The VII-th International Conference on the Initial Stages of High-Energy Nuclear Collisions : Initial Stages 2023

Centrality dependence of Lévy-stable two-pion Bose-Einstein correlations in $\sqrt{s_{NN}}= 200$ GeV Au+Au collisions measured by PHENIX at RHIC

Not scheduled

2h

Københavns Universitetsbibliotek Nord

Poster Collective dynamics from small to large systems Reception and poster session

Speaker

Sandor Lokos (Institute of Nuclear Physics Polish Academy of Sciences (PL))

Description

The centrality dependence of two-pion Bose-Einstein correlation functions is measured by the PHENIX experiment in $\sqrt{s_{NN}} = 200$ GeV Au+Au collisions at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. The data are well represented by Lévy-stable source distribution. We extracted the correlation strength parameter $\lambda$, the Lévy index of stability $\alpha$ and the Lévy scale parameter $R$ as a function of transverse mass and centrality. We observe that $\lambda(m_T)$ is constant at larger values of $m_T$ but decreases as $m_T$ decreases. The Lévy scale parameter $R(m_T)$ decreases with $m_T$ and exhibits a clear centrality ordering. The Lévy exponent $\alpha(m_T)$ is independent of $m_T$ within uncertainties in each investigated centrality bin, but it shows a clear centrality dependence. At all centralities, the Lévy exponent $\alpha$ is significantly different from that of Gaussian ($\alpha=2$) or Cauchy ($\alpha=1$) source distributions. The data are compared to Monte Carlo simulations of resonance decay chains. In all but the most peripheral centrality class (50--60\%) they are found to be inconsistent with the measurements unless a significant reduction of the in-medium mass of the $\eta^\prime$ meson is included. In each centrality class, the best value of the in-medium $\eta^\prime$ mass is compared to the mass of the $\eta$ meson as well as to several theoretical predictions that consider restoration of $U_A(1)$ symmetry in hot hadronic matter.