2308 E . L . L O M O N A N D M . H . P A R T O V I

*Work supported in part through funds provided by the Atomic Energy Commission under Contract NO, AT(11-1) -3069.

' Permanent address: Arya-Mehr liniversity of Technol- ogy, Teheran, Iran.

'w. T. Nut t and L. Wilets, preceding paper, Phys. Rev. D 3, 2303 (1973).

"M. H. Partcsvl and E. L. Lomon, Phys. Rev. D 2, 1999

(1970). he very brief discussion of PL in Sec. IV of Ref. 1 gives the inlpressioil that the PL approximations a r e arbitrary. The reader i s referred to Sees. IVA and IV B of Ref. 2 for a derivatio~l of every aspect of PL. A furtiler analysis of one of the approximations i s given in Ref. 13 of i-. l'zrtovi and E. Lomon, Phys. Rev. D 3, 1192 (i972).

P H Y S I C A I , R E V I E W D V O L U M E 8 , N U N I R E K 7 1 O C T O B E R 1 9 7 3

Influence of Peripheral Resonance Production on Angular Correlations Between Pions

J. Schlesinger Fuculte' des Sciences, Universife' de /'Elat, 7000 Mons, Belgium

(Received 13 April. 1973)

Following the results of Jain et a/. in K i p interactions at 12.7 GeV/c, we point out that a way to suppress the influence of peripheral resonances on angular corielations between piorrs is to irivestigate the P,-plane correlations. Results from p p interactions at 6.94 GeV/c are give^ a:. an example.

In a recent publication, Ja in el a1 .' reached the conclusion that angular correlat ions between pions [ GGLP (Goldhaber, Goldhaber, Lee, and p a i s ) effect] in the reaction IC'P- ~ ' p 2 n ' 2a- a t 12.7 GeV/c a r e mainly due t o the presence of the pe- r ipheral ly produced K*' and A" resonances. How- ever , a different explanation h a s been proposed by E s k r e y s et a2.' for the s a m e reaction a t 8.25 GeV/c. In th i s case , the GGLP effect would be caused by the difference between the two-particle m a s s distributions for like and unlike pions. A s the two explanations could be related by the kine- matic reflection of resonance production on the two-particle m a s s distributions, i t is felt that fur ther t es t s along this line should be performed, Such a tes t will be described below.

Since the production of K*' and A'' in K + P .- ~ " p 2 n + 2 n - a t 8.25 ~ e ~ / c h a s been found t o be 0 .441 0.03 and 0.24h 0.04, respectively, we feel that the removal of those resonances from the reaction constitutes a somewhat d ras t ic procedure

The uncertainty due to the a rb i t ra r iness of m a s s cu t s and to the conibinatorial background should a l s o be taken into account.

A method which h a s been t r ied in the analysis of the react ions 5)- PD2a '27- and $$- 3p2nt2 n-no a t 6.94 GeV/c3 could provide a n interesting al ter- native. In o rder to minimize the influence of resonance production, angular correlat ions should be studicd in a plane perpendicular to the line of flight of the resonance. Since the resonances here considered (in th i s case, A + + and & - - ) a r e produced peripherally, a good colnpromise is to use the P, ( t ransverse momenta) plane. The values of the y p a r a m e t e r s obtained for the pions a r e given in Table I. The values given by simple phase space a r e a l so indicated. The parameter T/ gives a measure of the over-all deviation of ~"~"nd from phase space:

, hke phase space unlike phase space 17' i Y - - Y 11-IY -Y I (1)

TABLE I. Angular-correlation parameters for the transverse momenta of outgoing pions for the reactionsFp-Fp2ai2a- and@ -pp2at2n-aO at 6.94 GeV/c.

