Chemical nonequilibrium and deconfinement in 200A GeV sulphur induced reactions

We interpret hadronic particle abundances produced in S-Au/W/Pb 200A GeV reactions in terms of the final state hadronic phase space model and determine by a data fit of the chemical hadron freeze-out parameters. Allowing for the flavor abundance nonequilibrium a highly significant fit to experimental particle abundance data emerges, which supports the possibility of strangeness distillation. We find under different strategies stable values for freeze-out temperature Tf=143±3 MeV, baryochemical potential μB=173±6 MeV, ratio of strangeness (γs) and light quark (γq) phase space occupancies γs/γq=0.60±0.02, and γq=1.22±0.05 without accounting for collective expansion (radial flow). When introducing flow effects which allow a consistent description of the transverse mass particle spectra, yielding n-tilde rvec vcn-tilde=0.49±0.01 c, we find γs/γq=0.69±0.03, γq=1.41±0.08. The strange quark fugacity is fitted at λs=1.00±0.02 suggesting chemical freeze-out directly from the deconfined phase. copyright 1999 The American Physical Society