drawn on the basis of presently available data, 3. The sharp A 1 peakin the 8-BeV/c data

As shown in Fig, 4, the A 1 peak observed in this experiment is very sharp, and as such is suggestive of a bona fide resonance. There are, however, two questionsto be answered: (a) Why isthis effect not so clear in the 6-BeV/c ip data? (b) To what extent can we believe the OPE cal- cualtions by Wolf44 (unpublished) for an accurate background subtraction? Does one really know how to calculate the OPE model (including Bose symmetrization) for higher spin resonances, such as the N 12 (1920) in this case? 4, The Sharp K (1320) peak in the 4,6-Be.V/c K p data In our data 11 (see Fig, 8) we also observe a rather sharp Kir peak. But the same criticisms applied to the A 1 peak apply here as well: 12 + (a) Why do the data of Jongejans et al, (at other incident K momenta) not show such a sharp peak? (b) We do not know the accurate detailedshape for this peak to be expected from an OPE model, One small point here, which favors the 1 meson" hypothesis, is the location of the peak. From the OPE calculations (e, g., Maor and OHalloran) one obtains an expected mass of = 1200 MeV for such a peak. This is also the value obtained from a crude order-of-magnitude estimate in which we consider that on an OPE model the HQ value for A 1 n + p should be the same as that for

it + K, Thus the.experimental value of 1320 MeV is about 100 MeV * higher than the OPE value, As mentioned in (b), however, it is conceivable that there is that much leeway between the present-day OPE calculation and a 'correct calculation,

-50- tJCRL-1.6 744

3.65 BeV/c 7r±p Shen et al. 4.6 BeV/c Kp

K+p_K*,r p polr±p N* out N* out K**(l320) bond

(a) (b) 134 events

A l band A2 band (c) 233 events 321 events 211 U, 4-

a) 20 ID]

I I I I I I I .01 I I I -1.0 0 1.0-1.0 0 1.0 -1.0 0 1.0 ** Cos a (ir 'Pout) in Acm Cos a (Ki n K u t) in

MU B-9832A

Fig. 34. (a) and (b) Angular distribution of the p° with respect to the •incident direction in the A center of mass for the A and A 2 bands. (c) Corresponding distribution for the K(89O) in the K(1320) center of mass. - 51- IJCRL- 16744

VII, 'COHERENTt' p ° 1T AND k'rr PRODUCTION ON DEIJTERIUM

There is a recent series of experiments on the 1T D interaction and KD.interaction which have observed p ° Tr production and K0ir+ production, respectively, .without deuteron breakup:

11 U p 0 ir Kd -

The experiments are:

nD at 32 BeV/c Miller et al. (Fig. 35), 'lTD at 3,7 BeV/c Abo.lins et al, (Fig. 3),

iT +D at 6 BeV/c Vegni et al, 7 (Fig,. 37), and our own experiment,

K + D at 2,3 BeV/c Butterworth et al, 4 (Fig. 38),

These experiments show a.number of features of relevanàe here.

a. In each of the experiments, p 0 (or K) production is the dominant process [from 80 to 100% of all iT ii. iT .d) events.]. See the ii. i (or K iT distributions in Figs. 35 through 38, The p° and K'are observed to bealigned.inthe respective experiments (see Figs, 35 and 38). The respectiveexperiments show p0lT± mass peaks and aKTr mass peak which are verybroad. The p ° ii data do not rs'hw. any. A 1 or A2 structure, neitherdoes the Krr peak show a .K1320) structure .(see Figs. 3 .through 38). The location of the A 1 and A 2 peaks hasbeen mdi- cated on Figs. 35 through 37.

The mechanism by which these reactions occur-is not fully, under- stoodat present. There are threepossible mechanisms we.can consider:

(a) In each of the reactions observed, p 0 Tr (orKii) productionwith deuteron breakup is an important channel. The observed data may. thus correspond to the very, low-momentum-transfer end.of these reactions (possibly even with pn recombination to form a deuteron). In this case the deuteron (without breakup) is acting as a 'momentum transfer filt er t which ensures small.momentum transfer to the deuteron and consequently to the -52- tJCRL-16744

Miller et al.

3.2-BeV/c r d-. p 3.6 - °iTd

(a) (b) 3.2 -. . ::.

> ... . o . •... 2.8 -. ••. .. . + ..

A(fO8O

- (s. 2.0

2.4

2.0 4 is 0 EventsA per 40-MeV. inlervol ... 0 fi (f) H 40 263 events 50 H . C - I ILower'(..-)poirs Ii 30 0 -.. HiherA(.v.-)pofrs -2011

250 450 650 850 050 1250 1450 -1.0 -0.5 0 0.5 M - - (MeV) iT + IT iT M(...-( (Mcv) Cos(..(

MUB-1019j.

