Fourth order correlation of baryon number and electric charge as a better magnetometer of QCD

This work focuses on the fourth order correlations ${\chi }_{31}^{BQ}$, ${\chi }_{31}^{QB}$, ${\chi }_{22}^{BQ}$, ${\chi }_{31}^{BS}$, ${\chi }_{31}^{SB}$, ${\chi }_{22}^{BS}$, ${\chi }_{31}^{QS}$, ${\chi }_{31}^{SQ}$, ${\chi }_{22}^{QS}$, ${\chi }_{211}^{BQS}$, ${\chi }_{211}^{QBS}$, ${\chi }_{211}^{SBQ}$ of baryon number $B$, electric charge $Q$ and strangeness $S$ at finite temperature, magnetic field and vanishing quark chemical potential. The study is carried out in the framework of a three-flavor PNJL model, considering both cases with and without inverse magnetic catalysis effect. We find that, fourth order correlations ${\chi }_{31}^{BQ}$ at chiral restoration phase transition is more sensitive to the magnetic field than other second order and fourth order correlations and fluctuations, and can be served as a more effective magnetometer of QCD.