In a data sample of approximately 1.3 fb-1 collected with the D0 detector between 2002 and 2006, the orbitally excited charm state D_s1(2536) has been observed with a measured mass of 2535.7 +/- 0.6 ...(stat) +/- 0.5 (syst) MeV via the decay mode B0_s -> D_s1(2536) mu nu X. A first measurement is made of the branching ratio product Br(b(bar) -> D_s1(2536) mu nu X).Br(D_s1(2536)->D* K0_S). Assuming that D_s1(2536) production in semileptonic decay is entirely from B0_s, an extraction of the semileptonic branching ratio Br(B0_s -> D_s1(2536) mu nu X) is made.
We present the first measurement of dijet angular distributions in ppbar collisions at sqrt{s}=1.96TeV at the Fermilab Tevatron Collider. The measurement is based on a dataset corresponding to an ...integrated luminosity of up to 0.7fb-1 collected with the D0 detector. Dijet angular distributions have been measured over a range of dijet masses, from 0.25TeV to above 1.1TeV. The data are in good agreement with the predictions of perturbative QCD and are used to constrain new physics models including quark compositeness, large extra dimensions, and TeV-1 scale extra dimensions. For all models we set the most stringent direct limits to date.
We report on a first search for production of Higgs bosons decaying into neutral long-lived particles (NLLP) which each decay to a bbbar pair, using 3.6 fb^-1 of data recorded with the D0 detector at ...the Fermilab Tevatron collider. We search for pairs of displaced vertices in the tracking detector at radii in the range 1.6--20 cm from the beam axis. No significant excess is observed above background, and upper limits are set on the production rate in a hidden-valley benchmark model for a range of Higgs boson masses and NLLP masses and lifetimes.
We report on a first search for production of the lightest neutral CP-even Higgs boson (h) in the next-to-minimal supersymmetric standard model, where h decays to a pair of neutral pseudoscalar Higgs ...bosons (a), using 4.2/fb of data recorded with the D0 detector at Fermilab. The a bosons are required to either both decay to mu^+mu^- or one to mu^+mu^- and the other to tau^+tau^-. No significant signal is observed, and we set limits on its production as functions of M_a and M_h.
We combine the D0 measurement of the width difference between the light and heavy B_s^0 mass eigenstates and of the CP-violating mixing phase determined from the time-dependent angular distributions ...in the B_s -> J/psi phi decays along with the charge asymmetry in semileptonic decays also measured with the D0 detector. With the additional constraint from the world average of the flavor-specific B_s^0 lifetime, we obtain Delta Gamma_s = (\Gamma_L - \Gamma_H) = 0.13 +- 0.09 ps\(^{-1}\) and phi_s = -0.70 ^{+0.47}_{-0.39}. The data sample corresponds to an integrated luminosity of 1.1 fb^{-1} accumulated with the D0 detector at the Fermilab Tevatron Collider.
We present cross section measurements for Z/gamma*+jets+X production, differential in the transverse momenta of the three leading jets. The data sample was collected with the D0 detector at the ...Fermilab Tevatron proton anti-proton collider at a center-of-mass energy of 1.96 TeV and corresponds to an integrated luminosity of 1 fb-1. Leading and next-to-leading order perturbative QCD predictions are compared with the measurements, and agreement is found within the theoretical and experimental uncertainties. We also make comparisons with the predictions of four event generators. Two parton-shower-based generators show significant shape and normalization differences with respect to the data. In contrast, two generators combining tree-level matrix elements with a parton shower give a reasonable description of the the shapes observed in data, but the predicted normalizations show significant differences with respect to the data, reflecting large scale uncertainties. For specific choices of scales, the normalizations for either generator can be made to agree with the measurements.
A search for pair production of first-generation leptoquarks LQ is performed with data collected by the D0 experiment in p pbar collisions at sqrt(s)=1.96 TeV at the Fermilab Tevatron Collider. In a ...sample of data corresponding to ~1 fb-1, the search has been performed on the final states with two electrons and two jets or one electron, two jets and missing transverse energy. We find our data consistent with standard model expectations. The results are combined with those found in a previous analysis of events with two jets and missing transverse energy to obtain scalar LQ mass limits. We set 95% C.L. lower limits on a scalar LQ mass of 299 GeV, 284 GeV and 216 GeV for beta=1, beta=0.5 and beta=0.02 respectively, where beta is the LQ branching ratio in the eq channel. This improves the results obtained with a lower luminosity sample from Run II of the Tevatron. Lower limits on vector LQ masses with different couplings from 357 GeV to 464 GeV for beta=0.5 are also set using this analysis.
A search for the pair production of scalar top quarks, or stops, has been performed in 360 pb-1 of data from p pbar collisions at a center-of-mass energy of 1.96 TeV, collected by the D0 detector at ...the Fermilab Tevatron collider. The stop decay mode considered is stop into c chi, where chi is the lightest supersymmetric particle. The topology analyzed therefore consists of a pair of acoplanar heavy-flavor jets with missing transverse energy. The data and standard model expectation are in agreement, and a 95% C.L. exclusion domain in the stop and chi mass plane has been determined, extending the domain excluded by previous experiments.
We report a measurement of the \(B^0_{s}\) lifetime in the semileptonic decay channel \(B^0_{s}\to D^-_s \mu^{+}\nu X\) (and its charge conjugate), using approximately 0.4 fb\(^{-1}\) of data ...collected with the D0 detector during 2002 -- 2004. We have reconstructed 5176 \(D^-_s \mu^{+}\) signal events, where the \(D_s^-\) is identified via the decay \(D_s^-\to \phi\pi^-\), followed by \(\phi\to K^+ K^-\). Using these events, we have measured the \(B^0_s\) lifetime to be \(\tau(B^0_{s}) = 1.398 \pm 0.044\) \(({stat}) ^{+0.028}_{-0.025}\) \(({syst}) {ps}\). This is the most precise measurement of the \(B_s^0\) lifetime to date.
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