Unitarity and vector meson contributions to K^+ -> pi^+ gamma gamma

Abstract

We compute the one-loop unitarity corrections O(p^6) from K^+ -> pi^+ pi^+ pi^- to K^+ -> pi^+ gamma gamma and we find they are relevant, increasing the leading order prediction for the width in a 30-40%. The contributions of local O(p^6) amplitudes, generated by vector meson exchange, are discussed in several models and we conclude that the vector resonance contribution should be negligible compared to the unitarity corrections.

Comments: 15 pages, LaTex, 4 figures included as PS files, uuencoded with uufiles, submitted to Phys. Lett. B