We present measurements of the differential cross section $d\sigma/dp_{T}^{\gamma}$ for the associated production of a $c$-quark jet and an isolated photon with rapidity $|y^{\gamma}|< 1.0$ and ...transverse momentum $30 < p_{T}^{\gamma} < 300$ GeV. The $c$-quark jets are required to have $|y^{jet}| < 1.5$ and $p_{T}^{jet} >15$ GeV. The cross section ratios $\sigma(\gamma+c)/\sigma(\gamma+b)$ as a function of $p_{T}^{\gamma}$ are also presented. The results are based on data corresponding to an integrated luminosity of 8.7 fb$^{-1}$ recorded with the D0 detector at the Fermilab Tevatron $p\bar{p}$ Collider at $\sqrt{s}=$1.96 TeV. The obtained results are compared to next-to-leading order perturbative QCD calculations using various parton distribution functions, to predictions based on the $k_{T}$-factorization approach, and to predictions from the Sherpa and Pythia Monte Carlo event generators.
We present a measurement of the cross section for $W$ boson production in association with at least one {$b$-quark} jet in proton-antiproton collisions. The measurement is made using data ...corresponding to an integrated luminosity of 6.1\ifb recorded with the D0 detector at the Fermilab Tevatron \ppbar Collider at $\sqrt{s}=1.96$ TeV. We measure an inclusive cross section of {$\sigma(W \sim(\to\mu\nu) + b + X) = 1.04 \pm 0.05\thinspace$(stat.) $\pm 0.12 \thinspace$(syst.) pb} and $\sigma(W (\to e\nu) + b + X) = 1.00$ \pm 0.04 \thinspace$(stat.) $\pm 0.12 \thinspace$(syst.) pb in the phase space defined by $p_T^\nu > 25$ GeV, $p_T^{\text{$b$-jet}}>20$ GeV, $|\eta^{\text{$b$-jet}}|<1.1$, and a muon (electron) with $p_T^\ell>20$ GeV and $|\eta^\mu|<1.7$ ($|\eta^e|<1.1$ or $1.5<|\eta^e|<2.5$). The combined result per lepton family is $\sigma(W (\to \ell \nu) + b + X) = 1.05$ $\pm 0.12 \thinspace$(stat.+syst.) for $|\eta^\ell|<1.7$. The results are in agreement with predictions from next-to-leading order QCD calculations using \textsc{mcfm}, $\sigma(W+b)\cdot {\cal B}(W \to \ell \nu)= 1.34 ^{+0.41}_{-0.34}\thinspace(\textrm{syst.})$, and also with predictions from the \textsc{sherpa} and \textsc{madgraph} Monte Carlo event generators.
We present a search for the standard model (SM) Higgs boson produced in association with a Z boson in 9.7 fb-1 of ppbar collisions collected with the D0 detector at the Fermilab Tevatron Collider at ...sqrt(s) = 1.96 TeV. Selected events contain one reconstructed Z-> e+e- or Z->mu+mu- candidate and at least two jets, including at least one jet from a b quark. Upper limits at the 95% C.L. on the ZH production cross section times branching ratio for H->bbbar are set for Higgs boson masses 90 <= M_H <= 150 GeV. The observed (expected) limit for M_H = 125 GeV is 7.1 (5.1) times the SM cross section. To validate the search procedure, we also measure the cross section for ZZ production in the same final state. It is found to be 0.8 +- 0.4 (stat) +- 0.4 {syst) times its SM prediction, with a significance of 1.5 standard deviations with respect to the background-only hypothesis.
We present a measurement of the ratio of multijet cross sections in p p A= collisions at s = 1.96 TeV at the Fermilab Tevatron Collider. The measurement is based on a data set corresponding to an ...integrated luminosity of 0.7 fb - 1 collected with the D0 detector. The ratio of the inclusive three-jet to two-jet cross sections, R 3 / 2 , has been measured as a function of the jet transverse momenta. The data are compared to QCD predictions in different approximations. Popular tunes of the pythia event generator do not agree with the data, while sherpa provides a reasonable description of the data. A perturbative QCD prediction in next-to-leading order in the strong coupling constant, corrected for non-perturbative effects, gives a good description of the data.
We present final searches of the anomalous gammaWW and ZWW trilinear gauge boson couplings from WW and WZ production using lepton plus dijet final states and a combination with results from Wgamma, ...WW, and WZ production with leptonic final states. The analyzed data correspond to up to 8.6/fb of integrated luminosity collected by the D0 detector in pp-bar collisions at sqrt{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 Delta\kappa_\gamma, lambda, and Delta g_1^Z for a cutoff energy scale Lambda=2 TeV. The combined 68% C.L. limits are -0.057
We present measurements of the differential cross section d I / d p T gamma for the associated production of a c-quark jet and an isolated photon with rapidity | y gamma | 15 GeV . The ratio of ...differential cross sections for gamma + c to gamma + b production as a function of p T gamma is also presented. The results are based on data corresponding to an integrated luminosity of 8.7 fb - 1 recorded with the D0 detector at the Fermilab Tevatron p p A= Collider at s = 1.96 TeV . The obtained results are compared to next-to-leading order perturbative QCD calculations using various parton distribution functions, to predictions based on the k T -factorization approach, and to predictions from the sherpa and pythia Monte Carlo event generators.
We present a search for the standard model Higgs boson in final states with a charged lepton (electron or muon), missing transverse energy, and two or three jets, at least one of which is identified ...as a $b$-quark jet. The search is primarily sensitive to $WH\to\ell\nu b\bar{b}$ production and uses data corresponding to 9.7 fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron $p\bar{p}$ Collider at $\sqrt{s}=1.96$ TeV. We observe agreement between data and the expected background. For a Higgs boson mass of 125 GeV, we set a 95% C.L. upper limit on the production of a standard model Higgs boson of 5.2$\times\sigma_{\rm SM}$, where $\sigma_{\rm SM}$ is the standard model Higgs boson production cross section, while the expected limit is 4.7$\times\sigma_{\rm SM}$.
We present a search for the standard model Higgs boson in 9.5 fb-1 of ppbar collisions at sqrt(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 ppbar->ZH->vvbb production. The search is also sensitive to the WH->lvbb 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 sigma(ppbar->Z/WH), 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 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.
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