Renormalizing a three-flavor lattice calculation of the two-photon contribution to $K_L\to {\mu }^{+}{\mu }^{-}$

En-Hung Chao, Norman Christ, Ceran Hu

The Standard Model prediction for the rare $K_L\to {\mu }^{+}{\mu }^{-}$ decay depends critically on the long-distance contribution coming from the exchange of two photons. Such a contribution ca…