K_S\rightarrow \gamma\gamma , K_L\rightarrow\pi^0\gamma\gamma$ and Unitarity

Abstract

Agreement between the experimental value $\Gamma (K_S\to \gamma \gamma )$ and the number predicted via a one-loop chiral perturbation theory calculation has been cited as a success for the latter. On the other hand the one-loop prediction for the closely related process $K_L\to {\pi }^0\gamma \gamma$ has been found to be a factor three below the experimental value. Using the inputs of unitarity and dispersion relations, we demonstrate the importance of higher order loop effects to both of these processes.

Comments: 20 pages (4 figures available on request), UMHEP-397