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How, how much, and when are U_A (1) and chiral symmetry restored: T-dependence of axions, η and η'

We express the QCD topological susceptibility χ(T) through quark condensates calculated in two effective Dyson-Schwinger models of nonperturbative QCD. They exhibit the correct chiral behavior, including the dynamical breaking of chiral symmetry and its restoration at high temperature T. This is reflected in the U_A(1) symmetry breaking and restoration through χ(T), which yields the T-dependence of the U_A(1)-anomaly-influenced masses of η' and η mesons consistent with experiment. This in turn supports our prediction for the T- dependence of the axion mass. Another support is a rather good agreement with the pertinent lattice results.

QCD topological susceptibility ; temperature dependence ; axion, η' and η meson masses, axial anomaly ; chiral symmetry restoration

Mrežna stranica skupa 19th ZIMÁNYI SCHOOL - Winter Workshop on Heavy Ion Physics: http://zimanyischool.kfki.hu/19/