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K*(892)0 and K̅ *(892)0 production in central Pb + Pb, Si + Si, C + C, and inelastic p + p collisions at 158A GeV

Production of the K*(892)0 and K̅*(892)0 resonances was studied via their K+π− and K−π+ decay modes in central Pb+Pb, Si+Si, C+C, and inelastic p+p collisions at 158A GeV(√sNN=17.3 GeV) with the NA49 detector at the CERN SPS. Transverse momentum and rapidity distributions were measured and total yields were estimated. The yield of K* exceeds that of K̅* by about a factor of two in nucleus-nucleus reactions. The total yield ratios 〈K*〉/〈K+〉 and 〈K̅*〉/〈K−〉 are strongly suppressed in central Pb+Pb compared to p+p, C+C, and Si+Si collisions, in agreement with the expected attenuation of these short-lived resonance states in the hadronic phase of the expanding fireball. The UrQMD model, although incorporating such a scenario, does not provide a quantitative description of the experimental results. The statistical hadron gas model assuming the same freeze-out parameters for stable hadrons and resonances overestimates the 〈K*〉/〈K〉 ratios in central Pb+Pb collisions by about a factor of 2.5.

NA49; CERN; SPS; K(892); production

NA49 Collaboration