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T-dependence of η' and η masses and the restorations of the U_A(1) and the SU_A(3) chiral symmetry

The approach to the η'-η complex using chirally well-behaved quark-antiquark pseudoscalar bound-state solutions and incorporating the non-Abelian axial anomaly of QCD through the generalization of the Witten-Veneziano relation, is extended to finite temperatures. Employing the chiral condensate has led to a sharp chiral and U_A(1) symmetry restoration. However, with the condensates of quarks with realistic explicit chiral symmetry breaking, which exhibit a smooth, crossover chiral symmetry restoration in qualitative agreement with lattice QCD results, we get a crossover U_A(1) transition, with smooth and gradual melting of anomalous mass contributions. This way we obtain a substantial drop of the η' mass around the chiral transition temperature, but no η mass drop, in agreement with the present empirical evidence.

U_A(1) and SU_A(3) chiral symmetry ; QCD ; η' ; η mesons ; temperature dependence

Mrežna stranica skupa Day of Femtoscopy (A femtoszkópia napja) 2019: https://indico.cern.ch/event/858268/