Variation of the strange-quark chemical potential in the phase diagram of nuclear matter

On the basis of lattice calculations, we require the existence of a deconfined quark matter region (0<a/sub s/<1) beyond the hadron gas phase, which goes asymptotically into the ideal quark-gluon plasma domain, in the phase diagram of nuclear matter. We consider empirically the dynamics of this region in terms of the order parameters and mass-scaled partition functions and derive an EoS. Then, the strange-quark chemical potential is expressed in a functional form of the temperature and light-quark chemical potential and its variation throughout the 3-region phase diagram is studied. We propose the change of the sign of the strange-quark chemical potential, from positive in the hadronic region to negative beyond, to be a unique, concise and well-defined indication of the quark- deconfinement phase transition in nuclear matter. Analysis of the nucleus-nucleus collision data from AGS and SPS is presented giving strong support to our proposal. (23 refs).