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

The effective intercept parameter of the two-pion Bose-Einstein correlation function, lambda_*, is found to be sensitive to the partial restoration of U_A(1) symmetry in ultra-relativistic nuclear collisions. An increase in the yield of the eta' meson, proposed earlier as a signal of partial U_A(1) restoration, is shown to create a ``hole'' in the low p_t region of lambda_*. A comparison with NA44 data from central S+Pb collisions at 200 AGeV is made and implications for future heavy ion experiments are discussed.