Search for the rare decay D0 →γγ at Belle

Abstract

We search for the rare radiative decay D0→γγ using a data sample with an integrated luminosity of 832 fb-1 recorded by the Belle detector at the KEKB e+e- asymmetric-energy collider. We find no statistically significant signal and set an upper limit on the branching fraction of B(D0→γγ)<8.5×10-7 at 90% confidence level. This is the most restrictive limit on the decay channel to date.