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  • 451.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Dark Photons from Supersymmetric Hidden Valleys2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 103, p. 081802-Article in journal (Refereed)
  • 452.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Diphoton Events with Large Missing Transverse Energy in 6.3 fb$^{-1}$ of $p\bar{p}$ Collisions at $\sqrt{s} = 1.96$ TeV2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 105, p. 221802-Article in journal (Refereed)
    Abstract [en]

    We report a search for diphoton events with large missing transverse energy produced in pp̅ collisions at √s=1.96  TeV. The data were collected with the D0 detector at the Fermilab Tevatron Collider and correspond to 6.3  fb-1 of integrated luminosity. The observed missing transverse energy distribution is well described by the standard model prediction, and 95% C.L. limits are derived on two realizations of theories beyond the standard model. In a gauge-mediated supersymmetry breaking scenario, the breaking scale Λ is excluded for Λ<124  TeV. In a universal extra dimension model including gravitational decays, the compactification radius Rc is excluded for Rc-1<477  GeV

  • 453.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for First Generation Leptoquark Pair Production in the Electron + Missing Energy + Jets Final State2011In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 84, no 7, p. 071104-Article in journal (Refereed)
    Abstract [en]

    We present a search for the pair production of first generation scalar leptoquarks (LQ) in data corresponding to an integrated luminosity of 5.4 fb(-1) collected with the D0 detector at the Fermilab Tevatron Collider in p (p) over bar collisions at root s = 1.96 TeV. In the channel LQLQ -> eqv(e)q', where q, q' are u or d quarks, no significant excess of data over background is observed, and we set a 95% C. L. lower limit of 326 GeV on the LQ mass, assuming equal probabilities of LQ decays to eq and v(e)q'.

  • 454.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Flavor Changing Neutral Currents in Decays of Top Quarks2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 701, no 3, p. 313-320Article in journal (Refereed)
    Abstract [en]

    We present a search for flavor changing neutral currents in decays of top quarks. The analysis is based on a search for (,=e,μ) final states using 4.1 fb−1 of integrated luminosity of collisions at . We extract limits on the branching ratio B(tZq) (q=u,c quarks), assuming anomalous tuZ or tcZ couplings. We do not observe any sign of such anomalous coupling and set a limit of B<3.2% at 95% C.L.

  • 455.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for flavor changing neutral currents via quark–gluon couplings in single top quark production using 2.3 fb−1 of collisions2010In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 693, no 2, p. 81-87Article in journal (Refereed)
    Abstract [en]

    We present a search for flavor changing neutral currents via quark–gluon couplings in a sample of single top quark final states corresponding to 2.3 fb−1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. We select events containing a single top quark candidates with an additional jet, and obtain separation between signal and background using Bayesian neural networks. We find consistency between background expectation and observed data, and set limits on flavor changing neutral current gluon couplings of the top quark to up quarks (tgu) and charm quarks (tgc). The cross section limits at the 95% C.L. are σtgu<0.20 pb and σtgc<0.27 pb. These correspond to limits on the top quark decay branching fractions of B(tgu)<2.0×10−4 and B(tgc)<3.9×10−3.

  • 456.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Higgs Boson Production in Dilepton and Missing Energy Final States with 5.4 fb$^{-1}$ of $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 104, no 6, p. 061804-Article in journal (Refereed)
    Abstract [en]

    A search for the standard model Higgs boson is presented using events with two charged leptons and large missing transverse energy selected from 5.4  fb-1 of integrated luminosity in pp̅ collisions at √s=1.96  TeV collected with the D0 detector at the Fermilab Tevatron collider. No significant excess of events above background predictions is found, and observed (expected) upper limits at 95% confidence level on the rate of Higgs boson production are derived that are a factor of 1.55 (1.36) above the predicted standard model cross section at mH=165  GeV.

  • 457.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Higgs bosons of the minimal supersymmetric standard model in p(p)over-bar collisions at root s=1.96 TeV D0 Collaboration2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 710, no 4-5, p. 569-577Article in journal (Refereed)
    Abstract [en]

    We report results from searches for neutral Higgs bosons produced in p (p) over bar collisions recorded by the D0 experiment at the Fermilab Tevatron Collider. We study the production of inclusive neutral Higgs boson in the tau tau final state and in association with a b quark in the b tau tau and bbb final states. These results are combined to improve the sensitivity to the production of neutral Higgs bosons in the context of the minimal supersymmetric standard model (MSSM). The data are found to be consistent with expectation from background processes. Upper limits on MSSM Higgs boson production are set for Higgs boson masses ranging from 90 to 300 GeV. We exclude tan beta > 20-30 for Higgs boson masses below 180 GeV. These are the most stringent constraints on MSSM Higgs boson production in p (p) over bar collisions.

  • 458.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Neutral Higgs Bosons in the Multi-b-jet Topology in 5.2fb$^{-1}$ of $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 698, no 2, p. 97-104Article in journal (Refereed)
    Abstract [en]

    Data recorded by the D0 experiment at the Fermilab Tevatron Collider are analyzed to search for neutral Higgs bosons produced in association with b quarks. The search is performed in the three-b-quark channel using multijet-triggered events corresponding to an integrated luminosity of 5.2 fb−1. In the absence of any significant excess above background, limits are set on the cross section multiplied by the branching ratio in the Higgs boson mass range 90 to 300 GeV, extending the excluded regions in the parameter space of the minimal supersymmetric standard model.

