Thermodynamically Anomalous Regions As A Mixed Phase Signal

TL;DR

This paper identifies thermodynamic irregularities at chemical freeze-out in heavy-ion collisions, suggesting these as signals of the mixed phase boundary to quark-gluon plasma, based on advanced hadron resonance gas modeling.

Contribution

It introduces a new signal for quark-gluon plasma formation based on thermodynamic anomalies observed at chemical freeze-out.

Findings

Abrupt change in effective degrees of freedom

Plateaus in entropy and pion number per baryon

Evidence for thermodynamic anomalous properties of the mixed phase

Abstract

Using the most advanced model of the hadron resonance gas we reveal, at chemical freeze-out, remarkable irregularities such as an abrupt change of the effective number of degrees of freedom and plateaus in the collision-energy dependence of the entropy per baryon, total pion number per baryon, and thermal pion number per baryon at laboratory energies 6.9-11.6 AGeV. On the basis of the generalized shock adiabat model we show that these plateaus give evidence for the thermodynamic anomalous properties of the mixed phase at its boundary to the quark-gluon plasma (QGP). A new signal for QGP formation is suggested and justified.