ANOMALOUS PION DECAY IN EFFECTIVE QCD AT FINITE-TEMPERATURE

The width of the process pi(0) --> gamma gamma 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)(f): (i) an effective lagrangian with a nonlocal separable interaction kernel, (ii) A- and B-scaled NJL 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-quark-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. Gamma(pi 0-->gamma gamma) is enhanced in the vicinity of the Mott temperature (M(pi) = 2m(q)) 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.