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  • 51. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    University of Chicago.
    Zychacek, V.
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    et, al
    The ATLAS Experiment at the CERN Large Hadron Collider2008Inngår i: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 3, s. S08003-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ATLAS detector as installed in its experimental cavern at point 1 at CERN is described in this paper. A brief overview of the expected performance of the detector when the Large Hadron Collider begins operation is also presented.

  • 52. Aad, G.
    et al.
    Lafaye, Remi
    Cern.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Measurement of the W(+/-)Z production cross section and limits on anomalous triple gauge couplings in proton-proton collisions at root s=7 TeV with the ATLAS detector2012Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 709, nr 4-5, s. 341-357Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This Letter presents a measurement of W(+/-)Z production in 1.02 fb(-1) of pp collision data at root s = 7 TeV collected by the ATLAS experiment in 2011. Doubly leptonic decay events are selected with electrons, muons and missing transverse momentum in the final state. In total 71 candidates are observed, with a background expectation of 12.1 +/- 1.4(stat.)(-2.0)(+4.1)(syst.) events. The total cross section for W(+/-)Z production for Z/gamma* masses within the range 66 GeV to 116 GeV is determined to be sigma(tot)(WZ) = 20.5(-2.8)(+3.1)(stat.)(-1.3)(+1.4)(syst)(-0.8)(+0.9)(lumi.) pb, which is consistent with the Standard Model expectation of 17.3(0.8)(+1.3) pb. Limits on anomalous triple gauge boson couplings are extracted.

  • 53. Aad, G.
    et al.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al
    Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at root s=7 TeV with the ATLAS detector2011Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 71, nr 12, s. 1846-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The inclusive and dijet production cross-sections have been measured for jets containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass energy of root s = 7 TeV, using the ATLAS detector at the LHC. The measurements use data corresponding to an integrated luminosity of 34 pb(-1). The b-jets are identified using either a lifetime-based method, where secondary decay vertices of b-hadrons in jets are reconstructed using information from the tracking detectors, or a muon-based method where the presence of a muon is used to identify semileptonic decays of b-hadrons inside jets. The inclusive b-jet cross-section is measured as a function of transverse momentum in the range 20 < p(T) < 400 GeV and rapidity in the range vertical bar y vertical bar < 2.1. The b<(b)over bar>-dijet cross-section is measured as a function of the dijet invariant mass in the range 110 < m(jj) < 760 GeV, the azimuthal angle difference between the two jets and the angular variable chi in two dijet mass regions. The results are compared with next-to-leading-order QCD predictions. Good agreement is observed between the measured cross-sections and the predictions obtained using POWHEG + Pythia. MC@NLO + Herwig shows good agreement with the measured b (b) over bar -dijet cross-section. However, it does not reproduce the measured inclusive cross-section well, particularly for central b-jets with large transverse momenta.

  • 54. Aad, G.
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    et, al.
    Expected Performance of the ATLAS Experiment: Detector, Trigger and Physics2009Manuskript (preprint) (Annet vitenskapelig)
  • 55. Aad, Georges
    et al.
    Grahn, Karl Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L
    et, al
    Measurement of the inclusive isolated prompt photon cross section in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector2011Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 83, nr 5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A measurement of the cross section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy root s = 7 TeV is presented. The measurement covers the pseudorapidity ranges vertical bar eta(gamma)vertical bar < 1: 37 and 1: 52 <= vertical bar eta(gamma)vertical bar < 1: 81 in the transverse energy range 15 <= E(T)(gamma) < 100 GeV. The results are based on an integrated luminosity of 880 nb(-1), collected with the ATLAS detector at the Large Hadron Collider. Photon candidates are identified by combining information from the calorimeters and from the inner tracker. Residual background in the selected sample is estimated from data based on the observed distribution of the transverse isolation energy in a narrow cone around the photon candidate. The results are compared to predictions from next-to-leading-order perturbative QCD calculations.

  • 56. Aad, Georges
    et al.
    Jovicevic, Jelena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    LAPP, CNRS/IN2P3 and Université de Savoie, Annecy-le-Vieux, France.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for heavy vector-like quarks coupling to light quarks in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector2012Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 712, nr 1-2, s. 22-39Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This letter presents a search for singly produced vector-like quarks, Q, coupling to light quarks, q. The search is sensitive to both charged current (CC) and neutral current (NC) processes, p p --> Q q --> W q q' and p p --> Q q --> Z q q' with a leptonic decay of the vector gauge boson. In 1.04/fb of data taken in 2011 by the ATLAS experiment at a center-of-mass energy sqrt(s) = 7 TeV, no evidence of such heavy vector-like quarks is observed above the expected Standard Model background. Limits on the heavy vector-like quark production cross section times branching ratio as a function of mass m_Q are obtained. For a coupling kappa_(qQ) = v/m_Q, where v is the Higgs vacuum expectation value, 95% C.L. lower limits on the mass of a vector-like quark are set at 900 GeV and 760 GeV from CC and NC processes, respectively.

