Search for the rare decay $D^0\to {\hat{I}}^3{\hat{I}}^3$ at Belle

Abstract

We search for the rare radiative decay $D^0\to {\hat{I}}^3{\hat{I}}^3$ using a data sample with an integrated luminosity of $832\mathrm{f}{\mathrm{b}}^{-1}$ 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 $\mathcal{B}(D^0\to {\hat{I}}^3{\hat{I}}^3)<8.5\times 10^{-7}$ at $90\%$ confidence level. This is the most restrictive limit on the decay channel to date.