In-medium reduction of the η' mass √s_NN = 200 GeV Au+Au collisions

¹ MTA KFKI RMKI, H-1525 Budapest 114, P.O.Box 49, Hungary
² Dept. Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138, USA

^a e-mail: vertesi@rmki.kfki.hu

Abstract

A reduction of the mass of the η' (958) meson may indicate the 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 √s_NN = 200 GeV Au+Au collisions at RHIC. To describe this combined PHENIX and STAR dataset, an in-medium η' 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.