B- > K tau tau, B - >K pi pi gamma and B -> K* l l at BaBar

Abstract

We present some recent measurements of rare flavor-changing neutral current B decays, using data collected with the BABAR detector at the PEP-II e + e − collider at SLAC. First, we search for the rare process B + → K + τ + τ − and we do not find evidence for a signal. The measured branching fraction is (1.31 +0.66 −0.61 (stat.) +0.35 −0.25 (sys.)) × 10 −3 with an upper limit, at the 90% confidence level, of B(B → K + τ + τ −) < 2.25 × 10 −3. We then study the lepton forward-backward asymmetry A FB and the longitudinal K * polarization F L in the rare decays B → K * l + l − , where l + l − is either * Speaker. † on behalf of the BABAR collaboration