Search for the Lepton Flavour Violating decays ${\rm Y}(2S)\to e^{\pm }{\mu }^{\mp }$ and ${\rm Y}(3S)\to e^{\pm }{\mu }^{\mp }$

Abstract

Charged lepton flavour violating processes are unobservable in the standard model, but they are predicted to be enhanced in several new physics extensions. We present the results of a search for ${\rm Y}(2S)$ and ${\rm Y}(3S)$ decays to $e^{\pm }{\mu }^{\mp }$ decays. The search was conducted using data samples consisting of 99 million ${\rm Y}(2S)$ and 122 million ${\rm Y}(3S)$ mesons, collected at center-of-mass energies of 10.02 and 10.36 GeV, respectively, by the BABAR detector at the SLAC PEP-II $e^{+}{e}^{-}$ collider.