A Search for the $B^0 \to e^+e^-\gamma$ and $B^0 \to \mu^+\mu^-\gamma$ Decays

Abstract

With the BaBar detector at the PEP-II asymmetric $B$ Factory at SLAC, we present the first search for the decays $B^0\to\ell^+\ell^-\gamma$ ($l=e, \mu$). Using a data set of 292 $fb^{-1}$ collected at the $\Upsilon(4S)$ resonance, we find no significant signal and set the following branching fraction upper limits at 90% confidence level: $\mathcal{B}(B^0\to e^+e^-\gamma)<0.7\times 10^{-7}$ and $\mathcal{B}(B^0\to \mu^+\mu^-\gamma)<3.4\times 10^{-7}$.