Improved upper limit on flavor-changing neutral-current decays of thebquark

Abstract

We report the results of a new search for flavor-changing neutral-current decays of the b quark and present a 90%-confidence-level upper limit for the branching fraction for B→$l^{+}$ $l^{\mathrm{-}}$X of 1.2×${10}^{\mathrm{-}3}$.