Anomalous pion decay in effective QCD at finite temperature

The width of the process π0 → γγ is calculated within effective QCD at finite temperature. We use two different effective models which describe chiral symmetry breaking and its restoration at finite temperature in SU(2)ƒ: (i) an effective lagrangian with a nonlocal separable interaction kernel, (ii) A- and B-scaledNJL lagrangians which implement the scale anomaly of QCD. We calculate the temperature dependences of the quark and pion masses as well as of the pion-park-antiquark coupling strength below and above the double quark mass threshold. At zero temperature we obtain a fairly good agreement with the experimental value for the decay width. The temperature dependence of the decay width is related to that of the pion mass. Γπ0 → γγ is enhanced in the vicinity of the Mott temperature (Mπ = 2mq) for the nonlocal as well as for the A-scaled model and suppressed for the B-scaled model. We compare our results with the SU(2) Nambu-Jona-Lasinio model which is contained as a limiting case in our approach.