We have searched for a heavy resonance decaying into a Z+jet final state in p-pbar collisions at a center of mass energy of 1.96 TeV at the Fermilab Tevatron collider using the D0 detector. No ...indication for such a resonance was found in a data sample corresponding to an integrated luminosity of 370/pb. We set upper limits on the cross section times branching fraction for heavy resonance production at the 95% C.L. as a function of the resonance mass and width. The limits are interpreted within the framework of a specific model of excited quark production.
We measure the dimuon charge asymmetry A in pp(bar) collisions at a center of mass energy sqrt{s} = 1960 GeV. The data was recorded with the D0 detector and corresponds to an integrated luminosity of ...approximately 1.0 fb-1. Assuming that the asymmetry A is due to asymmetric B^0 <-> B(bar)^0 mixing and decay, we extract the CP-violation parameter of B^0 mixing and decay: Re(epsilon_B^0)(1 + |epsilon_B^0|^2) = A_B^0/4 = -0.0023 +/- 0.0011 (stat) +/- 0.0008 (syst). A_B^0 is the dimuon charge asymmetry from decays of B^0 B(bar)^0 pairs. The general case, with CP violation in both B^0 and B_s^0 systems, is also considered. Finally we obtain the forward-backward asymmetry that quantifies the tendency of mu+ to go in the proton direction and mu- to go in the anti-proton direction. The results are consistent with the standard model and constrain new physics.
We report a new measurement of the ttbar production cross section in pbarp collisions at a center-of-mass energy of 1.96 TeV using events with one charged lepton (electron or muon), missing ...transverse energy, and jets. Using 425 pb^{-1} of data collected using the D0 detector at the Fermilab Tevatron Collider, and enhancing the ttbar content of the sample by tagging b jets with a secondary vertex tagging algorithm, the ttbar production cross section is measured to be: 6.6 \pm 0.9 (stat+syst) \pm 0.4 (lum) pb. This cross section is the most precise D0 measurement to date for ttbar production and is in good agreement with standard model expectations.
We present a search for the flavor-changing neutral current decay B0_s -> phi mu+ mu- using about 0.45 fb^-1 of data collected in p \bar p collisions at sqrt{s} =1.96 TeV with the D{\O}detector at ...the Fermilab Tevatron Collider. We find an upper limit on the branching ratio of this decay normalized to B0_s -> J/psi phi of B(B0_s -> phi mu+ mu-)/B(B0_s -> J/psi phi) < 4.4\times 10^{-3} at the 95% C.L. Using the central value of the world average branching fraction of B0_s -> J/psi phi, the limit corresponds to B(B0_s -> phi mu+ mu-) < 4.1 \times 10^{-6} at the 95% C.L., the most stringent upper bound to date.
Limits are set on anomalous WWgamma and WWZ trilinear gauge couplings using W+W- -> e+e-, W+W- -> e mu, and W+W- -> mu+mu- events. The data set was collected by the Run II D0 detector at the Fermilab ...Tevatron Collider and corresponds to approximately 250 inverse pb of integrated luminosity at sqrt(s) = 1.96 TeV. Under the assumption that the WWgamma couplings are equal to the WWZ couplings and using a form factor scale of Lambda = 2.0 TeV, the combined 95% C.L. one-dimensional coupling limits from all three channels are -0.32 < Delta kappa < 0.45 and -0.29 < lambda < 0.30.
We present the results of a search for the production of an excited state of the muon, mu*, in proton antiproton collisions at sqrt s = 1.96 TeV. The data have been collected with the D0 experiment ...at the Fermilab Tevatron Collider and correspond to an integrated luminosity of approximately 380 pb^-1. We search for mu* in the process p pbar -> mu* mu, with the mu* subsequently decaying to a muon plus photon. No excess above the standard model expectation is observed in data. Interpreting our data in the context of a model that describes mu* production by four-fermion contact interactions and mu* decay via electroweak processes, we exclude production cross sections higher than 0.057 pb -- 0.112 pb at the 95% confidence level, depending on the mass of the excited muon. Choosing the scale for contact interactions to be Lambda = 1 TeV, excited muon masses below 618 GeV are excluded.
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