363 research outputs found

    Measurements of the Trilinear Gauge Boson Couplings from Diboson Production at D0

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    The most recent measurements of the trilinear gauge boson couplings from the diboson production at the D0 experiment has been presented. The analyzed final states are Zgamma->vvgamma, and WW->lvlv, and WW+WZ->lvjj. We also present results obtained combining all final states involving the W boson. These results represent the most strigent limits set to date at the hadron collider.Comment: 6 pages, 5 figures, To be published in the proceedings of DPF-2009, Detroit, MI, July 2009, eConf C09072

    Studies of Gauge Boson Production with a gamma/gamma-collider at TESLA

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    In absence of the Standard Model Higgs boson the interaction among the gauge bosons becomes strong at high energies and influences the couplings between them. Each trilinear and quartic gauge boson vertex is characterised by a set of couplings which are expected to deviate from their Standard Model values already at energies lower than the energy scale of the New Physics.The precise measurement of gauge boson couplings can provide clues to the mechanism of the electroweak symmetry breaking and their anomalous values can be a sign of a New Physics effect beyond the Standard Model. The estimated precisions of the trilinear gauge boson coupling (TGC) measurements at a photon collider are about one to two orders of magnitude higher than at LEP and Tevatron providing a measurement highly sensitive to the physics beyond the Standard Model. The optimisation of the forward region of the photon collider detector brings the amount of the low-energy background to the manageable level providing a clean environment for the TGC measurements at a photon collider with estimated precisions.Comment: PhD Theses, ~150page

    Search for Violation of CPT and Lorentz Invariance in B s O Meson Oscillations

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    We present the first search for CPT-violating effects in the mixing of B0s mesons using the full Run II data set with an integrated luminosity of 10.4  fb−1 of proton-antiproton collisions collected using the D0 detector at the Fermilab Tevatron Collider. We measure the CPT-violating asymmetry in the decay B0s→μ±D±s as a function of celestial direction and sidereal phase. We find no evidence for CPT-violating effects and place limits on the direction and magnitude of flavor-dependent CPT- and Lorentz-invariance violating coupling coefficients. We find 95% confidence intervals of Δa⊥<1.2×10−12  GeV and (−0.8<ΔaT−0.396ΔaZ<3.9)×10−13  GeV

    Precision measurement of the top-quark mass in lepton+jets final states

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    We measure the mass of the top quark in lepton+jets final states using the full sample of pp¯ collision data collected by the D0 experiment in Run II of the Fermilab Tevatron Collider at s√=1.96  TeV, corresponding to 9.7  fb−1 of integrated luminosity. We use a matrix element technique that calculates the probabilities for each event to result from tt¯ production or background. The overall jet energy scale is constrained in situ by the mass of the W boson. We measure mt=174.98±0.76  GeV. This constitutes the most precise single measurement of the top-quark mass

    Measurement of the Forward-Backward Asymmetry in the Production of B± Mesons in pp¯ Collisions at s√=1.96  TeV

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    We present a measurement of the forward-backward asymmetry in the production of B± mesons, AFB(B±), using B±→J/ψK± decays in 10.4  fb−1 of pp¯ collisions at s√=1.96  TeV collected by the D0 experiment during Run II of the Tevatron collider. A nonzero asymmetry would indicate a preference for a particular flavor, i.e., b quark or b¯ antiquark, to be produced in the direction of the proton beam. We extract AFB(B±) from a maximum likelihood fit to the difference between the numbers of forward- and backward-produced B± mesons. We measure an asymmetry consistent with zero: AFB(B±)=[−0.24±0.41  (stat)±0.19  (syst)]%

    Search for New Fermions (“Quirks”) at the Fermilab Tevatron Collider

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    This is the publisher's version, also available electronically from http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.211803.We report results of a search for particles with anomalously high ionization in events with a high transverse energy jet and large missing transverse energy in 2.4  fb(−1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron pp-bar collider. Production of such particles (quirks) is expected in scenarios with extra QCD-like SU(N) sectors, and this study is the first dedicated search for such signatures. We find no evidence of a signal and set a lower mass limit of 107, 119, and 133 GeV for the mass of a charged quirk with strong dynamics scale Λ in the range from 10 keV to 1 MeV and N=2, 3, and 5, respectively

    Determination of the Width of the Top Quark

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    This is the publisher's version, also available electronically from http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.106.022001

    Search for the Associated Production of a b Quark and a Neutral Supersymmetric Higgs Boson that Decays into τ Pairs

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    This is the publisher's version, also available electronically from http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.104.151801.We report results from a search for production of a neutral Higgs boson in association with a b quark. We search for Higgs decays to τ pairs with one τ subsequently decaying to a muon and the other to hadrons. The data correspond to 2.7  fb(−1) of pp-bar collisions recorded by the D0 detector at s√=1.96  TeV. The data are found to be consistent with background predictions. The result allows us to exclude a significant region of parameter space of the minimal supersymmetric model