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Träfflista för sökning "WFRF:(Shivpuri K) srt2:(2013)"

Sökning: WFRF:(Shivpuri K) > (2013)

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1.
  • Abazov, V. M., et al. (författare)
  • Measurement of leptonic asymmetries and top-quark polarization in t(t)over-bar production
  • 2013
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 87:1, s. 011103-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present measurements of lepton (l) angular distributions in top-quark (t) pair production and t (t) over bar -> W(+)bW-(b) over bar -> l(+) vbl-(v) over bar(b) over bar decays produced in p (p) over bar collisions at a center-of-mass energy of root s = 1.96 TeV, where l is an electron or muon. Using data corresponding to an integrated luminosity of 5.4 fb(-1), collected with the D0 detector at the Fermilab Tevatron Collider, we measure for the first time the leptonic forward-backward asymmetry in dilepton final states and obtain A(FB)(l) = (5.8 +/- 5.1(stat) +/- 1.3(syst))%, corrected for detector acceptance. This is compared to the standard model prediction of A(FB)(l)(predicted) = (4.7 +/- 0.1)%. A deviation from the standard model prediction as previously seen in a D0 measurement based on the analysis of the l + jets final state is not observed in these dilepton final states. The two results differ from each other by 1.4 standard deviations and are combined to obtain A(FB)(l) = (11.8 +/- 3.2)%. Furthermore, we present a first study of the top-quark polarization.
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2.
  • Abazov, V. M., et al. (författare)
  • Measurement of the Semileptonic Charge Asymmetry using B-S(0) -> D-s mu X Decays
  • 2013
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 110:1, s. 011801-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a measurement of the time-integrated flavor-specific semileptonic charge asymmetry in the decays of B-s(0) mesons that have undergone flavor mixing, a(sl)(s), using B-s(0)((B) over bar (0)(s)) -> 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 D0 detector during Run II at the Fermilab Tevatron Colllider. A fit to the difference between the time-integrated D-s(-) and D-s(+) mass distributions of the B-s(0) and ($) over bar (0)(s) candidates yields the flavor-specific asymmetry a(sl)(s) = [-1.12 +/- 0.74(stat) +/- 0.17(syst)]%, which is the most precise measurement and in agreement with the standard model prediction.
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3.
  • Abazov, V. M., et al. (författare)
  • Measurement of the differential gamma plus c-jet cross section and the ratio of differential gamma plus c and gamma plus b cross sections in p(p)over-bar collisions at root s=1.96 TeV
  • 2013
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 719:4-5, s. 354-361
  • Tidskriftsartikel (refereegranskat)abstract
    • 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 vertical bar y(gamma)vertical bar < 1.0 and transverse momentum 30 < p(T)(gamma) < 300 GeV. The c-quark jets are required to have vertical bar y(jet)vertical bar < 1.5 and p(T)(jet) > 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) over bar Collider at root 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. 
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4.
  • Abazov, V. M., et al. (författare)
  • Measurement of the combined rapidity and p(T) dependence of dijet azimuthal decorrelations in p(p)over-bar collisions at root s=1.96 TeV
  • 2013
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 721:4-5, s. 212-219
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the first combined measurement of the rapidity and transverse momentum dependence of dijet azimuthal decorrelations, using 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 of the parameter Delta phi(max). The quantity R-Delta phi is measured in p (p) over bar collisions at root s = 1.96 TeV, as a function of the dijet rapidity interval, the total scalar transverse momentum, and Delta phi(max). The measurement uses an event sample corresponding to an integrated luminosity of 0.7 fb(-1) collected with the DO 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 well, except in the kinematic region of large dijet rapidity intervals and small Delta phi(max).
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5.
  • Abazov, V. M., et al. (författare)
  • Measurement of the p(p)over-bar -> W plus b plus X production cross section at root s=1.96 TeV D0 Collaboration
  • 2013
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 718:4-5, s. 1314-1320
  • Tidskriftsartikel (refereegranskat)abstract
    • 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 6.1fb-1 recorded with the D0 detector at the Fermilab Tevatron pp̄ Collider at s=1.96TeV. We measure an inclusive cross section of σ(W(→μν)+b+X)=1.04±0.05(stat.)±0.12(syst.) pb and σ(W(→eν)+b+X)=1.00±0.04(stat.)±0.12(syst.) pb in the phase space defined by pTν>25GeV, pTb-jet>20 GeV, |ηb-jet|<1.1, and a muon (electron) with pTℓ>20 GeV and |ημ|<1.7 (|ηe|<1.1 or 1.5<|ηe|<2.5). The combined result per lepton family is σ(W(→ℓν)+b+X)=1.05±0.12(stat.+syst.) pb for |ηℓ|<1.7. The results are in agreement with predictions from next-to-leading order QCD calculations using mcfm, σ(W+b){dot operator}B(W→ℓν)=1.34-0.34+0.41(syst.) pb, and also with predictions from the sherpa and madgraph Monte Carlo event generators.
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6.
  • Abazov, V. M., et al. (författare)
  • Measurement of the ratio of three-jet to two-jet cross sections in p(p)over-bar collisions at root s=1.96 TeV
  • 2013
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 720:1-3, s. 6-12
