Wy Production and Limits on Anomalous WWy Couplings in pp̅ Collisions √s = 1.96 TeV

We measure the cross section and the difference in rapidities between photons and charged leptons for inclusive W(→ lv) + y production in ey and µy final states. Using data corresponding to an integrated luminosity of 4.2 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider, the measured cross section times branching fraction for the process pp̅ → Wy + X → lvy + X and the distribution of the charge-signed photon-lepton rapidity difference are found to be in agreement with the standard model. These results provide the most stringent limits on anomalous WW[1] couplings for data from hadron colliders: -0.4 \u3c ∆ky \u3c 0.4 and -0.08 \u3c λy \u3c 0.07 at the 95% C.L

Evidence for Simultaneous Production of J/ψ and ϒ Mesons

We report evidence for the simultaneous production of J/ψ and ϒ mesons in 8.1 fb−1 of data collected at √s = 1.96 TeV by the D0 experiment at the Fermilab p¯p Tevatron Collider. Events with these characteristics are expected to be produced predominantly by gluon-gluon interactions. In this analysis, we extract the effective cross section characterizing the initial parton spatial distribution, σeff = 2.2 ± 0.7(stat) ± 0.9(syst) mb

Wy Production and Limits on Anomalous WWy Couplings in pp̅ Collisions √s = 1.96 TeV

We measure the cross section and the difference in rapidities between photons and charged leptons for inclusive W(→ lv) + y production in ey and µy final states. Using data corresponding to an integrated luminosity of 4.2 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider, the measured cross section times branching fraction for the process pp̅ → Wy + X → lvy + X and the distribution of the charge-signed photon-lepton rapidity difference are found to be in agreement with the standard model. These results provide the most stringent limits on anomalous WW[1] couplings for data from hadron colliders: -0.4 \u3c ∆ky \u3c 0.4 and -0.08 \u3c λy \u3c 0.07 at the 95% C.L

[?] lifetime measurement in the \u3ci\u3eCP\u3c/i\u3e-odd decay channel [?] → J/ψ f\u3ci\u3e0\u3c/i\u3e(980)

The lifetime of the [?] meson is measured in the decay channel [?] → J/ψπ+π− with 880 ≤ Mπ+π- - ≤ 1080 MeV / c2, which is mainly a CP-odd state and dominated by the f0 (980) resonance. In 10.4 fb-1 of data collected with the D0 detector in Run II of the Tevatron, the lifetime of the [?] meson is measured to be [?] = 1.70 ± 0.14(stat) ± 0.05(syst) ps. Neglecting CP violation in [?]/[?] mixing, the measurement can be translated into the width of the heavy mass eigenstate of the [?], ΓH = 0.59 ± 0.05(stat) ± 0.02(syst) ps-1

Measurement of the top quark mass using the matrix element technique in dilepton final states

We present a measurement of the top quark mass in pp collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. The data were collected by the D0 experiment corresponding to an integrated luminosity of 9.7 fb−1. The matrix element technique is applied to tt events in the final state containing leptons (electrons or muons) with high transverse momenta and at least two jets. The calibration of the jet energy scale determined in the lepton + jets final state of tt decays is applied to jet energies. This correction provides a substantial reduction in systematic uncertainties. We obtain a top quark mass of mt = 173.93 ± 1.84 GeV

Search for a Fermiophobic and Standard Model Higgs Boson in Diphoton Final States

We present a search for the standard model Higgs boson and a fermiophobic Higgs boson in the diphoton final states based on 8.2 fb-1 of pp̅ collisions at √s= 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. No excess of data above background predictions is observed and upper limits at the 95% C.L. on the cross section multiplied by the branching fraction are set which are the most restrictive to date. A fermiophobic Higgs boson with a mass below 112.9 GeV is excluded at the 95% C.L

Direct measurement of the mass difference between top and antitop quarks

We present a direct measurement of the mass difference between top and antitop quarks (∆m) in lepton + jets tt final states using the ‘‘matrix element’’ method. The purity of the lepton + jets sample is enhanced for tt events by identifying at least one of the jets as originating from a b quark. The analyzed data correspond to 3.6 fb-1 of pp collisions at √s = 1.96 TeV acquired by D0 in Run II of the Fermilab Tevatron Collider. The combination of the e + jets and µ + jets channels yields ∆m =0.8 ± 1,8 stat ± 0.5(syst) GeV, which is in agreement with the standard model expectation of no mass difference

Search for associated Higgs boson production using like charge dilepton events in pp̅ collisions at √s= 1.96 TeV

We present a search for associated Higgs boson production in the process pp̅ → W / ZH → l±l± + X in ee, eµ, and µµ final states. The search is based on data collected by the D0 experiment at the Fermilab Tevatron Collider at √s = 1.96 TeV corresponding to 5.3 fb-1 of integrated luminosity. We require two isolated leptons (electrons or muons) with the same electric charge and additional kinematic requirements. No significant excess above background is observed, and we set 95% C.L. observed (expected) upper limits on ratio of the production cross section to the standard model prediction of 6.4 (7.3) for a Higgs boson mass of 165 GeV and 13.5 (19.8) for a mass of 115 GeV

Measurement of the forward-backward asymmetries in the production of Ξ and Ω baryons in \u3ci\u3epp\u3c/i\u3e collisions

We measure the forward-backward asymmetries AFB of charged Ξ and Ω baryons produced in pp collisions recorded by the D0 detector at the Fermilab Tevatron collider at [?] = 1.96 TeV as a function of the baryon rapidity y. We find that the asymmetries AFB for charged Ξ and Ω baryons are consistent with zero within statistical uncertainties

Measurement of the inclusive \u3ci\u3ett\u3c/i\u3e production cross section in \u3ci\u3epp\u3c/i\u3e collisions at [?] = 1.96 TeV and determination of the top quark pole mass

The inclusive cross section of top quark-antiquark pairs produced in pp collisions at [?] = 1.96 TeV is measured in the lepton + jets and dilepton decay channels. The data sample corresponds to 9.7 fb−1 of integrated luminosity recorded with the D0 detector during Run II of the Fermilab Tevatron Collider. Employing multivariate analysis techniques we measure the cross section in the two decay channels and we perform a combined cross section measurement. For a top quark mass of 172.5 GeV, we measure a combined inclusive top quark-antiquark pair production cross section of σtt = 7.26 ± 0.13(stat)[?] (syst) pb which is consistent with standard model predictions. We also perform a likelihood fit to the measured and predicted top quark mass dependence of the inclusive cross section, which yields a measurement of the pole mass of the top quark. The extracted value is mt = 172.8 ± 1.1(theo)[?] (exp) GeV