  • 459.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Neutral Minimal Supersymmetric Standard Model Higgs Bosons Decaying to Tau Pairs Produced in Association with b Quarks in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV2011In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 107, no 12, p. 121801-Article in journal (Refereed)
    Abstract [en]

    We report results from a search for neutral Higgs bosons produced in association with b quarks using data recorded by the D0 experiment at the Fermilab Tevatron Collider and corresponding to an integrated luminosity of 7.3 fb(-1). This production mode can be enhanced in several extensions of the standard model (SM) such as in its minimal supersymmetric extension (MSSM) at high tan beta. We search for Higgs bosons decaying to tau pairs with one tau decaying to a muon and neutrinos and the other to hadrons. The data are found to be consistent with SM expectations, and we set upper limits on the cross section times branching ratio in the Higgs boson mass range from 90 to 320 GeV/c(2). We interpret our result in the MSSM parameter space, excluding tan beta values down to 25 for Higgs boson masses below 170 GeV/c(2).

  • 460.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for New Fermions ('Quirks') at the Fermilab Tevatron Collider2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 105, p. 211803-Article in journal (Refereed)
    Abstract [en]

    We report results of a search for particles with anomalously high ionization in events with a high transverse energy jet and large missing transverse energy in 2.4  fb-1 of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron pp̅ collider. Production of such particles (quirks) is expected in scenarios with extra QCD-like SU(N) sectors, and this study is the first dedicated search for such signatures. We find no evidence of a signal and set a lower mass limit of 107, 119, and 133 GeV for the mass of a charged quirk with strong dynamics scale Λ in the range from 10 keV to 1 MeV and N=2, 3, and 5, respectively.

  • 461.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Next-to-Minimal Supersymmetric Higgs Bosons in the $h\to aa\to\mu\mu \mu\mu$, $\mu\mu \tau\tau$ Channels Using $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 103, p. 061801-Article in journal (Refereed)
  • 462.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Pair Production of First-Generation Leptoquarks in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV}2009In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 681, p. 224-232Article in journal (Refereed)
  • 463.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for pair production of the scalar top quark in muon plus tau final states D0 Collaboration2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 710, no 4-5, p. 578-586Article in journal (Refereed)
    Abstract [en]

    We present a search for the pair production of scalar top quarks ((t) over tilde (1)), the lightest supersymmetric partners of the top quarks, in p (p) over bar collisions at a center-of-mass energy of 1.96 TeV, using data corresponding to an integrated luminosity of 7.3 fb(-1) collected with the D0 experiment at the Fermilab Tevatron Collider. Each scalar top quark is assumed to decay into a b quark, a charged lepton, and a scalar neutrino ((nu) over bar). We investigate final states arising from (t) over tilde (1)(t) over tilde (1) -> b (b) over bar mu tau(nu nu) over tilde and (t) over tilde (1)(t) over tilde (1) -> b (b) over bar tau tau(nu nu) over tilde. With no significant excess of events observed above the background expected from the standard model, we set exclusion limits on this production process in the (m((t) over tilde1), m((nu) over tilde)) plane.

  • 464.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Randall-Sundrum Gravitons in the Dielectron and Diphoton Final States with 5.4 fb-1 of Data from $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 104, p. 241802-Article in journal (Refereed)
  • 465.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Resonant Pair Production to Neutral Long-Lived Particles Decaying to $b\bar{b}$ in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 103, p. 071801-Article in journal (Refereed)
    Abstract [en]

     

     

     

  • 466.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Resonant WW and WZ Production in p(p)over-bar Collisions at root s=1.96 TeV2011In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 107, p. 011801-Article in journal (Refereed)
    Abstract [en]

    We search for resonant WW or WZ production by using up to 5: 4 fb(-1) of integrated luminosity collected by the D0 experiment in run II of the Fermilab Tevatron Collider. The data are consistent with the standard model background expectation, and we set limits on a resonance mass by using the sequential standard model W' boson and the Randall-Sundrum model graviton G as benchmarks. We exclude a sequential standard model W' boson in the mass range 180-690 GeV and a Randall-Sundrum graviton in the range 300-754 GeV at 95% C. L.

  • 467.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Scalar Bottom Quarks and Third-Generation Leptoquarks in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV2010In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 693, no 2, p. 95-101Article in journal (Refereed)
    Abstract [en]

    We report the results of a search for pair production of scalar bottom quarks () and scalar third-generation leptoquarks (LQ3) in 5.2 fb−1 of collisions at the D0 experiment of the Fermilab Tevatron Collider. Scalar bottom quarks are assumed to decay to a neutralino () and a b quark, and we set 95% C.L. lower limits on their production in the (, ) mass plane such as for and for . The leptoquarks are assumed to decay to a tau neutrino and a b quark, and we set a 95% C.L. lower limit of 247 GeV on the mass of a charge-1/3 third-generation scalar leptoquark.

  • 468.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Single Vectorlike Quarks in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV2011In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 106, no 8, p. 081801-Article in journal (Refereed)
    Abstract [en]

    We present a search for hypothetical vectorlike quarks in pp̅ collisions at √s=1.96  TeV. The data were collected by the D0 detector at the Fermilab Tevatron Collider and correspond to an integrated luminosity of 5.4  fb-1. We select events with a final state composed of a W or Z boson and a jet consistent with a heavy object decay. We observe no significant excess in comparison to the background prediction and set limits on production cross sections for vectorlike quarks decaying to W+jet and Z+jet. These are the most stringent limits to date for electroweak single vectorlike quark production at hadron colliders.

