Axial anomaly, vector meson dominance and π0 → γγ at finite temperature

A thermal Finite Energy QCD Sum Rule is used to determine the temperature behaviour of the omega rho pi strong coupling. This coupling decreases with increasing T and vanishes at the critical temperature, a likely signal for quark deconfinement. This is then used in the Vector Meson Dominance (VMD) expression for the pi(0) --> gamma gamma amplitude, which is also found to vanish at the critical temperature, as expected. This result supports the validity of VMD at T not equal 0. However, if VMD would not hold at finite temperature, then there is no prediction for the pi(0) --> gamma gamma amplitude. (C) 2000 Elsevier Science B.V. All rights reserved.