The Return of The Prodigal Goldstone Boson

Abstract

We propose that the mass of the ${\eta }^{\prime }$ meson is a particularly sensitive probe of the properties of finite energy density hadronic matter and quark gluon plasma. We argue that the mass of the ${\eta }^{\prime }$ excitation in hot and dense matter should be small, and therefore that the ${\eta }^{\prime }$ production cross section should be much increased relative to that for pp collisions. This may have observable consequences in dilepton and diphoton experiments.

Comments: LaTeX, 15 pages; revised version to appear in Phys.Rev.D