  • 469.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Squark Production in Events with Jets, Hadronically Decaying Tau Leptons and Missing Transverse Energy at $\sqrt{s}=1.96$ TeV2009In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 680, p. 24-33Article in journal (Refereed)
  • 470.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for the Associated Production of a b Quark and a Neutral Supersymmetric Higgs Boson which Decays into Tau Pairs2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 104, no 15, p. 151801-Article in journal (Refereed)
  • 471.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for the Rare Decay $B_s^0\to\mu^+\mu^-$2010In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 693, no 5, p. 539-544Article in journal (Refereed)
    Abstract [en]

    We present the results of a search for the flavor changing neutral current decay using 6.1 fb−1 of collisions at collected by the D0 experiment at the Fermilab Tevatron Collider. The observed number of candidates is consistent with background expectations. The resulting upper limit on the branching fraction is at the 95% C.L. This limit is a factor of 2.4 better than that of the previous D0 analysis and the best limit to date.

  • 472.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for the Standard Model Higgs Boson in the H -> WW -> lvq '(q)over-bar Decay Channel2011In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 106, no 17, p. 171802-Article in journal (Refereed)
    Abstract [en]

    We present a search for the standard model Higgs boson (H) in p (p) over bar collisions at root s = 1.96 TeV in events containing a charged lepton (l), missing transverse energy, and at least two jets, using 5.4 fb(-1) of integrated luminosity recorded with the D0 detector at the Fermilab Tevatron Collider. This analysis is sensitive primarily to Higgs bosons produced through the fusion of two gluons or two electroweak bosons, with subsequent decay H -> WW -> lvq'(q) over bar, where l is an electron or muon. The search is also sensitive to contributions from other production channels, such as WH -> lvb (b) over bar. In the absence of a signal, we set limits at the 95% C.L. on the cross section for H production sigma(p (p) over bar -> H + X) in these final states. For a mass of M(H) = 160 GeV, the limit is a factor of 3.9 larger than the cross section in the standard model and consistent with an a priori expected sensitivity of 5.0.

  • 473.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for the Standard Model Higgs Boson in the $ZH\to \nu\bar{\nu}b\bar{b}$ Channel in 5.2 fb$^{-1}$ of $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 104, p. 071801-Article in journal (Refereed)
    Abstract [en]

    A search is performed for the standard model Higgs boson in 5.2  fb-1 of pp̅        collisions at √s=1.96  TeV, collected with the D0 detector at the Fermilab Tevatron Collider. The final state considered is a pair of b jets and large missing transverse energy, as expected from pp̅        →ZH→νν̅        bb̅        production. The search is also sensitive to the WH→ℓνbb̅        channel when the charged lepton is not identified. For a Higgs boson mass of 115 GeV, a limit is set at the 95% C.L. on the cross section multiplied by branching fraction for [pp̅        →(Z/W)H](H→bb̅        ) that is a factor of 3.7 larger than the standard model value, consistent with the factor of 4.6 expected.

  • 474.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for Universal Extra Dimensions in p(p)over-bar Collisions2012In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 108, no 13, p. 131802-Article in journal (Refereed)
    Abstract [en]

    We present a search for Kaluza-Klein (KK) particles predicted by models with universal extra dimensions (UED) using a data set corresponding to an integrated luminosity of 7.3 fb(-1), collected by the D0 detector at a p (p) over bar center-of-mass energy of 1.96 TeV. The decay chain of KK particles can lead to a final state with two muons of the same charge. This signature is used to set a lower limit on the compactification scale of R-1 > 260 GeV in a minimal UED model.

  • 475.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for $WH$ Associated Production in 5.3 fb$^{-1}$ of $p\bar{p}$ Collisions at the Fermilab Tevatron2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 698, no 1, p. 6-13Article in journal (Refereed)
    Abstract [en]

    We present a search for associated production of Higgs and W bosons in collisions at a center of mass energy of in 5.3 fb−1 of integrated luminosity recorded by the D0 experiment. Multivariate analysis techniques are applied to events containing one lepton, an imbalance in transverse energy, and one or two b-tagged jets to discriminate a potential WH signal from Standard Model backgrounds. We observe good agreement between data and expected backgrounds, and set an upper limit of 4.5 (at 95% confidence level and for mH=115 GeV) on the ratio of the WH cross section multiplied by the branching fraction of to its Standard Model prediction, which is consistent with an expected limit of 4.8.

  • 476.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for WH associated production in p(p)over-bar collisions at root s=1.96 TeV2012In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 86, no 3, p. 032005-Article in journal (Refereed)
    Abstract [en]

    This report describes a search for associated production of W and Higgs bosons based on data corresponding to an integrated luminosity of L approximate to 5.3 fb(-1) collected with the D0 detector at the Fermilab Tevatron p (p) over bar Collider. Events containing a W -> l nu candidate (with l corresponding to e or mu) are selected in association with two or three reconstructed jets. One or two of the jets are required to be consistent with having evolved from a b quark. A multivariate discriminant technique is used to improve the separation of signal and backgrounds. Expected and observed upper limits are obtained for the product of the WH production cross section and branching ratios and reported in terms of ratios relative to the prediction of the standard model as a function of the mass of the Higgs boson (M-H). The observed and expected 95% C. L. upper limits obtained for an assumed M-H = 115 GeV are, respectively, factors of 4.5 and 4.8 larger than the value predicted by the standard model.

  • 477.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Search for $W^\prime\to tb$ Resonances with Left- and Right-Handed Couplings to Fermions2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 699, no 3, p. 145-150Article in journal (Refereed)
    Abstract [en]

    We present a search for the production of a heavy gauge boson, W, that decays to third-generation quarks, by D0 Collaboration in collisions at . We set 95% confidence level upper limits on the production cross section times branching fraction. For the first time, we set limits for arbitrary combinations of left- and right-handed couplings of the W boson to fermions. For couplings with the same strength as for the standard model W boson, we set the following limits, assuming that there are right-handed neutrinos νR for all three generations with M(W)>m(νR): M(W)>863 GeV for purely left-handed couplings, M(W)>885 GeV for purely right-handed couplings, and M(W)>916 GeV if both left- and right-handed couplings are present. The limit for right-handed couplings improves for M(W)<m(νR) to M(W)>890 GeV.

