Indirect observation of an in-medium eta' mass reduction in sqrt(s_{NN})=200 GeV Au+Au collisions

TL;DR

This study analyzes pion correlation data from high-energy gold-gold collisions to infer a significant in-medium reduction of the eta' meson mass, suggesting possible U_A(1) symmetry restoration in hot, dense matter.

Contribution

It provides evidence for at least a 200 MeV eta' mass reduction in heavy-ion collisions, indicating symmetry restoration not previously confirmed.

Findings

At least 200 MeV eta' mass reduction needed

Supports U_A(1) symmetry restoration in hot dense matter

Implications for the nature of the QCD vacuum

Abstract

PHENIX and STAR data on the intercept parameter of the two-pion Bose-Einstein correlation functions in sqrt(s_{NN}) = 200 GeV Au+Au collisions are analyzed in terms of different models of hadronic multiplicities. 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 the considered model class. Such a significant eta' mass modification may indicate the restoration of the U_A(1) symmetry in a hot and dense hadronic matter and the return of the 9th "prodigal" Goldstone boson.