First Results in Exclusive Radiative Penguin Decays at BABAR

Abstract

We present a preliminary measurement of the branching fraction of the exclusive penguin decay B^0 -> K^*0 gamma using (8.6+/-0.3) x 10^6 B-anti-B decays BF(B^0 -> K^*0 gamma) = (5.2+/-0.82 (stat.) +/- 0.47 (sys.)) x 10^-5. In addition we search for the related penguin decays with a lepton pair in the final state, B^+ -> K^+ l^+l^-, B^0 -> K^*0 l^+l^-. We find no evidence for these decays in 3.7+/-0.1 x 10^6 B-anti-B decays and set preliminary 90% C.L upper limits of BF(B^+ -> K^+ e^+ e^-) < 12.5 x 10^{-6}, BF(B^+ -> K^+ mu^+ mu^-) < 8.3 x 10^{-6}, BF(B^0 -> K^*0 e^+ e^-) < 24.1 x 10^{-6}, BF(B^0 -> K^*0 mu^+ mu^-) < 24.5 x 10^{-6}.