A reduction of the mass of the eta'(958) meson may signal restoration of the
U_A(1) symmetry in a hot and dense hadronic matter, corresponding to the return
of the 9th, "prodigal" Goldstone boson. We report on an analysis of a combined
PHENIX and STAR data set on the intercept parameter of the two-pion
Bose-Einstein correlation functions, as measuremed in sqrt(s(NN)) = 200 GeV Au
+ Au collisions at RHIC. To describe this combined PHENIX and STAR dataset, an
in-medium eta' mass reduction of at least 200 MeV is needed, at the 99.9 %
confidence level in a broad model class of resonance abundances.Comment: 12 pages, 5 figures, to appear in the Proceedings of the Gribov'80
Memorial Worksho