  • 478.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    The DØ Silicon Microstrip Tracker2011In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 634, no 1, p. 8-46Article in journal (Refereed)
    Abstract [en]

    This paper describes the mechanical design, the readout chain, the production, testing and the installation of the Silicon Microstrip Tracker of the D0 experiment at the Fermilab Tevatron collider. In addition, we describe the performance and operational experience of the detector during the experiment data collection between 2001 and 2010.

  • 479.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Wγ Production and Limits on Anomalous WWγ Couplings in pp̅ Collisions at √s=1.96  TeV2011In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 107, p. 241803-Article in journal (Refereed)
    Abstract [en]

    We measure the cross section and the difference in rapidities between photons and charged leptons for inclusive W(→lν)+γ production in eγ and μγ 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 →Wγ+X→lνγ+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 WWγ couplings for data from hadron colliders: -0.4<Δκγ<0.4 and -0.08<λγ<0.07 at the 95% C.L.

  • 480.
    Åsman, Barbro
    Stockholm University, Faculty of Science, Department of Physics.
    Z(gamma) production and limits on anomalous ZZ(gamma) and Z(gamma gamma) couplings in p(p)over-bar collisions at root s 1.96 TeV2012In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 85, no 5, p. 052001-Article in journal (Refereed)
    Abstract [en]

    We present a measurement of p (p) over bar -> Z gamma -> l(+)l(-)gamma (l = e, mu) production with a data sample corresponding to an integrated luminosity of 6.2 fb(-1) collected by the D0 detector at the Fermilab Tevatron p (p) over bar Collider. The results of the electron and muon channels are combined, and we measure the total production cross section and the differential cross section d(sigma)/dp(T)(gamma), where p(T)(gamma) is the momentum of the photon in the plane transverse to the beam line. The results obtained are consistent with the standard model predictions from next-to-leading order calculations. We use the transverse momentum spectrum of the photon to place limits on anomalous ZZ gamma and Z gamma gamma couplings.

  • 481.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Achenbach, R.
    Allbrooke, B. M. M.
    Anders, G.
    Andrei, V.
    Büscher, V.
    Bansil, H. S.
    Barnett, B. M.
    Bauss, B.
    Bendtz, Katarina
    Stockholm University, Faculty of Science, Department of Physics.
    Bohm, Christian
    Stockholm University, Faculty of Science, Department of Physics.
    Bracinik, J.
    Brawn, I. P.
    Brock, R.
    Buttinger, W.
    Caputo, R.
    Caughron, S.
    Cerrito, L.
    Charlton, D. G.
    Childers, J. T.
    Curtis, C. J.
    Daniells, A. C.
    Davis, A. O.
    Davygora, Y.
    Dorn, M.
    Eckweiler, S.
    Edmunds, D.
    Edwards, J. P.
    Eisenhandler, E.
    Ellis, K.
    Ermoline, Y.
    Föhlisch, F.
    Faulkner, P. J. W.
    Fedorko, W.
    Fleckner, J.
    French, S. T.
    Gee, C. N. P.
    Gillman, A. R.
    Goeringer, C.
    Hülsing, T.
    Hadley, D. R.
    Hanke, P.
    Hauser, R.
    Heim, S.
    Hellman, Sten
    Stockholm University, Faculty of Science, Department of Physics.
    Hickling, R. S.
    Hidvégi, A.
    Hillier, S. J.
    Hofmann, J. I.
    Hristova, I.
    Ji, W.
    Johansen, Marianne
    Stockholm University, Faculty of Science, Department of Physics.
    Keller, M.
    Khomich, A.
    Kluge, E. -E
    Koll, J.
    Laier, H.
    Landon, M. P. J.
    Lang, V. S.
    Laurens, P.
    Lepold, F.
    Lilley, J. N.
    Linnemann, J. T.
    Müller, F.
    Müller, T.
    Mahboubi, K.
    Martin, T. A.
    Mass, A.
    Meier, K.
    Meyer, C.
    Middleton, R. P.
    Moa, Torbjörn
    Stockholm University, Faculty of Science, Department of Physics.
    Moritz, S.
    Morris, J. D.
    Mudd, R. D.
    Narayan, R.
    Nedden, M. Zur
    Neusiedl, A.
    Newman, P. R.
    Nikiforov, A.
    Ohm, Christian C.
    CERN.
    Perera, V. J. O.
    Pfeiffer, U.
    Plucinski, Pawel
    Stockholm University, Faculty of Science, Department of Physics.
    Poddar, S.
    Prieur, D. P. F.
    Qian, W.
    Rieck, P.
    Rizvi, E.
    Sankey, D. P. C.
    Schäfer, U.
    Scharf, V.
    Schmitt, K.
    Schröder, C.
    Schultz-Coulon, H. -C
    Schumacher, C.
    Schwienhorst, R.
    Silverstein, Samuel B.
    Stockholm University, Faculty of Science, Department of Physics.
    Simioni, E.
    Snidero, G.
    Staley, R. J.
    Stamen, R.
    Stock, P.
    Stockton, M. C.
    Tan, C. L. A.
    Tapprogge, S.
    Thomas, J. P.
    Thompson, P. D.
    Thomson, M.
    True, P.
    Watkins, P. M.
    Watson, A. T.
    Watson, M. F.
    Wessels, M.
    Weber, P.
    Wiglesworthi, C.
    Williams, S. L.
    The ATLAS Level-1 Calorimeter Trigger: PreProcessor implementation and performance2012In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 7, article id P12008Article in journal (Refereed)
    Abstract [en]

