Mott dissociation and kaon to pion ratio in the EPNJL model

TL;DR

This paper investigates meson behavior and kaon to pion ratios in the SU(3)PNJL model at finite temperature and chemical potential, explaining the horn effect and mass splitting without linking it to a critical endpoint.

Contribution

It introduces a detailed analysis of kaon and pion ratios and mass splitting within the EPNJL model, clarifying the horn effect's origin and its independence from the QCD critical endpoint.

Findings

Mass splitting of kaons and anti-kaons arises from density effects.

The horn effect in K+/π+ ratio is due to nonequilibrium pion chemical potential.

K/π ratios show different behavior at low and high collision energies.

Abstract

The behaviour of pseudoscalar mesons within the SU(3)PNJL-like models is considered for finite T and $\mu_B$. We compare the pole approximation (Breit-Wigner) with the Beth-Uhlenbeck approach. We evaluate the $K/\pi$ ratios along the phase transition line in the T-$\mu_B$ plane with constant and $T/\mu_B$-dependent pion and strange quark chemical potentials. Using the model, we can show that the splitting of kaon and anti-kaon masses appears as a result of introduction of density and this explains the difference in the $K^+/\pi^+$ ratio and $K^-/\pi^-$ ratio at low $\sqrt{s_{NN}}$ and their tendency to the same value at high $\sqrt{s_{NN}}$. A sharp "horn" effect in the $K^+/\pi^+$ ratio is explained by the enhanced pion production which can be described by occurrence of a nonequilibrium pion chemical potential of the order of the pion mass. We elucidate that the horn effect is not related to the existence of a critical endpoint in the QCD phase diagram.