HIGGS DECAY INTO 2 PHOTONS, DISPERSION-RELATIONS AND TRACE ANOMALY

We examine the contribution of W boson loops to the amplitude of the p rocess H --> gamma gamma within the dispersion relation approach, taki ng up an issue raised in this context recently. We show that the non-v anishing limit of the relevant form factor for m(w) --> 0 is due to a finite subtraction induced by the value of the corresponding trace ano maly. The argument can be turned around and one thus arrives at a disp ersive (''infrared'') derivation of the trace anomaly.