We present searches for the anomalous gamma WW and ZWW trilinear gauge boson couplings from WW and WZ production using lepton plus dijet final states and a combination with results from W gamma , WW, ...and WZ production with leptonic final states. The analyzed data correspond to up to 8.6 fb - 1 of integrated luminosity collected by the D0 detector in p p A= collisions at s = 1.96 TeV . We set the most stringent limits at a hadron collider to date assuming two different relations between the anomalous coupling parameters I kappa gamma , I>, and I g 1 Z for a cutoff energy scale I = 2 TeV . The combined 68% C.L. limits are - 0.057 < I kappa gamma < 0.154 , - 0.015 < 0.028 , and - 0.008 < I g 1 Z < 0.054 for the LEP parameterization, and - 0.007 < I kappa < 0.081 and - 0.017 < 0.028 for the equal couplings parameterization. We also present the most stringent limits of the W boson magnetic dipole and electric quadrupole moments.
We present a measurement of the average value of a new observable at hadron colliders that is sensitive to QCD dynamics and to the strong coupling constant, while being only weakly sensitive to ...parton distribution functions. The observable measures the angular correlations of jets and is defined as the number of neighboring jets above a given transverse momentum threshold which accompany a given jet within a given distance IR in the plane of rapidity and azimuthal angle. The ensemble average over all jets in an inclusive jet sample is measured and the results are presented as a function of transverse momentum of the inclusive jets, in different regions of IR and for different transverse momentum requirements for the neighboring jets. The measurement is based on a data set corresponding to an integrated luminosity of 0.7 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider in p p A= collisions at s = 1.96 TeV . The results are well described by a perturbative QCD calculation in next-to-leading order in the strong coupling constant, corrected for non-perturbative effects. From these results, we extract the strong coupling and test the QCD predictions for its running over a range of momentum transfers of 50a400 GeV.
We present the results of a search for the flavor changing neutral current decay inline imageinline image using 6.1 fbsuper-1 of inline imageinline image collisions at inline imageinline image ...collected by the D0 experiment at the Fermilab Tevatron Collider. The observed number of inline imageinline image candidates is consistent with background expectations. The resulting upper limit on the branching fraction is inline imageinline image at the 95% C.L. This limit is a factor of 2.4 better than that of the previous D0 analysis and the best limit to date.
We present a measurement of the differential cross section for inline imageinline image events produced in inline imageinline image collisions at inline imageinline image as a function of the ...transverse momentum (p sub(T) of the top quark. The selected events contain a high-p) sub(T) lepton (l), a large imbalance in p sub(T, four or more jets with at least one candidate for a b jet, and correspond to 1 fbsuper-1 of integrated luminosity recorded with the D0 detector. Objects in the event are associated through a constrained kinematic fit to the inline imageinline image process. Results from next and next-to-next-to-leading-order perturbative QCD calculations agree with the measured differential cross section. Comparisons are also provided to predictions from Monte Carlo event generators using QCD calculations at different levels of precision.)
The inclusive dijet production double differential cross section as a function of the dijet invariant mass and of the largest absolute rapidity of the two jets with the largest transverse momentum in ...an event is measured in inline imageinline image collisions at inline imageinline image using 0.7 fbsuper-1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The measurement is performed in six rapidity regions up to a maximum rapidity of 2.4. Next-to-leading order perturbative QCD predictions are found to be in agreement with the data.
We present a new measurement of the Z/ gamma super* transverse momentum distribution in the range 0-330 GeV, in proton-antiproton collisions at inline imageinline image. The measurement uses 0.97 ...fbsuper-1 of integrated luminosity recorded by the D0 experiment and is the first using the Z/ gamma super=-microsuper+microsuper-+X channel at this center-of-mass energy. This is also the first measurement of the Z/ gamma super* transverse momentum distribution that presents the result at the level of particles entering the detector, minimizing dependence on theoretical models. As any momentum of the Z/ gamma super* in the plane transverse to the incoming beams must be balanced by some recoiling system, primarily the result of QCD radiation in the initial state, this variable is an excellent probe of the underlying process. Tests of the predictions of QCD calculations and current event generators show they have varied success in describing the data. Using this measurement as an input to theoretical predictions will allow for a better description of hadron collider data and hence it will increase experimental sensitivity to rare signals.
We report the results of a search for pair production of scalar bottom quarks (inline imageinline image) and scalar third-generation leptoquarks (LQ sub(3) in 5.2 fbsuper-1 of inline imageinline ...image collisions at the D0 experiment of the Fermilab Tevatron Collider. Scalar bottom quarks are assumed to decay to a neutralino (inline imageinline image) and a b quark, and we set 95% C.L. lower limits on their production in the (inline imageinline image, inline imageinline image) mass plane such as inline imageinline image for inline imageinline image and inline imageinline image for inline imageinline image. The leptoquarks are assumed to decay to a tau neutrino and a b quark, and we set a 95% C.L. lower limit of 247 GeV on the mass of a charge-1/3 third-generation scalar leptoquark.)
We present a search for the standard model Higgs boson in 9.5 fb-1 of p p A= collisions at s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. The final state considered ...contains a pair of b jets and is characterized by an imbalance in transverse energy, as expected from p p A= ? Z H ? ? ? A= b b A= production. The search is also sensitive to the W H ? l ? b b A= channel when the charged lepton is not identified. The data are found to be in good agreement with the expected background. For a Higgs boson mass of 125 GeV, we set a limit at the 95% C.L. on the cross section s (p p A= ? Z / W H) , assuming standard model branching fractions, that is a factor of 4.3 times larger than the theoretical standard model value, while the expected factor is 3.9. The search is also used to measure a combined WZ and ZZ production cross section that is a factor of 0.94 +/- 0.31 (stat) +/- 0.34 (syst) times the standard model prediction of 4.4 pb, with an observed significance of 2.0 standard deviations.
We report results from searches for neutral Higgs bosons produced in p{bar p} collisions recorded by the D0 experiment at the Fermilab Tevatron Collider. We study the production of inclusive neutral ...Higgs boson in the {tau}{tau} final state and in association with a b quark in the b{tau}{tau} and bbb final states. These results are combined to improve the sensitivity to the production of neutral Higgs bosons in the context of the minimal supersymmetric standard model (MSSM). The data are found to be consistent with expectation from background processes. Upper limits on MSSM Higgs boson production are set for Higgs boson masses ranging from 90 to 300 GeV. We exclude tan {beta} > 20-30 for Higgs boson masses below 180 GeV. These are the most stringent constraints on MSSM Higgs boson production in p{bar p} collisions.
We present the first direct search for single top quark production using reconstructed tau leptons in the final state. The search is based on 4.8 fbsuper-1 of integrated luminosity collected in ...inline imageinline image collisions at inline imageinline image with the D0 detector at the Fermilab Tevatron Collider. We select events with a final state including an isolated tau lepton, missing transverse energy, two or three jets, one or two of them being identified as b quark jet. We use a multivariate technique to discriminate signal from background. The number of events observed in data in this final state is consistent with the signal plus background expectation. We set in the tau + jets channel an upper limit on the single top quark cross section of 7.3 pb at the 95% C.L. This measurement allows a gain of 4% in expected sensitivity for the observation of single top production when combining it with electron + jets and muon + jets channels already published by the D0 Collaboration with 2.3 fbsuper-1 of data. We measure a combined cross section of 3.84super+0.89 sub(-0.83 pb, which is the most precise measurement to date.)
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