Modulo the scale of spontaneous breaking of Peccei-Quinn symmetry, the axion mass $m_a(T)$ is given by the QCD topological susceptibility ${ \chi}(T)$ at all temperatures $T$. From an approach tying the $U_A(1)$ and chiral symmetry breaking and getting good $T$-dependence of ${ \eta}$ and ${ \eta}$ mesons, we get ${ \chi}(T)$ for an effective Dyson-Schwinger model of nonperturbative QCD. Comparison with lattice results for ${ \chi}(T)$, and thus also for $m_a(T)$, shows good agreement for temperatures ranging from zero up to the double of the chiral restoration temperature $T_c$.
Categories: hep-ph nucl-th