Lévy-stable two-pion Bose-Einstein correlations in $\sqrt{s_{{}_{NN}}}=200$ GeV Au$+$Au collisions

Abstract

We present a detailed measurement of charged two-pion correlation functions in 0%-30% centrality $\sqrt{s_{{}_{NN}}}=200$ GeV Au$+$Au collisions by the PHENIX experiment at the Relativistic Heavy Ion Collider. The data are well described by Bose-Einstein correlation functions stemming from Lévy-stable source distributions. Using a fine transverse momentum binning, we extract the correlation strength parameter $\hat{I}»$, the Lévy index of stability $\hat{I}\pm$ and the Lévy length scale parameter $R$ as a function of average transverse mass of the pair $m_T$. We find that the positively and the negatively charged pion pairs yield consistent results, and their correlation functions are represented, within uncertainties, by the same Lévy-stable source functions. The $\hat{I}»(m_T)$ measurements indicate a decrease of the strength of the correlations at low $m_T$. The Lévy length scale parameter $R(m_T)$ decreases with increasing $m_T$, following a hydrodynamically predicted type of scaling behavior. The values of the Lévy index of stability $\hat{I}\pm$ are found to be significantly lower than the Gaussian case of $\hat{I}\pm =2$, but also significantly larger than the conjectured value that may characterize the critical point of a second-order quark-hadron phase transition.

448 authors, 25 pages, 11 figures, 4 tables, 2010 data. v3 is version accepted for publication in Phys. Rev. C with some Table II numbers and Fig. 5 updated to match publication. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.html