  A reduction of the mass of the \eta'(958) meson may indicate the restoration
of the UA(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 multiplicities. Energy,
system size and centrality dependence of the observed effect is also discussed.