-- -- (1) y ( a * ~ ' ) (2) y (st~-) (3) y(ataO) (2) + (3) y (phase space) 17

I N F L U E N C E O F P E R I P H E R A L R E S O N A N C E P R O D U C T I O N ON . . . 8 2309

By comparing the results given in Table I with while to extend this kind of analysis to other inter- those obtained by a standard analysis, one sees actions such a s K t # . that the effect remains of the same order of mag- nitude. We therefore feel that i t would be worth- I thank Dr . J . Skura for helpful discussions.

'P. L. Jain, W. M. Labuda, Z. Ahmad, and G. Pappas, Z. Sckera, Nucl. Phys, E, 44 (1972). Phys. Rev. D 1, 605 (1973). 3 ~ . Schlesinger, Ph.D. thes i s , Tel-Aviv University,

'E. Eskreys , J. Figiel, P. Malecki, K. Zalewski, Tel-Aviv, I s rae l , 1972 (unpublished). K. Eskreys , E. De Wolf, F. Grard , F. Verbeurc, 4 ~ . Alexander, I. Bar-Nir, S. Dagan, J. Grunhaus, D. Dri jard, W. Dunwoodie, A. Grant , Y. Goldschrnidt- P. Katz , Y. Oren, and J. Schlesinger, Nucl. Phys. Clermont, V. P. Henri , F. Muller, S. 0. Nielsen, and B35, 45 (1971).

P H Y S I C A L R E V I E W D V O L U M E 8 , N U M B E R 7 1 O C T O B E R 1 9 7 3

Effect of Resonance Production on Angular Correlation Between Pions

P. L. Jain, Z. Ahmad, G. Pappas, and W. M. Labuda High Energy Experimental Laboratory, Department of Physics, State University of New York at Buffalo, Buffalo, New York 14214

(Received 1 1 June 1973)

We have studied, in the P, plane, the angular correlations between pions produced in the six-prong interactions of K f p at 12.7 GeV/c in order to suppress the influence of peripherally produced resonances These results are compared with the values previously determined using space angles.

In a low-energy 5~ annihilation experiment, Goldhaber e t al.' discovered that the distribution of the c .m. angle between two pions depends on the charges of the pions. The average angle between pions of equal charges (?r 'ir*) was smaller than in the case of pa i rs of opposite charge (8' a-) (this i s known a s the GGLP effect). As a measure of the effect the parameter y was introduced, where

number of pa i rs with 8,,>90° Y= number of pa i rs with 8,,<90°

such that yt - > y * *. Bose-Einstein stat is t ics were invoked to explain these results , but were found to be inadequate. The GGLP effect has been studied in many experiments2 and i s found to be dependent on the leading particle; for example, (i) yt' > y-- for pr imary at and (ii) y--> y t t for pr imary am. To avoid the leading-particle effect, we recently3 studied the interaction K'P- ~ ~ p 2 a + 2 a - a t 12.7 GeV/c. We found that the abundant production of two resonances, N*++ and K*', influences consid- erably the distribution of the angles between the pions momenta. In Tables I and I1 a r e shown the revised values of the y parameter and the asym- metry parameter A defined by A = (y-1) / (y+ 1) for

different pa i rs of particles in the reaction Kt$-Kt#2rt2a-. We find that the y values for exotic combinations of (a'a') and (K+T+) were larger than for nonexotic pa i rs (a's-) and (K + a-), respectively. For the K f p interaction a t 8.25 GeV/c, Eskreys et a1 .4 have recently concluded that the GGLP effect could be a reflection of the differences in two-particle effective-mass distri- butions, which a r e different for like and unlike pairs . We know that the differences in the m a s s distributions for different pa i rs of pions a r e also observed when resonances a r e produced, which we have already discussed in our previous paper .3

We do agree with Eskreys e t a1 . that the GGLP effect is due to the difference between the m a s s distributions for like and unlike pa i rs . However, we believe that the difference in the mass distri- butions is a result of the resonant effects. We have demonstrated3 that the presence of resonances plays an important part in determing the GGLP effect.

Recently Schlesinger5 has pointed out that in order to minimize the influence of the resonances N* + + and K*O, which a r e produced peripherally, the angular distribution should be studied in the