Abstract:
Production of the K∗(892)0 and K∗(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 K∗ by about a factor of two in nucleus-nucleus reactions. The total yield ratios <K∗>/<K+> and <K∗>/<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.
