Are there universal freeze-out parameters for central 158AGeV Pb+Pb collisions?

Abstract

Earlier attempts to extract parameters of kinetic freeze-out in Pb+Pb collisions at 158$A$GeV are critically reviewed. Many of these analyses have used approximations which have significant impact on the extracted parameters. Simple estimates are obtained which attempt to avoid the most critical approximations. It is pointed out that constraints based on pion interferometry are less reliable than those from momentum spectra. A universal set of freeze-out parameters from transverse mass spectra would require T > 135 MeV and <beta> < 0.35.