ANOMALOUS PION DECAY IN EFFECTIVE QCD AT FINITE-TEMPERATURE

The width of the process pi(0) --> gamma gamma is calculated within ef fective QCD at finite temperature. We use two different effective mode ls which describe chiral symmetry breaking and its restoration at fini te temperature in SU(2)(f): (i) an effective lagrangian with a nonloca l separable interaction kernel, (ii) A- and B-scaled NJL lagrangians w hich 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 thre shold. 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-->gamm a 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 suppress ed 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 appro ach.