NUKLEONIKA 2004, 49(Supplement 2):s41-s44

PION ENTROPY AND PHASE SPACE DENSITY IN RHIC COLLISIONS

John G. Cramer for the STAR Collaboration

Center for Experimental Nuclear Physics and Astrophysics, Department of Physics, University of Washington, Seattle, WA 98195-1560, USA

We present the source-averaged phase space density f, the entropy per particle Sp/Np, and the total pion entropy per participant (dSp/dy)/Np extracted at midrapidity in six momentum intervals and seven centrality intervals, for pions produced in ÖsNN = 130 GeV Au+Au collisions at RHIC. These are inferred from measured p- momentum spectra and HBT correlation analysis of pion data from the STAR detector. The source-averaged pion phase space density f reaches a plateau with centrality and is significantly larger than that observed for ÖsNN = 17 GeV Pb+Pb central collisions at the CERN SPS. The entropy per particle Sp/Np is relatively low, approaching the Landau limit. The total pion entropy per participant (dSp/dy)/Np is about 6.5 ± 0.1, independent of centrality, suggesting that there is no per-participant increase in initial entropy production with increasing collision centrality.