Observation of PartialUA(1)Restoration from Two-Pion Bose-Einstein Correlations

Abstract

The effective intercept parameter of the two-pion Bose-Einstein correlation function, ${\ensuremath{\lambda}}_{*}$, is found to be sensitive to the partial restoration of ${\mathrm{U}}_{A}(1)$ symmetry in ultra-relativistic nuclear collisions. An increase in the yield of the ${\ensuremath{\eta}}^{\ensuremath{'}}$ meson, proposed earlier as a signal of partial ${\mathrm{U}}_{A}(1)$ restoration, is shown to create a ``hole'' in the low ${p}_{t}$ region of ${\ensuremath{\lambda}}_{*}$. A comparison with NA44 data and central $\mathrm{S}+\mathrm{Pb}$ collisions at $200A\mathrm{GeV}$ is made, and implications for future heavy ion experiments are discussed.