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

Studies of X(3872) and ψ(2S) production in p\bar{p}over-bar collisions at 1.96 TeV

We present various properties of the production of the X (3872) and ψ(2S) states based on 10.4fb‾¹ collected by the D0 experiment in Tevatron p\bar{p} collisions at \sqrt{s} = 1.96 TeV. For both states, we measure the nonprompt fraction fNP of the inclusive production rate due to decays of b-flavored hadrons. We find the fNP values systematically below those obtained at the LHC. The fNP fraction for ψ(2S) increases with transverse momentum, whereas for the X(3872) it is constant within large uncertainties, in agreement with the LHC results. The ratio of prompt to nonprompt ψ(2S) production, (1 - fNP)/fNP, decreases only slightly going from the Tevatron to the LHC, but for the X(3872), this ratio decreases by a factor of about 3. We test the soft-pion signature of the X(3872) modeled as a weakly bound charm-meson pair by studying the production of the X(3872) as a function of the kinetic energy of the X(3872) and the pion in the X(3872) π center-of-mass frame. For a subsample consistent with prompt production, the results are incompatible with a strong enhancement in the production of the X(3872) at the small kinetic energy of the X(3872) and the π in the X(3872)π center-of-mass frame expected for the X + soft-pion production mechanism. For events consistent with being due to decays of hadrons, there is no significant evidence for the soft-pion effect, but its presence at the level expected for the binding energy of 0.17 MeV and the momentum scale Λ = M(π) is not ruled out

Properties of Z±c(3900) produced in pp¯ collisions

We study the production of the exotic charged charmoniumlike state Z ± c ( 3900 ) in p ¯ p collisions through the sequential process ψ ( 4260 ) → Z ± c ( 3900 ) π ∓ , Z ± c ( 3900 ) → J / ψ π ± . Using the subsample of candidates originating from semi-inclusive weak decays of b -flavored hadrons, we measure the invariant mass and natural width to be M = 3902.6 + 5.2 − 5.0 ( stat ) + 3.3 − 1.4 ( syst )     MeV and Γ = 3 2 + 28 − 21 ( stat ) + 26 − 7 ( syst )     MeV , respectively. We search for prompt production of the Z ± c ( 3900 ) through the same sequential process. No significant signal is observed, and we set an upper limit of 0.70 at the 95% credibility level on the ratio of prompt production to the production via b -hadron decays. The study is based on 10.4     f b − 1 of p ¯ p collision data collected by the D0 experiment at the Fermilab Tevatron collider

Combined Tevatron upper limit on gg->H->W+W- and constraints on the Higgs boson mass in fourth-generation fermion models

Report number: FERMILAB-PUB-10-125-EWe combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process gg->H->W+W- in p=pbar collisions at the Fermilab Tevatron Collider at sqrt{s}=1.96 TeV. With 4.8 fb-1 of integrated luminosity analyzed at CDF and 5.4 fb-1 at D0, the 95% Confidence Level upper limit on \sigma(gg->H) x B(H->W+W-) is 1.75 pb at m_H=120 GeV, 0.38 pb at m_H=165 GeV, and 0.83 pb at m_H=200 GeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% Confidence Level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.We combine results from searches by the CDF and D0 collaborations for a standard model Higgs boson (H) in the process gg→H→W+W- in pp̅ collisions at the Fermilab Tevatron Collider at √s=1.96  TeV. With 4.8  fb-1 of integrated luminosity analyzed at CDF and 5.4  fb-1 at D0, the 95% confidence level upper limit on σ(gg→H)×B(H→W+W-) is 1.75 pb at mH=120  GeV, 0.38 pb at mH=165  GeV, and 0.83 pb at mH=200  GeV. Assuming the presence of a fourth sequential generation of fermions with large masses, we exclude at the 95% confidence level a standard-model-like Higgs boson with a mass between 131 and 204 GeV.Peer reviewe

Combination of D0 measurements of the top quark mass

We present a combination of measurements of the top quark mass by the D0 experiment in the lepton+jets and dilepton channels. We use all the data collected in Run I (1992–1996) at √s=1.8  TeV and Run II (2001–2011) at √s=1.96  TeV of the Tevatron p¯p collider, corresponding to integrated luminosities of 0.1  fb−1 and 9.7  fb−1, respectively. The combined result is: mt=174.95±0.40(stat)±0.64(syst)  GeV=174.95±0.75  GeV

Measurement of angular correlations of jets at root s=1.96 TeV and determination of the strong coupling at high momentum transfers

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 �R 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 �R 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 collisions at √ s = 1.96 TeV. The results are well described by a perturbative QCD calculation in next-toleading 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 50–400 GeV

Search for violation of CPT and Lorentz invariance in B-s(0) Meson oscillations

We present the first search for CPT-violating effects in the mixing of B0s mesons using the full Run II data set with an integrated luminosity of 10.4  fb−1 of proton-antiproton collisions collected using the D0 detector at the Fermilab Tevatron Collider. We measure the CPT-violating asymmetry in the decay B0s→μ±D±s as a function of celestial direction and sidereal phase. We find no evidence for CPT-violating effects and place limits on the direction and magnitude of flavor-dependent CPT- and Lorentz-invariance violating coupling coefficients. We find 95% confidence intervals of Δa⊥<1.2×10−12  GeV and (−0.8<ΔaT−0.396ΔaZ<3.9)×10−13  GeV