    The PreProcessor system of the ATLAS Level-1 Calorimeter Trigger (L1Calo) receives about 7200 analogue signals from the electromagnetic and hadronic components of the calorimetric detector system. Lateral division results in cells which are pre-summed to so-called Trigger Towers of size 0.1 x 0.1 along azimuth (phi) and pseudorapidity (eta). The received calorimeter signals represent deposits of transverse energy. The system consists of 124 individual PreProcessor modules that digitise the input signals for each LHC collision, and provide energy and timing information to the digital processors of the L1Calo system, which identify physics objects forming much of the basis for the full ATLAS first level trigger decision. This paper describes the architecture of the PreProcessor, its hardware realisation, functionality, and performance.

  • 482.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Belanger-Champagne, C.
    Stockholm University, Faculty of Science, Department of Physics.
    b-Jet Identification in the D0 Experiment2010In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 620, p. 490-517Article in journal (Refereed)
    Abstract [en]

    Algorithms distinguishing jets originating from b quarks from other jet flavors are important tools in the physics program of the D0 experiment at the Fermilab Tevatron collider. This article describes the methods that have been used to identify b-quark jets, exploiting in particular the long lifetimes of b-flavored hadrons, and the calibration of the performance of these algorithms based on collider data.

  • 483.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Belanger-Champagne, C
    Stockholm University, Faculty of Science, Department of Physics.
    Combined Tevatron Upper Limit on $gg\to H\to W^+W^-$ and Constraints on the Higgs Boson Mass in Fourth-Generation Fermion Models2010In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 82, p. 011102-Article in journal (Refereed)
    Abstract [en]

    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

  • 484.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Belanger-Champagne, C.
    Stockholm University, Faculty of Science, Department of Physics.
    Measurement of the $t\bar{t}$ Cross Section Using High-Multiplicity Jet Events2010In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 82, p. 032002-Article in journal (Refereed)
    Abstract [en]

    We present a measurement of the tt̅ cross section using high-multiplicity jet events produced in pp̅ collisions at √s=1.96  TeV. These data were recorded at the Fermilab Tevatron Collider with the D0 detector. Events with at least six jets, two of them identified as b jets, were selected from a 1  fb-1 data set. The measured cross section, assuming a top quark mass of 175  GeV/c2, is 6.9±2.0  pb, in agreement with theoretical expectations.

  • 485.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Belanger-Champagne, C.
    Stockholm University, Faculty of Science, Department of Physics.
    Search for pair production of the scalar top quark in the electron plus muon final state2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 696, no 4, p. 321-327Article in journal (Refereed)
    Abstract [en]

    We report the result of a search for the pair production of the lightest supersymmetric partner of the top quark ((t) over tilde (1)) in p (p) over bar collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider corresponding to an integrated luminosity of 5.4 fb(-1). The scalar top quarks are assumed to decay into a b quark, a charged lepton, and a scalar neutrino ((nu) over bar). and the search is performed in the electron plus muon final state. No significant excess of events above the standard model prediction is detected, and substantially improved exclusion limits at the 95% C.L. are set in the the (M((t) over tilde1), M((nu) over tilde) mass plane.

  • 486.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Belanger-Champagne, C.
    Search for ZH -> l(+)l(-) b(b)over-bar Production in 4.2 fb(-1) of p(p)over-bar Collisions at root s=1.96 TeV2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 105, no 25, p. 251801-Article in journal (Refereed)
    Abstract [en]

    We present a search for the standard model Higgs boson produced in association with a Z boson in 4: 2 fb(-1) of p (p) over bar collisions, collected with the D0 detector at the Fermilab Tevatron at root 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 b-tagged jet. In the absence of an excess over the background expected from other standard model processes, limits on the ZH cross section multiplied by the branching ratios are set. The limit at M(H) = 115 GeV is a factor of 5.9 larger than the standard model prediction.

  • 487.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Uppsala University, Sweden.
    Belanger-Champagne, C.
    Stockholm University, Faculty of Science, Department of Physics. Uppsala University, Sweden.
    Buszello, C. P.
    Stockholm University, Faculty of Science, Department of Physics. Uppsala University, Sweden.
    Search for Doubly Charged Higgs Boson Pair Production in $p\bar{p}$ Collisions at √s=1.96 TeV2012In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 108, article id 021801Article in journal (Refereed)
    Abstract [en]

    We present a search for pair production of doubly charged Higgs bosons in the processes q (q) over bar -> H++H-- decaying through H-+/-+/- ->tau(+/-)tau(+/-), mu(+/-)tau(+/-), mu(+/-)mu(+/-). The search is performed in p (p) over bar collisions at a center-of-mass energy of root s = 1:96 TeV using an integrated luminosity of up to 7:0 fb(-1) collected by the D0 experiment at the Fermilab Tevatron Collider. The results are used to set 95% C. L. limits on the pair production cross section of doubly charged Higgs bosons and on their mass for different H-+/-+/- branching fractions. Models predicting different H-+/-+/- decays are investigated. Assuming B(H-+/-+/- -> tau(+/-)tau(+/-)) = 1 yields an observed (expected) lower limit on the mass of a left- handed H-L(+/-+/-) boson of 128 (116) GeV and assuming B(H-+/-+/- -> mu(+/-)tau(+/-)) = 1 the corresponding limits are 144 (149) GeV. In a model with B(H-+/-+/- -> tau +/-tau(+/-) B(H-+/-+/- -> mu(+/-)tau(+/-)) = B(H-+/-+/- -> mu(+/-)mu(+/-) ) 1/3, we obtain M(H-L(+/-+/-)) > 130 (138) GeV.

