We report the results of a search for a narrow resonance decaying into two photons in 1.1 fb-1 of data collected by the D0 experiment at the Fermilab Tevatron Collider during the period 2002–2006. We ...find no evidence for such a resonance and set a lower limit on the mass of a fermiophobic Higgs boson of mhf > 100 GeV at the 95% C.L. This exclusion limit exceeds those obtained in previous searches at the Fermilab Tevatron and covers a significant region of the parameter space B(hf to gammagamma)vsmhf which was not accessible at the CERN large electron-positron collider.
From an analysis of the flavor-tagged decay \bsdec we obtain the width difference between the $B_s^0$ light and heavy mass eigenstates, $\Delta \Gamma_s \equiv \Gamma_L - \Gamma_H = 0.19 \pm 0.07 ...{\rm (stat)}\thinspace ^{+0.02}_{-0.01} {\rm (syst)}$ ps$^{-1}$, and the CP-violating phase, $\phi_{s} =-0.57 ^{+0.24}_{-0.30} {\rm (stat)}\thinspace ^{+0.07}_{-0.02} {\rm (syst)}$. The allowed 90% C.L. intervals of $\Delta \Gamma_s$ and $\phi_s$ are $0.06 <\Delta \Gamma_s <0.30$ ps$^{-1}$ and $-1.20 <\phi_s < 0.06$, respectively. The data sample corresponds to an integrated luminosity of 2.8 fb$^{-1}$ accumulated with the D0 detector at the Fermilab Tevatron collider.
We present a study of the polarization of the $\Upsilon(1S)$ and $\Upsilon(2S)$ states using a $1.3 $ fb$^{-1}$ data sample collected by the D0 experiment in 2002--2006 during Run II of the Fermilab ...Tevatron Collider. We measure the polarization parameter $\alpha=(\sigma_{T}-2\sigma_{L})/(\sigma_{T}+2\sigma_{L})$, where $\sigma_{T}$ and $\sigma_{L}$ are the transversely and longitudinally polarized components of the production cross section, as a function of the transverse momentum ($p_{T}^{\Upsilon}$) for the $\Upsilon(1S)$ and $\Upsilon(2S)$. Significant $p_{T}^{\Upsilon}$-dependent longitudinal polarization is observed for the $\Upsilon(1S)$. A comparison with theoretical models is presented.
We report on a search for large extra dimensions in a data sample of approximately 1 fb^{-1} of p pbar collisions at sqrt(s) = 1.96 TeV. We investigate Kaluza-Klein graviton production with a photon ...and missing transverse energy in the final state. At the 95% C.L. we set limits on the fundamental mass scale M_{D} from 884 GeV to 778 GeV for 2 to 8 extra dimensions.
We present a study of four muon, four electron, and two muon two electron events using 1 fb^(-1) of data collected with the D0 detector at the Fermilab Tevatron p-barp Collider at sqrt(s) = 1.96 TeV. ...Requiring the lepton pair masses to be greater than 30 GeV, we observe one event, consistent with the expected background of 0.13 +- 0.03 events and with the predicted standard model ZZ and Z\gamma^* production of 1.71 +-0.15 events. We set an upper limit on the ZZ and Z\gamma^* cross section of 4.4 pb at the 95% C.L. We also derive limits on anomalous neutral trilinear ZZZ and ZZ\gamma^* gauge couplings. The one-parameter 95%$ C.L. coupling limits with a form factor scale Lambda = 1.2 TeV are -0.28 < f_(40)^Z < 0.28, -0.31 < f_(50)^Z < 0.29, -0.26 < f_(40)^\gamma < 0.26, and -0.30 < f_(5 0)^\gamma < 0.28.
We measure the ttbar production cross section in ppbar collisions at sqrt{s}=1.96 TeV in the lepton+jets channel. Two complementary methods discriminate between signal and background, b-tagging and a ...kinematic likelihood discriminant. Based on 0.9 fb-1 of data collected by the D0 detector at the Fermilab Tevatron Collider, we measure sigma_ttbar=7.62+/-0.85 pb, assuming the current world average m_t=172.6 GeV. We compare our cross section measurement with theory predictions to determine a value for the top quark mass of 170+/-7 GeV.
We report a search for R-parity violating production and decay of sneutrino particles in the e+mu final state with 1.04+-0.06 fb-1 of data collected with the D0 detector at the Fermilab Tevatron ...Collider in 2002--2006. Good agreement between the data and the standard model prediction is observed. With no evidence for new physics, we set limits on the R-parity violating couplings $\lambda^{\prime}_{311}$ and $\lambda_{312}$ as a function of sneutrino mass.
We report on a measurement of the inclusive jet cross section in $p \bar{p}$ collisions at a center-of-mass energy $\sqrt s=$1.96 TeV using data collected by the D0 experiment at the Fermilab ...Tevatron Collider corresponding to an integrated luminosity of 0.70 fb$^{-1}$. The data cover jet transverse momenta from 50 GeV to 600 GeV and jet rapidities in the range -2.4 to 2.4. Detailed studies of correlations between systematic uncertainties in transverse momentum and rapidity are presented, and the cross section measurements are found to be in good agreement with next-to-leading order QCD calculations.
In 0.9 fb$^{-1}$ of $p \bar p$ collisions, D0 has observed an excess of events with an isolated lepton, missing transve rse momentum, and two to four jets. This excess is consistent with single top ...quark production. We examine these data to study the Lorentz structure of the $Wtb$ coupling. The standard model predicts a left-handed vector coupling at the $Wt b$ vertex. The most general lowest dimension, CP-conserving Lagrangian admits right-handed vector and left- or right-h anded tensor couplings as well. We find that the data prefer the left-handed vector coupling and set upper limits on the anomalous couplings. These are the first direct constraints on a general $Wtb$ interaction and the first direct limits on left- and right-handed tensor couplings.
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