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a measurement of the ratio of multijet cross sections in p (p) over barp collisions at root 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 DO 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 PYriiiA 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.
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7.
  • Abazov, V. M., et al. (författare)
  • Measurement of the ratio of differential cross sections sigma(p(p)over-bar -> Z + b jet)/sigma(p(p)over-bar -> Z + jet) in p(p)over-bar collisions at root s = 1.96 TeV
  • 2013
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 87:9, s. 092010-
  • Tidskriftsartikel (refereegranskat)abstract
    • We measure the ratio of cross sections, sigma(p (p) over bar -> Z + b jet)/sigma(p (p) over bar -> Z + jet), for associated production of a Z boson with at least one jet. The ratio is also measured as a function of the Z boson transverse momentum, jet transverse momentum, jet pseudorapidity, and the azimuthal angle between the Z boson with respect to the highest p(T) b tagged jet. These measurements use data collected by the D0 experiment in Run II of Fermilab's Tevatron p (p) over bar Collider at a center-of-mass energy of 1.96 TeV, and correspond to an integrated luminosity of 9.7 fb(-1). The results are compared to predictions from next-to-leading order calculations and various Monte Carlo event generators.
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8.
  • Abazov, V. M., et al. (författare)
  • Search for charged massive long-lived particles at root s=1.96 TeV
  • 2013
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 87:5, s. 052011-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a search for charged massive long-lived particles (CMLLPs) that are pair produced in p (p) over bar collisions at root s = 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron collider. Our result is a combination of two searches where either one or both CMLLPs are reconstructed in the detector. We select events with muonlike particles that have both speed and ionization energy loss (dE/dx) different from muons produced in p (p) over bar collisions. In the absence of evidence for CMLLPs corresponding to 6.3 fb(-1) of integrated luminosity, we set limits on the CMLLP masses in several supersymmetric models, excluding masses below 278 GeV for long-lived gaugino-like charginos, and masses below 244 GeV for long-lived Higgsino-like charginos at the 95% C.L. We also set limits on the cross section for pair production of long-lived scalar tau leptons that range from 0.04 to 0.008 pb for scalar tau lepton masses of 100-300 GeV.
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9.
  • Abazov, V. M., et al. (författare)
  • Search for Higgs boson production in oppositely charged dilepton and missing energy final states in 9.7 fb(-1) of p(p)over-bar collisions at root s=1.96 TeV
  • 2013
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:5, s. 052006-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a search for the Higgs boson in final states with two oppositely charged leptons and large missing transverse energy as expected in H -> WW -> lvl(1)v(1)decays. The events are selected from the full Run II data sample of 9.7 fb(-1) of p (p) over bar collisions collected with the D0 detector at the Fermilab Tevatron Collider at root s = 1.96 TeV. To validate our search methodology, we measure the nonresonant WW production cross section and find sigma(WW) 11.6 +/- 0.7 pb, in agreement with the standard model prediction. In the Higgs boson search, no significant excess above the background expectation is observed. Upper limits at the 95% confidence level on the Higgs boson production cross section are therefore derived. Within the standard model, the Higgs boson mass range 159 < M-H < 176 GeV is excluded while the expected exclusion sensitivity is 156 < M-H < 172 GeV. For a mass hypothesis of M-H = 125 GeV, we exclude Higgs boson production cross sections 4.1 times larger than the standard model expectation, which is compatible with the presence of a Higgs boson at this mass. Within a theoretical framework with a fourth generation of fermions, the mass range 125 < M-H < 218 GeV is excluded. The search results are also interpreted in the context of fermiophobic Higgs boson couplings, which yields an exclusion of fermiophobic Higgs boson production cross sections 3.1 times larger than the expectation for M-H = 125 GeV.
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10.
  • Abazov, V. M., et al. (författare)
  • Search for the Higgs boson in lepton, tau, and jets final states
  • 2013
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:5, s. 052005-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a search for the standard model Higgs boson in final states with an electron or muon and a hadronically decaying tau lepton in association with two or more jets using 9:7 fb(-1) of Run II Fermilab Tevatron Collider data collected with the D0 detector. The analysis is sensitive to Higgs boson production via gluon fusion, associated vector boson production, and vector boson fusion, followed by the Higgs boson decay to tau lepton pairs or to W boson pairs. The ratios of 95% C.L. upper limits on the cross section times branching ratio to those predicted by the standard model are obtained for orthogonal subsamples that are enriched in either H -> tau tau decays or H -> WW decays, and for the combination of these subsample limits. The observed and expected limit ratios for the combined subsamples at a Higgs boson mass of 125 GeV are 11.3 and 9.0, respectively.
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  • Resultat 1-10 av 18

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