Negative strange quark chemical potential. A concise, well defined indication of the quark-deconfinement phase transition

Abstract

We have studied the variation of a thermodynamic quantity, the strange chemical potential, in the phase diagram of nuclear matter, by employing the partition function in each domain and enforcing strangeness conservation. We propose that the change in the sign of the strange quark chemical potential, from positive in the hadronic phase to negative in the deconfined quark-gluon phase, to be a new, unique, concise and well-defined indication of the quark-deconfinement phase transition in nuclear matter. This signature is independent of model parameters and interaction mechanisms. We propose also that, for a state in the deconfined region following an isentropic path to hadronization via a second order phase trasition, the fugacities of the equilibrated quark flavours, once fixed in the primordial state, remain constant throughout the hadronization process. This would enable the knowledge of the thermodynamic quantities of states situated beyond the hadronic phase. Data from nucleu-nucleus interactions at AGS and SPS give support to our proposals.