  • 488.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Uppsala University, Sweden.
    Belanger-Champagne, C.
    Uppsala University, Sweden.
    Buszello, C. P.
    Uppsala University, Sweden.
    Search for Higgs bosons decaying toτ+τ−pairs inp ̄pcollisions at√s=1.96 TeV2012In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 707, no 3-4, p. 323-329Article in journal (Refereed)
    Abstract [en]

    We present a search for the production of neutral Higgs bosons decaying into τ+τ pairs in collisions at a center-of-mass energy of 1.96 TeV. The data, corresponding to an integrated luminosity of 5.4 fb−1, were collected by the D0 experiment at the Fermilab Tevatron Collider. We set upper limits at the 95% C.L. on the product of production cross section and branching ratio for a scalar resonance decaying into τ+τ pairs, and we interpret these limits as limits on the production of Higgs bosons in the minimal supersymmetric standard model (MSSM) and as constraints in the MSSM parameter space.

  • 489.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Belanger-Champagne, C.
    Stockholm University.
    Clement, C.
    Stockholm University.
    Gollub, N.
    Stockholm University.
    Hansson, P.
    Stockholm University.
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Study of the decay B-s(0)->(DsDs(*))-D-(*)2007In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 99, no 24, p. 241801-Article in journal (Refereed)
    Abstract [en]

    We report a study of the decay B-s(0)->(DsDs(*))-D-(*) using a data sample corresponding to 1.3 fb(-1) of integrated luminosity collected by the D0 experiment in 2002-2006 during run II of the Fermilab Tevatron collider. One D-s((*)) meson was partially reconstructed in the decay D-s ->phi mu nu, and the other D-s((*)) meson was identified using the decay D-s ->phi pi where no attempt was made to distinguish D-s and D-s(*) states. For the branching fraction Br(B-s(0)->(DsDs(*))-D-(*)) we obtain a 90% C.L. range [0.002,0.080] and central value 0.039(-0.017)(+0.019)(stat)(-0.015)(+0.016)(syst). This was subsequently used to make the most precise estimate of the width difference Delta Gamma(CP)(s) in the B-s(0)-(B)over bar(s)(0) system: Delta Gamma(CP)(s)/Gamma(s)=0.079(-0.035)(+0.038)(stat)(-0.030)(+0.031)(syst).

  • 490.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Belanger-Champagne, C.
    Gollub, N.
    Hansson, P.
    Lehner, F.
    Strandberg, S.
    Measurement of the p(p)over-bar -> WZ+X cross section at root s=1.96 TeV and limits on WWZ trilinear gauge couplings2007In: Physical Review D, ISSN 1550-7998, Vol. 76, no 11, p. 111104-Article in journal (Refereed)
    Abstract [en]

    We present measurements of the process p (P) over bar -> WZ + X -> l 'nu(l ')l (l) over bar at root s = 1:96 TeV,where l and l ' are electrons or muons. Using 1 fb(-1) of data from the D0 experiment, we observe 13 candidates with an expected background of 4.5 +/- 0.6 events and measure a cross section sigma(WZ) = 2.7(-1.3)(+1.7) pb. From the number of observed events and the Z boson transverse momentum distribution, we limit the trilinear WWZ gauge couplings to -0: 17 <= lambda(Z) <= 0.21 (Delta k(Z) <= 0.29(lambda(Z) = 0) at the 95% C.L. for a form factor scale Lambda = 2 TeV. Further, assuming that Delta g(1)(Z) = Delta k(Z), we find -0.12 <= Delta k(Z) <= 0.29(lambda(Z) = 0) at the 95% C. L. These are the most restrictive limits on the WWZ couplings available to date.

  • 491.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Belanger-Champagne, C.
    Stockholm University.
    Gollub, N.
    Stockholm University.
    Hansson, P.
    Stockholm University.
    Strandberg, J.
    Stockholm University.
    Search for W ' bosons decaying to an electron and a neutrino with the D0 detector2008In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 100, no 3, p. 31804-Article in journal (Refereed)
    Abstract [en]

    This Letter describes the search for a new heavy charged gauge boson W-' decaying into an electron and a neutrino. The data were collected with the D0 detector at the Fermilab Tevatron p (p) over bar Collider at root s=1.96 TeV, and correspond to an integrated luminosity of about 1 fb(-1). Lacking any significant excess in the data in comparison with known processes, an upper limit is set on sigma(')(W)xB(W-'-> e nu), and a W-' boson with mass below 1.00 TeV can be excluded at the 95% C.L., assuming standard-model-like couplings to fermions. This result significantly improves upon previous limits and is the most stringent to date.

  • 492.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Belanger-Champagne, C.
    Stockholm University.
    Gollub, N.
    Stockholm University.
    Hansson, P.
    Stockholm University.
    Strandberg, S.
    Stockholm University.
    Search for ZZ and z gamma* production in p(p)over-bar collisions at root s=1.96 TeV and limits on anomalous ZZZ and ZZ gamma* couplings2008In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 100, no 13, p. 131801-Article in journal (Refereed)
    Abstract [en]

    We present a study of mu mu mu mu, eeee, and mu mu ee events using 1 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron p (p) over bar Collider at root s = 1.96 TeV. Requiring the lepton pair masses to be greater than 30 GeV, we observe one event, consistent with the expected background of 0.13 +/- 0.03 events and with the predicted standard model ZZ and Z gamma(*) production of 1.71 +/- 0.15 events. We set an upper limit on the ZZ and Z gamma(*) cross section of 4.4 pb at the 95% C.L. We also derive limits on anomalous neutral trilinear ZZZ and ZZ gamma(*) gauge couplings. The one-parameter 95% C.L. coupling limits with a form-factor scale Lambda = 1.2 TeV are -0.28 < f(40)(Z)< 0.28, -0.31 < f(50)(Z)< 0.29, -0.26 < f(40)(gamma)< 0.26, and -0.30 < f(50)(gamma)< 0.28.

