5,161 research outputs found

    Search for tb resonances in the leptonic final state with the CMS experiment

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    A search for a W' boson is presented using a dataset corresponding to 5.0 fb−1 of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at √s = 7TeV. The W' to tb decay mode is analyzed leading to a final state signature with a single electron or muon, missing transverse energy, and jets, at least one of which is identified as a b-jet. Different scenarios involving an arbitrary mixture of both left-handed and right-handed chiral projections of the fermions are considered. A W' boson that couples to the right-handed (left-handed) chiral projections of the fermions with the same coupling constants as the Standard Model W boson is excluded for masses below 1.85 (1.51)TeV at the 95% confidence level

    Semileptonic Branching Fraction of Charged and Neutral B Mesons

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    An examination of leptons in Υ(4S){\Upsilon (4S)} events tagged by reconstructed BB decays yields semileptonic branching fractions of b=(10.1±1.8±1.4)%b_-=(10.1 \pm 1.8\pm 1.4)\% for charged and b0=(10.9±0.7±1.1)%b_0=(10.9 \pm 0.7\pm 1.1)\% for neutral BB mesons. This is the first measurement for charged BB. Assuming equality of the charged and neutral semileptonic widths, the ratio b/b0=0.93±0.18±0.12b_-/b_0=0.93 \pm 0.18 \pm 0.12 is equivalent to the ratio of lifetimes. A postscript version is available through World-Wide-Web in http://w4.lns.cornell.edu/public/CLNS/1994Comment: 9 pages (in REVTEX format) Preprint CLNS94-1286, CLEO 94-1

    Precision Measurement of the Ds+Ds+D_s^{*+}- D_s^+ Mass Difference

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    We have measured the vector-pseudoscalar mass splitting M(Ds+)M(Ds+)=144.22±0.47±0.37MeVM(D_s^{*+})-M(D_s^+) = 144.22\pm 0.47\pm 0.37 MeV, significantly more precise than the previous world average. We minimize the systematic errors by also measuring the vector-pseudoscalar mass difference M(D0)M(D0)M(D^{*0})-M(D^0) using the radiative decay D0D0γD^{*0}\rightarrow D^0\gamma, obtaining [M(Ds+)M(Ds+)][M(D0)M(D0)]=2.09±0.47±0.37MeV[M(D_s^{*+})-M(D_s^+)]-[M(D^{*0})-M(D^0)] = 2.09\pm 0.47\pm 0.37 MeV. This is then combined with our previous high-precision measurement of M(D0)M(D0)M(D^{*0})-M(D^0), which used the decay D0D0π0D^{*0}\rightarrow D^0\pi^0. We also measure the mass difference M(Ds+)M(D+)=99.5±0.6±0.3M(D_s^+)-M(D^+)=99.5\pm 0.6\pm 0.3 MeV, using the ϕπ+\phi\pi^+ decay modes of the Ds+D_s^+ and D+D^+ mesons.Comment: 18 pages uuencoded compressed postscript (process with uudecode then gunzip). hardcopies with figures can be obtained by sending mail to: [email protected]

    Observation of a New Charmed Strange Meson

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    Using the CLEO-II detector, we have obtained evidence for a new meson decaying to D0K+D^0 K^+. Its mass is 2573.21.6+1.7±0.8±0.52573.2^{+1.7}_{-1.6}\pm 0.8\pm 0.5 {}~MeV/c2c^2 and its width is 164+5±316^{+5}_{-4}\pm 3~MeV/c2c^2. Although we do not establish its spin and parity, the new meson is consistent with predictions for an L=1L=1, S=1S=1, JP=2+J_P=2^+ charmed strange state.Comment: 9 pages uuencoded compressed postscript (process with uudecode then gunzip). hardcopies with figures can be obtained by sending mail to: [email protected]

    Production and Decay of D_1(2420)^0 and D_2^*(2460)^0

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    We have investigated D+πD^{+}\pi^{-} and D+πD^{*+}\pi^{-} final states and observed the two established L=1L=1 charmed mesons, the D1(2420)0D_1(2420)^0 with mass 242122+1+22421^{+1+2}_{-2-2} MeV/c2^{2} and width 2053+6+320^{+6+3}_{-5-3} MeV/c2^{2} and the D2(2460)0D_2^*(2460)^0 with mass 2465±3±32465 \pm 3 \pm 3 MeV/c2^{2} and width 2876+8+628^{+8+6}_{-7-6} MeV/c2^{2}. Properties of these final states, including their decay angular distributions and spin-parity assignments, have been studied. We identify these two mesons as the jlight=3/2j_{light}=3/2 doublet predicted by HQET. We also obtain constraints on {\footnotesize ΓS/(ΓS+ΓD)\Gamma_S/(\Gamma_S + \Gamma_D)} as a function of the cosine of the relative phase of the two amplitudes in the D1(2420)0D_1(2420)^0 decay.Comment: 15 pages in REVTEX format. hardcopies with figures can be obtained by sending mail to: [email protected]

    Measurement of the Decay Asymmetry Parameters in Λc+Λπ+\Lambda_c^+ \to \Lambda\pi^+ and Λc+Σ+π0\Lambda_c^+ \to \Sigma^+\pi^0

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    We have measured the weak decay asymmetry parameters (\aLC ) for two \LC\ decay modes. Our measurements are \aLC = -0.94^{+0.21+0.12}_{-0.06-0.06} for the decay mode Λc+Λπ+\Lambda_c^+ \to \Lambda\pi^+ and \aLC = -0.45\pm 0.31 \pm 0.06 for the decay mode ΛcΣ+π0\Lambda_c \to \Sigma^+\pi^0 . By combining these measurements with the previously measured decay rates, we have extracted the parity-violating and parity-conserving amplitudes. These amplitudes are used to test models of nonleptonic charmed baryon decay.Comment: 11 pages including the figures. Uses REVTEX and psfig macros. Figures as uuencoded postscript. Also available as http://w4.lns.cornell.edu/public/CLNS/1995/CLNS95-1319.p

    Measurement of the branching fraction for Υ(1S)τ+τ\Upsilon (1S) \to \tau^+ \tau^-

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    We have studied the leptonic decay of the Υ(1S)\Upsilon (1S) resonance into tau pairs using the CLEO II detector. A clean sample of tau pair events is identified via events containing two charged particles where exactly one of the particles is an identified electron. We find B(Υ(1S)τ+τ)=(2.61 ± 0.12 +0.090.13)B(\Upsilon(1S) \to \tau^+ \tau^-) = (2.61~\pm~0.12~{+0.09\atop{-0.13}})%. The result is consistent with expectations from lepton universality.Comment: 9 pages, RevTeX, two Postscript figures available upon request, CLNS 94/1297, CLEO 94-20 (submitted to Physics Letters B

    Search for New Physics with Jets and Missing Transverse Momentum in pp collisions at sqrt(s) = 7 TeV

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    A search for new physics is presented based on an event signature of at least three jets accompanied by large missing transverse momentum, using a data sample corresponding to an integrated luminosity of 36 inverse picobarns collected in proton--proton collisions at sqrt(s)=7 TeV with the CMS detector at the LHC. No excess of events is observed above the expected standard model backgrounds, which are all estimated from the data. Exclusion limits are presented for the constrained minimal supersymmetric extension of the standard model. Cross section limits are also presented using simplified models with new particles decaying to an undetected particle and one or two jets

    Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV