QCD phase diagram at finite isospin and baryon chemical potentials with the self-consistent mean field approximation

Abstract

The self-consistent mean field approximation of two-flavor NJL model with introducing a free parameter $\alpha$ to reflect the competition between "direct" channel and the "exchange" channel, is employed to study QCD phase structure at finite isospin chemical potential ${\mu }_I$, finite baryon chemical potential ${\mu }_B$ and finite temperature $T$, especially the location of the QCD critical point. It is found that, for fixed isospin chemical potentials the lower temperature of phase transition is obtained with $\alpha$ increasing in the $T-{\mu }_I$ plane, and the largest difference of the phase transition temperature with different $\alpha$'s appears at ${\mu }_I\sim 1.5m_{\pi }$. At ${\mu }_I=0$ the temperature of the QCD critical end point (CEP) decreases with $\alpha$ increasing, while the critical baryon chemical potential increases. At high isospin chemical potential (${\mu }_I=500$ MeV), the temperature of the QCD tricritical point (TCP) increases with $\alpha$ increasing, and in the regions of low temperature the system will transit from pion superfluidity phase to the normal phase as ${\mu }_B$ increases. At low temperatures, the critical temperature of QCD phase transition with different $\alpha$'s rapidly increases with ${\mu }_I$ at the beginning, and then increases smoothly around ${\mu }_I>300$ MeV. In high baryon density region, the increase of the isospin chemical potential will raise the critical baryon chemical potential of phase transition.

Comments: 7 pages, 9 figures. arXiv admin note: substantial text overlap with arXiv:2003.02988