  • 57. Aad, Georges
    et al.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for anomalous production of prompt like-sign muon pairs and constraints on physics beyond the standard model with the ATLAS detector2012Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 85, nr 3, s. 032004-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An inclusive search for anomalous production of two prompt, isolated muons with the same electric charge is presented. The search is performed in a data sample corresponding to 1.6 fb(-1) of integrated luminosity collected in 2011 at root s = 7 TeV with the ATLAS detector at the LHC. Muon pairs are selected by requiring two isolated muons of the same electric charge with p(T) > 20 GeV and vertical bar eta vertical bar < 2.5. Minimal requirements are placed on the rest of the event activity. The distribution of the invariant mass of the muon pair m(mu mu) is found to agree well with the background expectation. Upper limits on the cross section for anomalous production of two muons with the same electric charge are placed as a function of m(mu mu) within a fiducial region defined by the event selection. The fiducial cross-section limit constrains the like-sign top-quark pair-production cross section to be below 3.7 pb at 95% confidence level. The data are also analyzed to search for a narrow like-sign dimuon resonance as predicted for e. g. doubly charged Higgs bosons (H-+/-+/-). Assuming pair production of H-+/-+/- bosons and a branching ratio to muons of 100% (33%), this analysis excludes masses below 355 (244) GeV and 251 (209) GeV for H-+/-+/- bosons coupling to left-handed and right-handed fermions, respectively.

  • 58. Aad, Georges
    et al.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    LAPP, CNRS/IN2P3 and Université de Savoie, Annecy-le-Vieux, France.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for contact interactions in dilepton events from pp collisions at sqrt(s) = 7 TeV with the ATLAS detector2012Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 712, nr 1-2, s. 40-58Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This Letter presents a search for contact interactions in the dielectron and dimuon channels using data from proton-proton collisions produced by the LHC at sqrt(s) = 7 TeV and recorded by the ATLAS detector. The data sample, collected in 2011, corresponds to an integrated luminosity of 1.08 and 1.21 fb^-1 in the e+ e- and mu+ mu- channels, respectively. No significant deviations from the standard model are observed. Using a Bayesian approach with a prior flat in 1/Lambda^2, the following 95% CL lower limits are placed on the energy scale of llqq contact interactions: Lambda^- > 10.1 TeV (Lambda^+ > 9.4 TeV) in the electron channel and Lambda^- > 8.0 TeV (Lambda^+ > 7.0 TeV) in the muon channel for constructive (destructive) interference in the left-left isoscalar contact interaction model. Limits are also provided for a prior flat in 1/Lambda^4.

  • 59. Aad, Georges
    et al.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for first generation scalar leptoquarks in pp collisions at root s=7 TeV with the ATLAS detector2012Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 709, nr 3, s. 158-176Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report a search for first generation scalar leptoquarks using 1.03 fb(-1) of proton-proton collisions data produced by the Large Hadron Collider at root s = 7 TeV and recorded by the ATLAS experiment. Leptoquarks are sought via their decay into an electron or neutrino and a quark, producing events with two oppositely charged electrons and at least two jets, or events with an electron, missing transverse momentum and at least two jets. Control data samples are used to validate background predictions from Monte Carlo simulation. In the signal region, the observed event yields are consistent with the background expectations. We exclude at 95% confidence level the production of first generation scalar leptoquark with masses m(LQ) < 660 (607) GeV when assuming the branching fraction of a leptoquark to a charged lepton is equal to 1.0 (0.5).

  • 60. Aad, Georges
    et al.
    Kuwertz, Emma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    Cern.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for Scalar Bottom Quark Pair Production with the ATLAS Detector in pp Collisions at root s=7 TeV2012Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 108, nr 18, s. 181802-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The results of a search for pair production of the scalar partners of bottom quarks in 2: 05 fb(-1) of pp collisions at root s = 7 TeV using the ATLAS experiment are reported. Scalar bottom quarks are searched for in events with large missing transverse momentum and two jets in the final state, where both jets are identified as originating from a bottom quark. In an R-parity conserving minimal supersymmetric scenario, assuming that the scalar bottom quark decays exclusively into a bottom quark and a neutralino, 95% confidence-level upper limits are obtained in the (b) over tilde (1) - (chi) over tilde (0)(1) mass plane such that for neutralino masses below 60 GeV scalar bottom masses up to 390 GeV are excluded.

  • 61. Aad, Georges
    et al.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al.
    Measurement of the cross section for the production of a W boson in association with b-jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector2012Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 707, nr 5, s. 418-437Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A measurement is presented of the cross section for the production of a W boson with one or two jets, of which at least one must be a b-jet, in pp collisions at root s = 7 TeV. Production via top decay is not included in the signal definition. The measurement is based on 35 pb(-1) of data collected with the ATLAS detector at the LHC. The W + b-jet cross section is defined for jets reconstructed with the anti-k(t) clustering algorithm with transverse momentum above 25 GeV and rapidity within +/-2.1. The b-jets are identified by reconstructing secondary vertices. The fiducial cross section is measured both for the electron and muon decay channel of the W boson and is found to be 10.2 +/- 1.9(stat) +/- 2.6(syst) pb for one lepton flavour. The results are compared with next-to-leading order QCD calculations, which predict a cross section smaller than, though consistent with, the measured value.

