Fluctuations and correlations of hot QCD matter in an external magnetic field

TL;DR

This study investigates how external magnetic fields influence fluctuations and correlations of conserved charges in hot QCD matter, revealing enhanced fluctuations and potential probes for early-stage magnetic fields in heavy-ion collisions.

Contribution

It provides the first detailed analysis of magnetic field effects on conserved charge fluctuations using the 2+1 flavor Polyakov--Nambu--Jona-Lasinio model, highlighting sensitive observables.

Findings

Magnetic field increases fluctuations and correlations in the chiral crossover regime.

Quadratic fluctuations transition more abruptly under magnetic influence.

Certain ratios of fluctuations are highly sensitive to magnetic fields and can serve as probes.

Abstract

Effects of an external magnetic field on the fluctuations of quark number, fluctuations and correlations of conserved charges, including baryon number, electric charge and strangeness, are studied in the 2+1 flavor Polyakov--Nambu--Jona-Lasinio model. We find that magnetic field increases fluctuations and correlations in the regime of chiral crossover. It makes the transition of quadratic fluctuations more abrupt, and the peak structure of quartic fluctuations more pronounced. Our calculations indicate that $\chi_{4}^{B}/\chi_{2}^{B}$, $\chi_{4}^{Q}/\chi_{2}^{Q}$, and $\chi_{11}^{BQ}$ are very sensitive to the external magnetic field and maybe can be used for probes for the strong magnetic field produced in the early stage of noncentral collisions.