Effect of resonance decay on conserved number fluctuations in a hadron resonance gas model

We study the effect of charged secondaries coming from resonance decay on the net-baryon, net-charge, and net-strangeness fluctuations in high-energy heavy-ion collisions within the hadron resonance gas (HRG) model. We emphasize the importance of including weak decays along with other resonance decays in the HRG, while comparing with the experimental observables. The effect of kinematic cuts on resonances and primordial particles on the conserved number fluctuations are also studied. The HRG model calculations with the inclusion of resonance decays and kinematical cuts are compared with the recent experimental data from STAR and PHENIX experiments. We find good agreement between our model calculations and the experimental measurements for both net-proton and net-charge distributions.

Figure 1

Collision energy dependence of susceptibility ratios (${\chi }^{\left(2\right)}/{\chi }^{\left(1\right)},{\chi }^{\left(3\right)}/{\chi }^{\left(2\right)},{\chi }^{\left(4\right)}/{\chi }^{\left(2\right)}$, and ${\chi }^{\left(3\right)}/{\chi }^{\left(1\right)}$) calculated in full phase space for net baryons without resonance decay, primordial protons, and primordial protons with resonance decay including weak-decay resonances.

Figure 2

Collision energy dependence of susceptibility ratios (${\chi }^{\left(2\right)}/{\chi }^{\left(1\right)},{\chi }^{\left(3\right)}/{\chi }^{\left(2\right)},{\chi }^{\left(4\right)}/{\chi }^{\left(2\right)}$, and ${\chi }^{\left(3\right)}/{\chi }^{\left(1\right)}$) calculated in full phase space for net charge without resonance decay, primordial charged particles $\left(\pi ,K,p\right)$, and primordial charged hadrons with resonance decay including weak-decay resonances.

Figure 3

Collision energy dependence of susceptibility ratios (${\chi }^{\left(2\right)}/{\chi }^{\left(1\right)},{\chi }^{\left(3\right)}/{\chi }^{\left(2\right)},{\chi }^{\left(4\right)}/{\chi }^{\left(2\right)}$ and ${\chi }^{\left(3\right)}/{\chi }^{\left(1\right)}$) calculated in full phase space for net strangeness without resonance decay, primordial kaons, and primordial kaons with resonance decay including weak-decay resonances.

Figure 4

Variation of susceptibility ratios (${\chi }^{\left(2\right)}/{\chi }^{\left(1\right)},{\chi }^{\left(3\right)}/{\chi }^{\left(2\right)},{\chi }^{\left(4\right)}/{\chi }^{\left(2\right)}$, and ${\chi }^{\left(3\right)}/{\chi }^{\left(1\right)}$) as a function of $\sqrt{s_{{}_{NN}}}$ calculated in full phase space for net-baryon without resonance decay, and primordial proton, primordial proton with and without including weak decay in addition to the strongly decaying resonances.

Figure 5

Variation of susceptibility ratios (${\chi }^{\left(2\right)}/{\chi }^{\left(1\right)},{\chi }^{\left(3\right)}/{\chi }^{\left(2\right)},{\chi }^{\left(4\right)}/{\chi }^{\left(2\right)}$, and ${\chi }^{\left(3\right)}/{\chi }^{\left(1\right)}$) as a function of $\sqrt{s_{{}_{NN}}}$ calculated in full phase space for net charge without resonance decay, primordial charged particles $\left(\pi ,K,p\right)$, and primordial charged particles with and without including weak decay in addition to the strongly decaying resonances.

Figure 6

Variation of susceptibility ratios (${\chi }^{\left(2\right)}/{\chi }^{\left(1\right)},{\chi }^{\left(3\right)}/{\chi }^{\left(2\right)},{\chi }^{\left(4\right)}/{\chi }^{\left(2\right)}$, and ${\chi }^{\left(3\right)}/{\chi }^{\left(1\right)}$) as a function of $\sqrt{s_{{}_{NN}}}$ calculated in full phase space for net strange without resonance decay, primordial kaons, and primordial kaons with and without including weak decay in addition to the strongly decaying resonances.

Figure 7

Collision-energy dependence of susceptibility ratios (${\chi }^{\left(2\right)}/{\chi }^{\left(1\right)},{\chi }^{\left(3\right)}/{\chi }^{\left(2\right)},{\chi }^{\left(4\right)}/{\chi }^{\left(2\right)}$, and ${\chi }^{\left(3\right)}/{\chi }^{\left(1\right)}$) for net protons for different $p_T$ acceptances within $\left|\eta \right|<0.5$. The results are for primordial protons with resonance decay including weak-decay resonances.

Figure 8

Collision-energy dependence of susceptibility ratios (${\chi }^{\left(2\right)}/{\chi }^{\left(1\right)},{\chi }^{\left(3\right)}/{\chi }^{\left(2\right)},{\chi }^{\left(4\right)}/{\chi }^{\left(2\right)}$, and ${\chi }^{\left(3\right)}/{\chi }^{\left(1\right)}$) for net charge for different $p_T$ acceptances with $\left|\eta \right|<0.5$. The results are for primordial charged particles $\left(\pi ,K,p\right)$ with resonance decay including weak-decay resonances.

Figure 9

Collision-energy dependence of susceptibility ratios (${\chi }^{\left(2\right)}/{\chi }^{\left(1\right)},{\chi }^{\left(3\right)}/{\chi }^{\left(2\right)},{\chi }^{\left(4\right)}/{\chi }^{\left(2\right)}$, and ${\chi }^{\left(3\right)}/{\chi }^{\left(1\right)}$) for net kaons for different $p_T$ acceptances within $\left|\eta \right|<0.5$. The results are for primordial kaons with resonance decay including weak-decay resonances.

Figure 10

The collision energy dependence of ${\sigma }^2/M,S\sigma$, and $\kappa {\sigma }^2$ of the net baryon calculated using HRG model including resonance decay contributions. The model calculations are compared with the experimental net proton cumulant ratios for the most-central (0%–5%) $\text{Au}+\text{Au}$ collisions by the STAR experiment.

Figure 11

The collision energy dependence of ${\sigma }^2/M,S\sigma$, and $\kappa {\sigma }^2$ of the net-charge calculated by using HRG model including resonance-decay contributions. The model calculations are compared with the experimental net-charge cumulant ratios for the most-central (0%–5%) $\text{Au}+\text{Au}$ collisions by the STAR experiment.

Figure 12

The collision energy dependence of ${\sigma }^2/M,S\sigma$, and $\kappa {\sigma }^2$ of the net charge calculated by using HRG model including resonance decay contributions. The model calculations are compared with the experimental net-charge cumulant ratios for the most-central (0%–5%) $\text{Au}+\text{Au}$ collisions by the PHENIX experiment.