Correlations of conserved-number mixed susceptibilities in a hadron resonance gas model

Abstract

The ratios of off-diagonal and diagonal susceptibilities of conserved charges are studied using a hadron resonance gas (HRG) model with an emphasis towards providing a proper baseline for comparison to the corresponding future experimental measurements. We have studied the effect of kinematic acceptances, transverse momentum (${p}_{T}$), and pseudorapidity ($\ensuremath{\eta}$), and different charged states on the ratios of the calculated susceptibilities. We find that the effect of ${p}_{T}$ and $\ensuremath{\eta}$ acceptance on the ratio of the susceptibilities is small relative to their dependence on the beam energy or the charged states of the used particles. We also present a HRG based calculation for various combinations of cumulant ratios of protons and pions, recently proposed as robust observables (with no theoretical uncertainties) for critical point search in the experiments. These results which increase as a function of collision energy will provide a better baseline for noncritical point physics compared to Poisson expectation.