The variation of average transverse mass of identified hadrons with charge multiplicity has been studied for AGS, SPS, and RHIC energies. The observation of a plateau in the average transverse mass for multiplicities corresponding to SPS energies is attributed to the formation of a coexistence phase of quark gluon plasma and hadrons. A subsequent rise for RHIC energies may indicate a deconfined phase in the initial state. Several possibilities which can affect the average transverse mass are discussed. Constraints on the initial temperature and thermalization time have been put from the various experimental data available at SPS energies.

• Received 21 April 2003

DOI:https://doi.org/10.1103/PhysRevC.68.021901