Enhanced strange particle production, nonstatistical multiplicity fluctuations and two-pion Bose-Einstein correlations were measured in O, S-nucleus reactions at 60 and 200 GeV/nucleon. The results indicate significant collective effects in high-energy nucleus-nucleus collisions.
CENTRAL COLLISIONS.
CENTRAL COLLISIONS.
Particle correlations of the central collision events of 32 S + Pb at 200 GeV/AMU have been studied by utilizing a Magnetic-Interferometric-Emulsion-Chamber (MAGIC) detector. Particle angles, momentum, and charge-signs are measured for all produced charged tracks for each event. Two-particle correlation functions, C 2 = dN (¦ p 1 − p 2 ¦= q )/ dp 1 dp 2 , for (++), (−−) and (+-) particles are examined. A source radius around 4 – 6 fm is observed for overall identical particle correlations, while unexpected short-range correlations of unlike-sign pairs are observed in the high rapidity region. An analysis of unlike-sign pairs in terms of resonance decays indicated that a large amount (40% relative to pions) of η or ω mesons (decaying into 3 π), or of scalar iso-scalar σ mesons (decaying into 2π) would be required to explain some of the data. Multi-particle charge-sign clusters are recognized; however, their “run-test” and “conjugate-test” show small deviations from statistical fluctuations.
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