Search for a dark photon at BABAR

We present the results of a search for a dark photon decaying to $e^{+}{e}^{-}$ or ${\mu }^{+}{\mu }^{-}$ in the \babar\ detector. We find no evidence for such a dark photon and set upper limits on the dark mixing as a function mass, tightening the constraints on the parameter space of several dark sector theories.