Phase diagrams in the hadron–Polyakov–Nambu–Jona-Lasinio model

Abstract

The two-Equation of State (Two-EoS) model is used to describe the hadron-quark phase transition in dense-hot matter formed in heavy-ion collisions. The non-linear Walecka model is used to describe the hadronic phase. For the quark phase, the Nambu--Jona-Lasinio model coupled to Polyakov-Loop fields (PNJL) is used to include both the chiral and (de)confinement dynamics. The phase diagrams are derived from the Gibbs conditions and compared with the results obtained in the Hadron-NJL model without confinement. As in the Hadron-NJL case a first order transition is observed, but with a Critical-End-Point at much higher temperature, consequence of the confinement mechanism that reduces the degrees of freedom of the quark matter in proximity of the phase transition. Particular attention is devoted to the phase transition in isospin asymmetric matter. Interesting isospin effects are found at high baryon density and reduced temperatures, in fact common also to other quark models, like MIT-Bag and NJL model. Some possible observation signals are suggested to probe in Heavy-Ion Collision (HIC) experiments at intermediate energies.