Speaker
Description
PHENIX has measured the centrality dependence of two-pion Bose-Einstein correlation functions in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. The data are well represented by L\'{e}vy-stable source distributions. Three source parameters have been extracted as a function of transverse mass $m_T$ and centrality: the correlation-strength parameter $\lambda$, the L\'{e}vy index of stability $\alpha$, and the L\'{e}vy-scale parameter $R$. At all centralities, the L\'{e}vy exponent $\alpha$ is significantly different from that of Gaussian ($\alpha=2$) or Cauchy ($\alpha=1$) source distributions. Monte-Carlo simulations of resonance-decay chains show that in all but the most peripheral centrality class (50\%-60\%), a significant reduction of the in-medium mass of the $\eta'$ meson is needed to match the data. In each centrality class, the best value of the in-medium $\eta'$ 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.
| Category | Experiment |
|---|---|
| Collaboration (if applicable) | PHENIX |
