$\Sigma^{+}\to p \mu^{+}\mu^{-}$ in the Standard Model

The HyperCP collaboration has recently reported the observation of three events for the mode $\Sigma^{+}\to p \mu^{+}\mu^{-}$. They have suggested that new physics may be required to understand the implied decay rate and the observed $M_{\mu\mu}$ distribution. Motivated by this result, we re-examine this mode within the Standard Model. The result is long distance dominated and we estimate it with the aid of chiral perturbation theory.