Fig. 35 (left) (a) — (e). Scatter plots and effective-mass projections for +d_ed+7r++7r+ rr. The scatter plots include only the c?mbination 7rirL (d) and (e) include also the combination (see text). (f) The distribution in-cos 0 of th angle between the incident ion and the outgoing ir in the (ir ir) center of mass for both A (in) combinations. (right) The effective- mas distribution for the three pions in the final state, d+in +7r+7r

UCRL- 1. 6744

20 Abolins et al.

(a) 0— 3.7BeV/c Tr . dpd

000-

...' 600

•. ,

I I 0 0 0 2000 2400 2800 3200 3600 Mld.)U.V

20 (bY 10 A 1 ( 108 0) . I 2200 N

1400

... 0

1000 c=çJS •_ I

0 0 0 0 2000 2400 2800 3200 3600 4000 N I&ld.1U,V M(3v) MaY

MU B-10192

Fig.. 36. (left) (a) Histogramof the d-Tri mass versus Trz Trmass Each event is plotted twice. (b) Histogram of the d-...mass is the r versus ir— ir mass. Each event is plotted once. + which gives the lower momentum transfer totie Tr - combination. The reaction studied was Trd-1rr rrd, but led primarily to p ° Tr_d formation. (right) Distribution of effective mass of the three pions; all events. tJCRL-16744

Fig. 37. (left) (a) . Distribution of the quadrimonentum rnsfer t to the deuterium; solid line: 251 events that fit i d - dTr 'rr ii. (b) Distri- bution of the square of te tranvrse momentum q 1 given to the deuterium in the reaction ir d - cFrr ii 'rr; solid line: the 251 four-prong events, a+nd± the 56 three-prong events (shaded events), fitjng ir d - d iT n- .; dashed line: the four-prong events with M , rr+d 2.35 (GeV/c) . The expone tial fits to the graphs are made over the interval 0,02 - 0,1 (Ge\T/c) for (a) and (b) and over the interval 0.0 - 0.1 (GeV./c) 2 for (c); For comparison, on (c), the corresponding lines have been drawn for radii of proton (R = 1.1 F.) and of carbon (R = 3,24 F ). (c) Distribution of the quadrimomentum transfer t to the deuterium of 570 elastic iT+d events, corrected for scanning bias (preliminary results), (right) (a) Effective mass of the three pions in the reaction ii d - d 1T+1r, haded events are the ones with M( Tr+d) < 2,35 (GeV/c) 2 . (b) iT 1T effective-mass distribution, each eveit plotted twice. Dotted events are the cor4ibinations which give a ir Tr mass further fron the p mass, (c) TrA1T invariant-mass distribution, taking the iT which, associated with the duterium, leads to the lower quadrimome4itum transfer to the system iT d. Dashed events are the ones with M (ird) < 2,35 (GeV/c)2. -55-. UCRL-16 744

A1(1080)

- 0 + Vegni et al. 6_BeV/c ir + d .p r d

160

100 ... 00 _SLOPE b• -32.7. 6. 20 lG.V/c)

40 40 400 752

(a) Tél 20 20 200 (c) c'J 0

0 0 10 100 8 .8 1.0 1.5 ao 6 6 M(,r,r,r) (6eV/c)' 0 C 4 4 40 LO 70 2 2 20 60 (c) a) > • 0 Iv .1 .2 . 0 .1 .14 0 .1 .14 50

t(GeV/c) q ) (GeV/c)' t(GeV/c) 0 251 events C 40

0 .4 .8 1.2 160 .4 .8 1.2 1.6 Mnir1 OeWcj M(ir7r) 3eV/c

MUB-10193 UCRL.-16744

+ Fig. 38. (a) Md + vs MK+ - for the reaction K .+ + d-'- K + + iT- + iT + d, with projectins, For The M + projectionthe haded histogram shows the distribution for events wiJ MKOTI.+ in the K region (0.84 to 0.96 Bev). The soid and dashed curves showphase space for K+d-'K+r+Tr+d and K+d-"K+'rr+d, respectively,rormal4zed to+the appropriate number of events, (b) The reaction K. +d-K +Tr+rr. +d, Distribution of cos aK = (IKi n' K ut/KirioutD the cosine of the KTr scattering angle in the KiT center ofiass, for events with 0,84 MK Q2,96 BeV, (c) The reaction K +d-"K +ii+i. +d. Chew-Low plot of'nKTrTr vs MKTrrr The s9lid points are for events with 0.84< Mv+iT <0,96 BeV, i. e,, in the K region, Those marked X are for events outside this region. Shaded histograms refer to the former events. The smooth curve on the 2 projectiqn shows phase space for K+d-K+iT+iT+d, the dotted curve tha!t or K+-"K+iT+d. The dotted line joining the two projections shows that MK would have to be less than 1, 8 (BeV) 2 if the "momentum- transfer Iter"1 produced by the deuteron form factor were approximated by a sharp cutoff at 0,2(BeV)2, -57- UCRL-1.6 744

ButterWorth et al. : 2.3BeV/c K+d +Tr

3.0 3.0 (a). 2.8-111 2.8 • - 2.6 26 :\ \ * K • 24 . • 2.4

\\ 22 22/__ 15 (b)

2 .Q6 4 126 35 cli

25-

8 .0 .2 1.4 -0.6 -0.2 02 0.6 1.0 MK+,r _ (BeV) . Cos dK

r/ 2 [mb/(BeV) 2 ] 0 0.2 0.4 0.6 08 (c) 0.8 .K*O *0 - 0.6 Non K .6 K*O

: /0.4 1

02 ,-----02

0 C 0.6 1.0 1.4 LB 2.2 4 8 12 16 20 -. M 2 . - (BeV) 2 Number of events oer 0.04 (BeV) 2 lo - Miji -0 0

(8eV) 2 .

