Spin Polarization and Anomalous Magnetic Moment in a (2 + 1)-flavor Nambu-Jona-Lasinio model in a thermomagnetic background

TL;DR

This paper studies how tensor spin polarization and anomalous magnetic moments affect the phase transitions of magnetized quark matter in a (2+1)-flavor NJL model, revealing distinct impacts on magnetic catalysis and phase transition order.

Contribution

It introduces the effects of tensor spin polarization and anomalous magnetic moments into the NJL model, analyzing their influence on the QCD phase diagram under magnetic fields.

Findings

TSP enhances magnetic catalysis for light quarks.

AMM induces inverse magnetic catalysis and changes phase transition order.

Strange quark phase diagram remains crossover despite TSP or AMM.

Abstract

We investigate the magnetized QCD matter and chiral phase transition in a (2 {\th} 1)-flavor Nambu-Jona-Lasinio (NJL) model at finite temperature and chemical potential by comparing the contributions from the tensor spin polarization (TSP) and anomalous magnetic moment (AMM) of quarks. For light u and d quarks, when TSP and AMM are not considered, the magnetized system is characterized by magnetic catalysis. The introduction of TSP will further enhance the magnetic catalytic characteristics. On the other hand, when AMM is introduced, the phase-transition temperature decreases with the magnetic field, which is the feature of inverse magnetic catalysis. The phase diagram of u and d quarks will change from the crossover phase transition to the first order phase transition with the increase of magnetic field and chemical potential when AMM is induced. The phase diagram will not change from the crossover phase transition to the first-order phase transition when TSP is induced. For the phase diagram of strange s quark, whether TSP or AMM is induced, the phase diagram will keep a crossover phase transition with the increase of magnetic field and chemical potential.