Speaker
Описание
Due to the recent STAR data on the polarization of the $\Lambda$ hyperons produced in heavy ion collisions, it is interesting to consider the QCD phase transition in a medium exhibiting persistent polarization. Since during the chiral phase transition, the quarks acquire dynamical mass and the conservation of the axial charge current $J^\mu_A$ is broken, the chiral chemical potential $\mu_A$ is not suitable to thermodynamically account for the fermion polarization. Noting that the helicity current $J^\mu_H$ remains conserved even at finite fermion mass, we propose to model the fermion polarization via the helicity chemical potential $\mu_H$. In the framework of the linear $\sigma$ model with quarks, LSM$_q$, we show that the vector and helical chemical potentials $\mu_V$ and $\mu_H$ form a dual pair, due to the symmetry of the free energy $\Omega(\mu_V,\mu_H)=\Omega(\mu_H,\mu_V)$. In this talk, we discuss on the impact of a finite $\mu_H$ on the phase diagram associated with the chiral phase transition with a particular focus on the new critical points that emerge at sizable $\mu_H$.
