Recent progress on the rare decay KL to pi0 mu+ mu-
  The rare decay KL to pi0mu+mu- has a significant CP-conserving contribution. The reliable theoretical estimation of this piece from the experimental pi0-two photon branching ratio is shortly reviewed. Then, we discuss the exceptional sensitivity of the combined set of decays, into pi0 nu nubar, pi0e+e- and pi0mu+mu-, to New Physics signal, and also, interestingly, to New Physics nature. 
Christopher Smith