Correlations in strange-particle pairs produced by π of 6, 11 and 18 GeV/c

Summary  Interactions of π− of 6.1, 11.6 and 18.1 GeV/c from the CERN PS on protons or quasi-free neutrons have been studied in the Ecole Polytechnique one-meter bubble chamber filled with a mixture 86% propane C3H8-14% freon CF3Br (by volume). Interactions have been selected in which two neutral strange particles are visible in order to study correlations among the strange particles and to study separately the behaviour of the K 1 0 ’s from the reactions: π−+N → K0 + -K0+nπ +N, π−+N → K0+Λ(Σ0)+nπ. It is found that πp c.m.s longitudinal and transverse momentum distributions are similar for the K 1 0 ’s from K0-K0 and from K0Y0 pairs. They tend to go forward in the c.m.s., small momenta being most probable. The baryon (A or nucleon) tends to go backward in the c.m.s. but with longitudinal momentum distributed roughly uniformly from slightly forward to the maximum kinematically possible backward. The K 1 0 ’s of K 1 0 K 1 0 pairs tend to have relative energy which is only a small fraction of that available with a distribution roughly independent of the π− beam momentum and of the πp c.m.s. momentum of the K 1 0 K 1 0 system. This effect does not seem to be due to phase-space limitations arising from backward peaking of the nucleon. We have too few events to decide whether this low-energy peaking of theQ-values is due to a resonance near 1.1 GeV or to a strong low-energy K0-K0 inter-action. Clear evidence of K* (0.89 GeV) and to a lesser degree of Y1* (1.39 GeV) are seen in K0A production. (47±15)% of all K 1 0 π+ systems are (K*)+, (30±20)% of all Λπ systems are Y1*. No evidence is seen of K* production in K 1 0 K 1 0 producing jets.