Centrality dependence of L\'evy-stable two-pion Bose-Einstein correlations in $\sqrt{s_{_{NN}}}=200$ GeV Au$+$Au collisions

• Main Authors: PHENIX Collaboration, Ajitanand, N. N, Al-Ta'ani, H, Angerami, A, Aramaki, Y, Barish, K. N, Bok, J. S, Chi, C. Y, Choi, S, Chvala, O, Cianciolo, V, Citron, Z, Cole, B. A, Csörgő, T, Datta, A, Dharmawardane, K. V, Dion, A, Drapier, O, Esha, R, Eyser, K. O, Finger, M, Fitzgerald, D, Fleuret, F, Fokin, S. L, Frantz, J. E, Gong, X, Goto, Y, Perdekamp, M. Grosse, Guo, T, Gustafsson, H. -Å, Hahn, K. I, Hollis, R. S, Hori, Y, Imrek, J, Isenhower, D, Jouan, D, Kamin, J, Kapustinsky, J, Kasai, M, Kim, B. I, Kim, Y. -J, Klatsky, J, Kline, P, Kotchetkov, D, Kovacs, L, Krizek, F, Kurosawa, M, Kwon, Y, Lee, K. S, Leitch, M. J, Lewis, B, Levy, L. A. Linden, Makek, M, McCumber, M, McGlinchey, D, Mendoza, M, Milov, A, Miyachi, Y, Miyasaka, S, Mohanty, A. K, Nagy, M. I, Nakamura, K. R, Nakamura, T, Nattrass, C, Nihashi, M, Novák, T, Nukazuka, G, Nyanin, A. S, Oskarsson, A, Ouchida, M, Pak, R, Park, B. H, Park, S, Petti, R, Purschke, M. L, Rak, J, Read, K. F, Sakaguchi, T, Shein, I, Sickles, A, Singh, B. K, Smith, K. L, Sondheim, W. E, Stankus, P. W, Sugitate, T, Sukhanov, A, Taneja, S, Taranenko, A, Tennant, E, Themann, H, Tomášek, L, Tsuji, T, Vale, C, Vargyas, M, Virius, M, Vértesi, R, Wei, F, Younus, I, You, Z, Yushmanov, I. E
• Format: Journal Article
• Language: English
• Published: 11.07.2024
• Subjects: Physics - Nuclear Experiment
• DOI: 10.48550/arxiv.2407.08586

The PHENIX experiment measured the centrality dependence of two-pion Bose-Einstein correlation functions 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 L\'evy-stable source distributions. The extracted source parameters are the correlation-strength parameter $\lambda$, the L\'evy index of stability $\alpha$, and the L\'evy-scale parameter $R$ as a function of transverse mass $m_T$ and centrality. The $\lambda(m_T)$ parameter is constant at larger values of $m_T$, but decreases as $m_T$ decreases. The L\'evy scale parameter $R(m_T)$ decreases with $m_T$ and exhibits proportionality to the length scale of the nuclear overlap region. The L\'evy exponent $\alpha(m_T)$ is independent of $m_T$ within uncertainties in each investigated centrality bin, but shows a clear centrality dependence. At all centralities, the L\'evy exponent $\alpha$ is significantly different from that of Gaussian ($\alpha=2$) or Cauchy ($\alpha=1$) source distributions. Comparisons to the predictions of Monte-Carlo simulations of resonance-decay chains show that in all but the most peripheral centrality class (50%-60%), the obtained results are inconsistent with the measurements, unless a significant reduction of the in-medium mass of the $\eta'$ meson is included. 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.