Magnetic Field Effects on Hadron Yields and Fluctuations

We explore the impact of an external magnetic field on hadron yields and fluctuations in a thermalized system within the hadron resonance gas (HRG) model using an expanded Thermal-FIST package. The magnetic field sizably enhances the final proton-to-pion (p/$\pi$) ratio due to $\Delta(1232)^{++}$ decay feeddown indicating that this ratio may serve as a potential magnetometer for freeze-out conditions. At the same time, magnetic field does not generate additional dynamical fluctuations of hadron numbers. This suggests that fluctuations in heavy-ion collisions provide limited additional information about the magnetic field beyond what is already inferred from mean multiplicities.