  • 493.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Belanger-Champagne, C.
    Stockholm University, Faculty of Science, Department of Physics.
    Gollub, N.
    Stockholm University, Faculty of Science, Department of Physics.
    Strandberg, J.
    Stockholm University.
    Search for Anomalous Wtb Couplings in Single Top Quark Production2008In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 101, no 22, p. 221801-Article in journal (Refereed)
    Abstract [en]

    In 0.9 fb(-1) of pp collisions, the D0 Collaboration presented evidence for single top quark production in events with an isolated lepton, missing transverse momentum, and two to four jets. We examine these data to study the Lorentz structure of the Wtb coupling. The standard model predicts a left-handed vector coupling at the Wtb vertex. The most general lowest dimension, CP-conserving Lagrangian admits right-handed vector and left- or right-handed tensor couplings as well. We find that the data prefer the left-handed vector coupling and set upper limits on the anomalous couplings. These are the first direct constraints on a general Wtb interaction and the first direct limits on left- and right-handed tensor couplings.

  • 494.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Belanger-Champagne, C.
    Stockholm University.
    Gollub, N.
    Stockholm University.
    Strandberg, S.
    Stockholm University.
    Measurement of the t(t)over-bar production cross section in p(p)over-bar collisions at root s=1.96 TeV2008In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 100, no 19, p. 192004-Article in journal (Refereed)
    Abstract [en]

    We measure the t (t) over bar production cross section in p (p) over bar collisions at root s = 1.96 TeV in the lepton + jets channel. Two complementary methods discriminate between signal and background: b tagging and a kinematic likelihood discriminant. Based on 0.9 fb(-1) of data collected by the D0 detector at the Fermilab Tevatron Collider, we measure sigma(t (t) over bar) = 7.62 +/- 0.85 pb, assuming the current world average m(t) = 172.6 GeV. We compare our cross section measurement with theory predictions to determine a value for the top-quark mass of 170 +/- 7 GeV.

  • 495.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Belanger-Champagne, C.
    Stockholm University.
    Gollub, N.
    Stockholm University.
    Strandberg, S.
    Stockholm University.
    Observation of the B-c meson in the exclusive decay B-c -> J/psi pi2008In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 101, no 1, p. 12001-Article in journal (Refereed)
    Abstract [en]

    A fully reconstructed B-c -> J/psi pi signal is observed with the D0 detector at the Fermilab Tevatron p (p) over bar collider using 1.3 fb(-1) of integrated luminosity. The signal consists of 54 +/- 12 candidates with a significance that exceeds 5 standard deviations, and confirms earlier observations of this decay. The measured mass of the B-c meson is 6300 +/- 14(stat)+/- 5(syst) MeV/c(2).

  • 496.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Belanger-Champagne, C.
    Stockholm University.
    Gollub, N.
    Stockholm University.
    Strandberg, S.
    Search for W ' boson resonances decaying to a top quark and a bottom quark2008In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 100, no 21, p. 211803-Article in journal (Refereed)
    Abstract [en]

    We search for the production of a heavy W ' gauge boson that decays to third generation quarks in 0: 9 fb(-1) of p (p) over bar collisions at root s = 1: 96 TeV, collected with the D0 detector at the Fermilab Tevatron collider. We find no significant excess in the final-state invariant mass distribution and set upper limits on the production cross section times branching fraction. For a left-handed W ' boson with SM couplings, we set a lower mass limit of 731 GeV. For right-handed W ' bosons, we set lower mass limits of 739 GeV if the W ' boson decays to both leptons and quarks and 768 GeV if the W ' boson decays only to quarks. We also set limits on the coupling of the W ' boson to fermions as a function of its mass.

  • 497.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Belanger-Champagne, C.
    Gollub, N.
    Stockholm University.
    Strandberg, S.
    ZZ -> l(+)l(-)nu(nu)overbar production in p(p)overbar collisions at root s=1.96 TeV2008In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 78, no 7, p. 72002-Article in journal (Refereed)
    Abstract [en]

    We describe a search for Z boson pair production in p(p)overbar collisions at root s=1.96 TeV with the D0 detector at the Fermilab Tevatron Collider using a data sample corresponding to an integrated luminosity of 2.7 fb(-1). Using the final state decay ZZ ->center dot(+)center dot(-)nu(nu)overbar (where center dot=e or mu) we find a signal with a 2.6 standard deviations significance (2.0 expected) corresponding to a cross section of sigma(p(p)overbar -> ZZ+X)=2.01 +/- 0.93(stat)+/- 0.29(sys) pb.

