We present the first measurements of the differential cross section $d\sigma/dp_{T}^{\gamma}$ for the production of an isolated photon in association with at least two $b$-quark jets. The ...measurements consider photons with rapidities $|y^\gamma| < 1.0$ and transverse momenta $30 < p_{T}^{\gamma} < 200$~\GeV. The $b$-quark jets are required to have $p_T^{jet}>15$ GeV and $| y^{jet}| < 1.5$. The ratio of differential production cross sections for $\gamma+2~b$-jets to $\gamma+b$-jet as a function of $p_{T}^{\gamma}$ is also presented. The results are based on the proton-antiproton collision data at $\sqrt{s}=$1.96~\TeV collected with the D0 detector at the Fermilab Tevatron Collider. The measured cross sections and their ratios are compared to the next-to-leading order perturbative QCD calculations as well as predictions based on the $k_{T}$-factorization approach and those from the SHERPA and PYTHIA Monte Carlo event generators.
We present a measurement of the cross sections for the associated production of a W boson with at least one heavy quark jet, b or c, in proton–antiproton collisions. Data corresponding to an ...integrated luminosity of 8.7 fb−1 recorded with the D0 detector at the Fermilab Tevatron pp¯ Collider at s=1.96 TeV are used to measure the cross sections differentially as a function of the jet transverse momenta in the range 20 to 150 GeV. These results are compared to calculations of perturbative QCD theory as well as predictions from Monte Carlo generators.
We present a measurement of the direct CP-violating charge asymmetry in B^+- mesons decaying to J/psi K^+- and J/psi pi^+- where J/psi decays to mu^+ mu^-, using 10.4 fb^-1 of proton-antiproton ...collisions collected by the D0 detector during Run II at the Fermilab Tevatron Collider. A difference in the yield of B^- and B^+ mesons in these decays is found by fitting to the difference between their reconstructed invariant mass distributions resulting in asymmetries of ajpk = 0.59 +/- 0.36 %, which is the most precise measurement to date, and ajppi = -4.2 +/- 4.8 %. Both measurements are consistent with standard model predictions.
We present a measurement of the time-integrated flavor-specific semileptonic charge asymmetry in the decays of Bs mesons that have undergone flavor mixing, a^s_ls, using B_s^0 (barB_s^0) -> D_s^-/+ ...mu^+/- X decays, with D_s^-/+ -> phi pi^-/+ and phi K^+ K^-, using 10.4 fb^-1 of proton-antiproton collisions collected by the D0 detector during Run II at the Fermilab Tevatron Collider. A fit to the difference between the time-integrated D_s^-$ and D_s^+ mass distributions of the B_s^0 and barB^0_s candidates yields the flavor-specific asymmetry a^s_ls = -1.08 pm 0.72 (stat) +/-0.17 (syst)% which is the most precise measurement and in agreement with the standard model prediction.
We present measurements of the cross sections for the two main production modes of single top quarks in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$\;TeV in the Run II data collected with the D0 ...detector at the Fermilab Tevatron Collider, corresponding to an integrated luminosity of 9.7\;fb$^{-1}$. The s-channel cross section is measured to be $\sigma({\ppbar}{\rargap}tb+X) = 1.10^{+0.33}_{-0.31}$\;pb with no assumptions on the value of the t-channel cross section. Similarly, the t-channel cross section is measured to be $\sigma({\ppbar}{\rargap}tqb+X) = 3.07^{+0.54}_{-0.49}$\;pb. We also measure the $s+t$ combined cross section as $\sigma({\ppbar}{\rargap}tb+X, tqb+X) = 4.11^{+0.60}_{-0.55}$\;pb and set a lower limit on the CKM matrix element $|V_{tb}| > 0.92 at 95% C.L., assuming $m_t=172.5$\;GeV. The probability to measure a cross section for the s channel at the observed value or higher in the absence of signal is $1.0\times 10^{-4}$, corresponding to a significance of 3.7 standard deviations.
We present a measurement of the ratio of multijet cross sections in pp-bar collisions at sqrt(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, R3/2, 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 the first measurements of the differential cross section dσ/dpTγ for the production of an isolated photon in association with at least two b-quark jets. The measurements consider photons ...with rapidities |yγ|<1.0 and transverse momenta 30<pTγ<200 GeV. The b-quark jets are required to have pTjet>15 GeV and |yjet|<1.5. The ratio of differential production cross sections for γ+2b-jets to γ+b-jet as a function of pTγ is also presented. The results are based on the proton–antiproton collision data at s=1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. The measured cross sections and their ratios are compared to the next-to-leading order perturbative QCD calculations as well as predictions based on the kT-factorization approach and those from the sherpa and pythia Monte Carlo event generators.
We present the first combined measurement of the rapidity and transverse momentum dependence of dijet azimuthal decorrelations, based on the recently proposed quantity $R_{\Delta \phi}$. The variable ...$R_{\Delta \phi}$ measures the fraction of the inclusive dijet events in which the azimuthal separation of the two jets with the highest transverse momenta is less than a specified value for the parameter $\Delta \phi_{\rm max}$. The quantity $R_{\Delta \phi}$ is measured in $p\bar{p}$ collisions at $\sqrt{s}=1.96\,$TeV, as a function of the dijet rapidity interval, the total scalar transverse momentum, and $\Delta \phi_{\rm max}$. The measurement uses an event sample corresponding to an integrated luminosity of $0.7\,$fb$^{-1}$ collected with the D0 detector at the Fermilab Tevatron Collider. The results are compared to predictions of a perturbative QCD calculation at next-to-leading order in the strong coupling with corrections for non-perturbative effects. The theory predictions describe the data, except in the kinematic region of large dijet rapidity intervals and large $\Delta \phi_{\rm max}$.
We present measurements of direct photon pair production cross sections using 8.5 fb$^{-1}$ of data collected with the D0 detector at the Fermilab Tevatron $p \bar p$ collider. The results are ...presented as differential distributions of the photon pair invariant mass $d\sigma/dM_{\gamma \gamma}$, pair transverse momentum $d \sigma /dp^{\gamma \gamma}_T$, azimuthal angle between the photons $d\sigma/d\Delta \phi_{\gamma \gamma}$, and polar scattering angle in the Collins-Soper frame $d\sigma /d|\cos \theta^*|$. Measurements are performed for isolated photons with transverse momenta $p^{\gamma}_T>18 ~(17)$ GeV for the leading (next-to-leading) photon in $p_T$, pseudorapidities $|\eta^{\gamma}|<0.9$, and a separation in $\eta-\phi$ space $\Delta\mathcal R_{\gamma\gamma} > 0.4$. We present comparisons with the predictions from Monte Carlo event generators {\sc diphox} and {\sc resbos} implementing QCD calculations at next-to-leading order, $2\gamma${\sc nnlo} at next-to-next-to-leading order, and {\sc sherpa} using matrix elements with higher-order real emissions matched to parton shower.
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.
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