Speaker
Description
We study the effect of the QCD critical point on moments of fluctuations of experimental observables in theoretical model at energies similar to RHIC beam energy scan (BES) energies. In heavy-ion collision experiments, the QCD critical point can be found via the non-monotonic behavior of many fluctuation observables as a function of the collision energy. Locating the point requires a scan of the phase diagram by varying temperature and chemical potential which can be performed by varying the initial collision energy $\sqrt{s}$. The event-by-event particles multiplicity fluctuations can be characterized by the moments of the event-by-event multiplicity distributions. The most important characteristic feature of a critical point is increase and divergence of fluctuations. The magnitude of fluctuations in conserved quantities like net-baryon, net-charge and net-kaon at finite temperature are distinctly different in the hadronic and QGP phase. The ratios of the moments as experimental observables cancel the volume of the system and can be directly compared to the ratios of susceptibilities from theoretical calculation. Higher-order moments like mean (M), variance ($\sigma^2$), skewness (S), kurtosis ($\kappa$) depend on the higher power of $\xi$ i.e., $S\sim\xi^{4.5}$ and $\kappa\sim\xi^{7}$. Experimentally measuring conserved quantities is difficult due to experimental limitation, therefore net-proton, net-pion, net-kaon are measure as the proxy of ($\Delta B$, $\Delta Q$, $\Delta S$). Thus the need for different models becomes predominant to estimate the value of different observables. The Polyakov loop enhanced Nambu-Jona-Lasinio (PNJL) model of QCD, is such an effective model, which possesses the benefit of having characteristics similar to the observables. Higher-order moments like skewness (S), kurtosis ($\kappa$) and their products ($ s\sigma$, $\kappa\sigma^{2}$) which are calculated in the PNJL model, are sensitive to the correlation length of the hot and dense medium created in the collision, making them more prone to search for the critical point. We also compare the value of higher-order moment products or cumulant ratios with STAR and HRG data with different values to understand the existence of critical point.
| Session | Heavy Ions and QCD |
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