  Recent RHIC results on eta' multiplicity in heavy-ion collisions are of great
importance because they clearly signal a partial restoration of U_A(1) symmetry
at high temperatures T, and thus provide an unambiguous signature of the
formation of a new state of matter. Prompted by these experimental results of
STAR and PHENIX collaborations, we discuss and propose the minimal
generalization of the Witten-Veneziano relation to finite T.