  • 498.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bendtz, Katarina
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bohm, Christian
    Stockholm University, Faculty of Science, Department of Physics.
    Clément, Christophe
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Eriksson, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Gellerstedt, Karl
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hellman, Sten
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Holmgren, Sven-Olof
    Stockholm University, Faculty of Science, Department of Physics.
    Johansen, M.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Johansson, K. E.
    Stockholm University, Faculty of Science, Department of Physics.
    Jon-And, Kerstin
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Khandanyan, Hovhannes
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kim, Hyeon Jin
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Klimek, Pawel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Lundberg, Johan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Lundberg, Olle
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Milstead, David
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Mjörnmark, J. U.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Moa, Torbjörn
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ohm, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). CERN, Geneva, Switzerland.
    Papadelis, Aras
    Stockholm University, Faculty of Science, Department of Physics.
    Sellden, Björn
    Stockholm University, Faculty of Science, Department of Physics.
    Silverstein, Samuel
    Stockholm University, Faculty of Science, Department of Physics.
    Sjölin, Jörgen
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Tylmad, Maja
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Yang, Zhaoyu
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Measurement of the flavour composition of dijet events in pp collisions at root s=7 TeV with the ATLAS detector2013In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 73, no 2, p. 2301-Article in journal (Refereed)
    Abstract [en]

    This paper describes a measurement of the flavour composition of dijet events produced in pp collisions at root s = 7 TeV using the ATLAS detector. The measurement uses the full 2010 data sample, corresponding to an integrated luminosity of 39 pb(-1). Six possible combinations of light, charm and bottom jets are identified in the dijet events, where the jet flavour is defined by the presence of bottom, charm or solely light flavour hadrons in the jet. Kinematic variables, based on the properties of displaced decay vertices and optimised for jet flavour identification, are used in a multidimensional template fit to measure the fractions of these dijet flavour states as functions of the leading jet transverse momentum in the range 40 GeV to 500 GeV and jet rapidity vertical bar y vertical bar < 2.1. The fit results agree with the predictions of leading-and next-to-leading-order calculations, with the exception of the dijet fraction composed of bottom and light flavour jets, which is underestimated by all models at large transverse jet momenta. The ability to identify jets containing two b-hadrons, originating from e. g. gluon splitting, is demonstrated. The difference between bottom jet production rates in leading and subleading jets is consistent with the next-to-leading-order predictions.

  • 499.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bendtz, Katarina
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bohm, Christian
    Stockholm University, Faculty of Science, Department of Physics.
    Clément, Christophe
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Eriksson, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Gellerstedt, Karl
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hellman, Sten
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Holmgren, Sven-Olof
    Stockholm University, Faculty of Science, Department of Physics.
    Johansen, M.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Johansson, K. E.
    Stockholm University, Faculty of Science, Department of Physics.
    Jon-And, Kerstin
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Khandanyan, Hovhannes
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kim, Hyeon Jin
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Klimek, Pawel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Lundberg, Johan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Lundberg, Olle
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Milstead, David
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Moa, Torbjörn
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ohm, C. C.
    CERN, Geneva, Switzerland.
    Papadelis, Aras
    Stockholm University, Faculty of Science, Department of Physics.
    Sellden, Björn
    Stockholm University, Faculty of Science, Department of Physics.
    Silverstein, Samuel
    Stockholm University, Faculty of Science, Department of Physics.
    Sjölin, Jörgen
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Tylmad, Maja
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Yang, Zhaoyu
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Measurement of charged-particle event shape variables in inclusive root(s)=7 TeV proton-proton interactions with the ATLAS detector2013In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 88, no 3, p. UNSP 032004-Article in journal (Refereed)
    Abstract [en]

    The measurement of charged-particle event shape variables is presented in inclusive inelastic pp collisions at a center-of-mass energy of 7 TeV using the ATLAS detector at the LHC. The observables studied are the transverse thrust, thrust minor, and transverse sphericity, each defined using the final-state charged particles' momentum components perpendicular to the beam direction. Events with at least six charged particles are selected by a minimum-bias trigger. In addition to the differential distributions, the evolution of each event shape variable as a function of the leading charged-particle transverse momentum, charged-particle multiplicity, and summed transverse momentum is presented. Predictions from several Monte Carlo models show significant deviations from data.

  • 500.
    Åsman, Barbro
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bendtz, Katarina
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bohm, Christian
    Stockholm University, Faculty of Science, Department of Physics.
    Clément, Christophe
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Eriksson, Daniel
    Stockholm University, Faculty of Science, Department of Physics.
    Gellerstedt, Karl
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hellman, Sten
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Holmgren, Sven-Olof
    Stockholm University, Faculty of Science, Department of Physics.
    Johansen, M.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Johansson, K. E.
    Stockholm University, Faculty of Science, Department of Physics.
    Jon-And, Kerstin
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Khandanyan, Hovhannes
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kim, Hyeon Jin
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Klimek, Pawel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Lundberg, Johan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Lundberg, Olle
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Milstead, David
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Moa, Torbjörn
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ohm, C. C.
    CERN, Geneva, Switzerland.
    Papadelis, Aras
    Stockholm University, Faculty of Science, Department of Physics.
    Silverstein, Samuel
    Stockholm University, Faculty of Science, Department of Physics.
    Sjölin, Jörgen
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Strandberg, Sara
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Tylmad, Maja
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Yang, Zhaoyu
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Search for resonant diboson production in the WW/WZ -> lvjj decay channels with the ATLAS detector at root s=7 TeV2013In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 87, no 11, p. 112006-Article in journal (Refereed)
    Abstract [en]

    A search for resonant diboson production using a data sample corresponding to 4.7 fb(-1) of integrated luminosity collected by the ATLAS experiment at the Large Hadron Collider in pp collisions at root s = 7 TeV is presented. The search for a narrow resonance in the WW or WZ mass distribution is conducted in a final state with an electron or a muon, missing transverse momentum, and at least two jets. No significant excess is observed and limits are set using three benchmark models: WW resonance masses below 940 and 710 GeV are excluded at 95% confidence level for spin-2 Randall-Sundrum and bulk Randall-Sundrum gravitons, respectively; WZ resonance masses below 950 GeV are excluded at 95% confidence level for a spin-1 extended gauge model W' boson.

78910111213 451 - 500 of 791
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