6,320 research outputs found

    Precision measurements of the top quark mass from the Tevatron in the pre-LHC era

    Full text link
    The top quark is the heaviest of the six quarks of the Standard Model. Precise knowledge of its mass is important for imposing constraints on a number of physics processes, including interactions of the as yet unobserved Higgs boson. The Higgs boson is the only missing particle of the Standard Model, central to the electroweak symmetry breaking mechanism and generation of particle masses. In this Review, experimental measurements of the top quark mass accomplished at the Tevatron, a proton-antiproton collider located at the Fermi National Accelerator Laboratory, are described. Topologies of top quark events and methods used to separate signal events from background sources are discussed. Data analysis techniques used to extract information about the top mass value are reviewed. The combination of several most precise measurements performed with the two Tevatron particle detectors, CDF and \D0, yields a value of \Mt = 173.2 \pm 0.9 GeV/c2c^2.Comment: This version contains the most up-to-date top quark mass averag

    Flavor-Specific Inclusive B Decays to Charm

    Get PDF
    We have measured the branching fractions for B -> D_bar X, B -> D X, and B -> D_bar X \ell^+ \nu, where ``B'' is an average over B^0 and B^+, ``D'' is a sum over D^0 and D^+, and``D_bar'' is a sum over D^0_bar and D^-. From these results and some previously measured branching fractions, we obtain Br(b -> c c_bar s) = (21.9 ±\pm 3.7)%, Br(b -> s g) K^- \pi^+) = (3.69 ±\pm 0.20)%. Implications for the ``B semileptonic decay problem'' (measured branching fraction being below theoretical expectations) are discussed. The increase in the value of Br(b -> c c_bar s) due to B>DXB -> D X eliminates 40% of the discrepancy.Comment: 12 page postscript file, postscript file also available through http://w4.lns.cornell.edu/public/CLN

    Further Search for the Two-Photon Production of the Glueball Candidate fJ(2220)f_{J}(2220)

    Get PDF
    The CLEOII detector at the Cornell e+ e- storage ring CESR has been used to search for the two-photon production of the fJ(2220)f_J(2220) decaying into pi+ pi-. No evidence for a signal is found in data corresponding to an integrated luminosity of 4.77/fb and a 95% CL upper limit on ΓtwophotonBRpi+pi\Gamma_{two-photon} * BR{pi+ pi-} of 2.5 eV is set. If this result is combined with the BES Collaboration's measurement of fJ(2220)>pi+pif_J(2220) -> pi+ pi- in radiative J/ψJ/\psi decay, a 95% CL lower limit on the stickiness of the fJ(2220)f_J(2220) of 73 is obtained. If the recent CLEO result for \Gamma_{two-photon} * BR{\K_S K_S} is combined with the present result, the stickiness of the fJ(2220)f_J(2220) is found to be larger than 102 at the 95% CL. These results for the stickiness (the ratio of the probabilities for two-gluon coupling and two-photon coupling) provide further support for a substantial neutral parton content in the fJ(2220)f_J(2220).Comment: 8 pages, postscript file also available through http://w4.lns.cornell.edu/public/CLN

    Search for the Decay τ4pi3π+(π0)ντ\tau^{-}\to 4pi^{-}3\pi^{+}(\pi^{0})\nu_{\tau}

    Full text link
    We have searched for the decay of the tau lepton into seven charged particles and zero or one pi0. The data used in the search were collected with the CLEO II detector at the Cornell Electron Storage Ring (CESR) and correspond to an integrated luminosity of 4.61 fb^(-1). No evidence for a signal is found. Assuming all the charged particles are pions, we set an upper limit on the branching fraction, B(tau- -> 4pi- 3pi+ (pi0) nu_tau) < 2.4 x 10^(-6) at the 90% confidence level. This limit represents a significant improvement over the previous limit.Comment: 9 page postscript file, postscript file also available through http://w4.lns.cornell.edu/public/CLN

    Limit on the Two-Photon Production of the Glueball Candidate fJ(2220)f_{J}(2220) at CLEO

    Full text link
    We use the CLEO detector at the Cornell electron-positron storage ring, CESR, to search for the two-photon production of the glueball candidate f_J(2220) in its decay to K_s K_s. We present a restrictive upper limit on the product of the two-photon partial width and the K_s K_s branching fraction. We use this limit to calculate a lower limit on the stickiness, which is a measure of the two-gluon coupling relative to the two-photon coupling. This limit on stickiness indicates that the f_J(2220) has substantial glueball content.Comment: 9 page postscript file, postscript file also available through http://w4.lns.cornell.edu/public/CLN

    Tau Neutrino Helicity from h±h^{\pm} Energy Correlations

    Full text link
    We report a measurement of the magnitude of the tau neutrino helicity from tau-pair events taken with the CLEO detector at the CESR electron-positron storage ring. Events in which each tau undergoes the decay tau -> h nu, with h a charged pion or kaon, are analyzed for energy correlations between the daughter hadrons, yielding |xi| = 2*|h_nu| = 1.03 +/- 0.06 +/- 0.04, with the first error statistical and the second systematic.Comment: 11 pages, postscript file also available through http://w4.lns.cornell.edu/public/CLN

    Observation of the Isospin-Violating Decay Ds+Ds+π0D_s^{*+}\to D_s^+\pi^0

    Full text link
    Using data collected with the CLEO~II detector, we have observed the isospin-violating decay Ds+Ds+π0D_s^{*+}\to D_s^+\pi^0. The decay rate for this mode, relative to the dominant radiative decay, is found to be Γ(Ds+Ds+π0)/Γ(Ds+Ds+γ)=0.0620.018+0.020±0.022\Gamma(D_s^{*+}\to D_s^+\pi^0)/\Gamma(D_s^{*+}\to D_s^+\gamma)= 0.062^{+0.020}_{-0.018}\pm0.022.Comment: 8 page uuencoded postscript file, also available through http://w4.lns.cornell.edu/public/CLN
    corecore