MUB-10194 -58- IJCRL-16744

three.-particle system. The Chew-Low plot boundary then forces these. events to occur at low mass values. This might be considered as a trivial explanation of the effect. A virtual pion may be scattered off the deuteron, leaving a 11± d structure whose mass corresponds roughly to formation by one of the nucleons in the deuteron of an N++(1238) or N'(1Z38) without deuteron breakup. In this case we are dealing with virtual pion exchange in accordance with the Drell process, which gives rise to a broad pTr± (or Kii) enhancement, On JI this interpretation the observed alignment of the p° (or K ) can be understood as well. Coherent production of a 1+ state would also lead to alignment of the p° (orK ° ), as discussed in the previous section. In this case the question arises why the A 1 [or K(1.3ZO)] if they are indeed 1+ mesons do not show up. One possibility here is that the coherent process actually enhances 49 a 1 nonresonant state! As has been reeinphasized recently, the coherent process will primarily excite states which can be produced with exchange of angular momentum only. Thus for a 0 incident particle and J= we get states with 0, i, 2,' '' formed, Of these the 0 state corre- sporids to "elastic" diffraction scattering, while the 1 state is the first more complex coherent state beyond diffraction scattering. If either (b) or (c) is the correct interpretation here it is very likely that this process also contributes to the "coherent" scattering observed in the heavy-liquid chamber. In fact the entire A 1 phenomenon observed in that experiment could be of this nature. An obvious test here would be to study the Tr and K+ interactions leading to three bosons in a heavy-liquid chamber as a function of incident momentum,

VIII. SUMMARY AND CONCLUSION

We summarize the tests discus sed here in Table II, There appears little doubt that in both cases discussed here the Deck mechanism plays an important role. The real question boils down to this: is there a re.sonance in addition to the kinematical enhancement effect? The principal evidence favoring this assumption is the extremely 7 sharp A 1 peak observed in the data of Deutschmann et al, on the 8-BeV/c -59- tJCRL-6744

.4-i 0 NI —4 a) U)a) 44 0 0 04 o U) a a) 0 0 '--4 -i -i 0a) -o 4J - U) 0 0 ...4U) .1 U) U) r. 4-4 NI I _i i—i OU) 0 4 a) z z U) 0 41 —I 0U) "-4 _i 0 .4-i NI . U)U) U) 0-i 1i * --4 a) cvj 0 a) I_-I 0 0.4 .01 04 0+ . 0 -.c: 0 Cd - 0 :t NI U 0 Cd 0;U) c-4 a) 0 00 a) 0 UD+ 0' 0 a) NI t cU) ri ...4 -'-4 IVI 0 —4 NI bID 0-i U)a) 04 cn I --4 (j -i 0-i 4a) 41 0 a) 4 ,I U P4 0 0 OQ-i o '-4 od •d ,40 U) < 41 '-CU) Cd a) 04 "-4 ;-4 .4-ia) 0(1) 0'.- ' U a) Ct 0C-4 Z NI 1 L 04 0. a) 0 Oa) r. r. 0 0 Cd U) 0 "-4 4 U) a) .4-i • (a) 43 a) U) d 0 -p C.-. Cl. a) -, ± 0 U) 0 H 0 -1 .4-i ¼) U) 0 0 i—i 0 4-4 -4 0 U) co Zcd :1 :1 U U 00

I::; it a) .4-11:1

0 410—in-- Cl. a) -1 -- U)

.4-i 4) NI c Cd 0 0 4-i a) U)U)

a)a) 0 -'--I 0 4-i 0 a) 0 04 r4 a) bID - -i-i .4-i.4- .1_i U) 0 00 a), * E. - ---r bAD - 4 -4 0 ;-4 * c c . 0 a)a) Cd o 0 E2E lU 0- E-.4H UCRL-16744

+H IT, p reaction and the similar sharp K (13Z0) peak observed by us in the 4,6-Be V/c K + p reaction, If these peaks persist with improved statistics (although it is not obvious at present that they will), it may become possible to perform the tests described here on a select sample of events from the narrow peaks. Thus we feel that considerably more data will be required before the presence of bona fide mesons can be either established or corn- pletely ruled out. We wish to acknowledge the.help and effort contributed by Dr. Benjamin C. Sheh to all phases of this work. We wish to thank Dr. Janos Kirz and Professor George H. Trilling for a number of discussions and helpful comments on this work. We also wish to acknowledge the help and hospitality offered to us by Professor Alladi Ramakrishnan and the other members of the Institute of Mathematical Science in Maidras, India, during our all-too-brief stay there. This work was done under auspices of the U. S. Atomic Energy Commission, and, for one of us (SG), of the John S. Guggenheim Foundation. -6t- LJCRL-16744

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