B Decays at Babar

We present branching fraction and CP asymmetry results for a variety of B decays based on up to 56.4 fb −1 collected by the BABAR experiment running near the Υ (4S) resonance at the PEP-II e + e − B-factory. The results presented in this paper are based on an integrated luminosity of up to 56.4 fb −1 collected at the Υ (4S) resonance with the BABAR detector [1] at the PEP-II asymmetric e + e − col-lider at the Stanford Linear Accelerator Center. Charged particle track parameters are measured by a five-layer double-sided silicon vertex tracker and a 40-layer drift chamber located in a 1.5-T magnetic field. Charged particle identification is achieved with an internally reflecting ring imaging Cherenkov detector (DIRC) and from the average dE/dx energy loss measured in the tracking devices. Photons and π 0 s are detected with an electromagnetic calorimeter (EMC) consisting of 6580 CsI(Tl) crystals. An instrumented flux return (IFR), containing multiple layers of re-sistive plate chambers, provides muon and long-lived hadron identification. The B meson candidates are identified kine-matically using two independent variables. The first is ∆E = E * − E * beam , which is peaked at zero for signal events, since the energy of the B candidate in the Υ (4S) rest frame, E * , must be equal to the energy of the beam, E * beam , by energy conservation. The second is the beam-energy substituted mass, m ES = (E * 2 beam − p * 2 B), where p * B is the momentum of the B meson in the Υ (4S) rest frame, and must be close to the nominal B mass [5]. The resolution of m ES is dominated by the beam energy spread and is approximately 2.5 MeV/c 2. Several of the B modes presented here have decays that involve neutral pions (π 0) and K 0 S particles. Neutral pion candidates are formed by combining pairs of photons in the EMC, with requirements made to the energies of the photons and the mass and energy of the π 0. Table 1 shows these requirements for various decay modes, as well as the selection requirements for K 0 S candidates , which are made by combining oppositely charged pions. Significant backgrounds from light quark-antiquark continuum events are suppressed using various event shape variables which exploit the difference in the event topologies in the …