A. Gresele

Measurement of the Forward-Backward Asymmetry in the B{yields}K{sup (*)}{mu}{sup +}{mu}{sup -} Decay and First Observation of the B{sub s}{sup 0}{yields}{phi}{mu}{sup +}{mu}{sup -} Decay

We reconstruct the rare decays B{sup +}{yields}K{sup +}{mu}{sup +}{mu}{sup -}, B{sup 0}{yields}K{sup *}(892){sup 0}{mu}{sup +}{mu}{sup -}, and B{sub s}{sup 0}{yields}{phi}(1020){mu}{sup +}{mu}{sup -} in a data sample corresponding to 4.4 fb{sup -1} collected in pp collisions at {radical}(s)=1.96 TeV by the CDF II detector at the Tevatron Collider. Using 121{+-}16 B{sup +}{yields}K{sup +}{mu}{sup +}{mu}{sup -} and 101{+-}12 B{sup 0}{yields}K*{sup 0}{mu}{sup +}{mu}{sup -} decays we report the branching ratios. In addition, we report the differential branching ratio and the muon forward-backward asymmetry in the B{sup +} and B{sup 0} decay modes, and the K{sup *0} longitudinal polarization fraction in the B{sup 0} decay mode with respect to the squared dimuon mass. These are consistent with the predictions, and most recent determinations from other experiments and of comparable accuracy. We also report the first observation of the B{sub s}{sup 0}{yields}{phi}{mu}{sup +}{mu}{sup -} decay and measure its branching ratio BR(B{sub s}{sup 0}{yields}{phi}{mu}{sup +}{mu}{sup -})=[1.44{+-}0.33{+-}0.46]x10{sup -6} using 27{+-}6 signal events. This is currently the most rare B{sub s}{sup 0} decay observed.

Search for the supersymmetric partner of the top quark in pp collisions at {radical}(s)=1.96 TeV

We present a search for the lightest supersymmetric partner of the top quark in proton-antiproton collisions at a center-of-mass energy root s = 1: 96 TeV. This search was conducted within the framework of the R parity conserving minimal supersymmetric extension of the standard model, assuming the stop decays dominantly to a lepton, a sneutrino, and a bottom quark. We searched for events with two oppositely-charged leptons, at least one jet, and missing transverse energy in a data sample corresponding to an integrated luminosity of 1 fb(-1) collected by the Collider Detector at Fermilab experiment. No significant evidence of a stop quark signal was found. Exclusion limits at 95% confidence level in the stop quark versus sneutrino mass plane are set. Stop quark masses up to 180 GeV/c(2) are excluded for sneutrino masses around 45 GeV/c(2), and sneutrino masses up to 116 GeV/c(2) are excluded for stop quark masses around 150 GeV/c(2).