Restriction on the form of the quark anomalous magnetic moment from lattice QCD results*

Abstract

Abstract The quark anomalous magnetic moment (AMM) is dynamically generated through spontaneous chiral symmetry breaking. It has been revealed that, even though its exact form is still unknown, the quark AMM is essential to exploring quark matter properties and QCD phase structure under external magnetic fields. In this study, we take three different forms of the quark AMM and investigate its influence on the chiral phase transition under a magnetic field. In general, a negative (positive) quark AMM acts as a magnetic-catalyzer (magnetic-inhibitor) for chiral symmetry breaking. It is found that a constant quark AMM drives an unexpected 1st order chiral phase transition, a quark AMM proportional to the chiral condensate flips the sign on the chiral condensate, and a quark AMM proportional to the square of the chiral condensate suppresses the magnetic enhancement in the chiral condensate at finite temperatures while retaining the chiral crossover phase transition. We also evaluate the intrinsic temperature dependence of the effective AMM form by fitting the effective model result of the chiral condensate to lattice QCD data, which may have a nontrivial correlation with the chiral phase transition.