Measurement of B+ -> K+ tau- tau+, B -> K* l+ l- and B -> K pi+ pi- gamma decays 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+ tau- tau+ and we do not find evidence for signal. The measured branching fraction is (1.31+0.66-0.61(stat.)+0.35-0.25(sys.)) x 10-3 with an upper limit, at the 90% confidence level, of B(B+ -> K+ tau+ tau-) < 2.25 x 10-3. We then study the lepton forward-backward asymmetry AFB and the longitudinal K* polarization FL in the rare decays B -> K* l+ l-, where l+ l- is either e+ e- or mu+ mu-. We report results for both the K*(892)0l+l- and K*(892)+l+l- final states, as well as their combination K*l+l-, in five disjoint dilepton mass-squared bins. Finally, we measure the time-dependent CP asymmetry in the radiative-penguin decay B0 -> KS0 pi- pi+ gamma. The Kpipi resonant structure is extracted by an amplitude analysis of the m_Kpipi and m_Kpi spectra in B+ -> K+ pi- pi+ gamma decays. We use these results to extract the mixing-induced CP parameters of the process B0 -> KS rho gamma from the time-dependent analysis of B0 -> KS0 pi+ pi- gamma decays and obtain S = -0.18 pm 0.32(stat.) +0.06 -0.05(syst.).