  • 62. Aad, Georges
    et al.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    A measurement of the ratio of the W and Z cross sections with exactly one associated jet in pp collisions at root s=7 TeV with ATLAS2012Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 708, nr 3-5, s. 221-240Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ratio of production cross sections of the W and Z bosons with exactly one associated jet is presented as a function of jet transverse momentum threshold. The measurement has been designed to maximise cancellation of experimental and theoretical uncertainties, and is reported both within a particle-level kinematic range corresponding to the detector acceptance and as a total cross-section ratio. Results are obtained with the ATLAS detector at the LHC in pp collisions at a centre-of-mass energy of 7 TeV using an integrated luminosity of 33 pb(-1). The results are compared with perturbative leading-order, leading-log, and next-to-leading-order QCD predictions, and are found to agree within experimental and theoretical uncertainties. The ratio is measured for events with a single jet with p(T) > 30 GeV to be 8.73 +/- 0.30(stat) +/- 0.40(syst) in the electron channel, and 8.49 +/- 0.23(stat) +/- 0.33(syst) in the muon channel.

  • 63. Aad, Georges
    et al.
    Lafaye, Remi
    Cern.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    A study of the material in the ATLAS inner detector using secondary hadronic interactions2012Inngår i: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 7, s. P01013-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ATLAS inner detector is used to reconstruct secondary vertices due to hadronic interactions of primary collision products, so probing the location and amount of material in the inner region of ATLAS. Data collected in 7 TeV pp collisions at the LHC, with a minimum bias trigger, are used for comparisons with simulated events. The reconstructed secondary vertices have spatial resolutions ranging from similar to 200 mu m to 1 mm. The overall material description in the simulation is validated to within an experimental uncertainty of about 7%. This will lead to a better understanding of the reconstruction of various objects such as tracks, leptons, jets, and missing transverse momentum.

  • 64. Aad, Georges
    et al.
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Electron performance measurements with the ATLAS detector using the 2010 LHC proton-proton collision data2012Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 72, nr 3, s. 1909-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Detailed measurements of the electron performance of the ATLAS detector at the LHC are reported, using decays of the Z, W and J/psi particles. Data collected in 2010 at root s = 7 TeV are used, corresponding to an integrated luminosity of almost 40 pb(-1). The inter-alignment of the inner detector and the electromagnetic calorimeter, the determination of the electron energy scale and resolution, and the performance in terms of response uniformity and linearity are discussed. The electron identification, reconstruction and trigger efficiencies, as well as the charge misidentification probability, are also presented.

  • 65. Aad, Georges
    et al.
    Lafaye, Remi
    Cern.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Inclusive search for same-sign dilepton signatures in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector2011Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 10, s. 107-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An inclusive search is presented for new physics in events with two isolated leptons (electron or muon) having the same electric charge. The data are selected from events collected from pp collisions at sqrt(s) = 7 TeV by the ATLAS detector and correspond to an integrated luminosity of 34 inverse picobarns. The spectra in dilepton invariant mass, missing transverse momentum and jet multiplicity are presented and compared to Standard Model predictions. In this event sample, no evidence is found for contributions beyond those of the Standard Model. Limits are set on the cross-section in a fiducial region for new sources of same-sign high-mass dilepton events in the di-electron, di-muon and electron-muon channels. Four models predicting same-sign dilepton signals are constrained: two descriptions of Majorana neutrinos, a cascade topology similar to supersymmetry or universal extra dimensions, and fourth generation down-type quarks. Assuming a new physics scale of 1 TeV, Majorana neutrinos produced by an effective operator V with masses below 460 GeV are excluded at 95% confidence level. A lower limit of 290 GeV is set at 95% confidence level on the mass of fourth generation down type quarks.

  • 66. Aad, Georges
    et al.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et, al.
    Measurement of the isolated diphoton cross section in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector2012Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 85, nr 1, s. 012003-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ATLAS experiment has measured the production cross section of events with two isolated photons in the final state, in proton-proton collisions at root s = 7 TeV. The full data set acquired in 2010 is used, corresponding to an integrated luminosity of 37 pb(-1). The background, consisting of hadronic jets and isolated electrons, is estimated with fully data-driven techniques and subtracted. The differential cross sections, as functions of the di-photon mass (m(gamma gamma)), total transverse momentum (p(T),(gamma gamma)), and azimuthal separation (Delta phi(gamma gamma)), are presented and compared to the predictions of next-to-leading-order QCD.

  • 67. Aad, Georges
    et al.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Measurement of the pseudorapidity and transverse momentum dependence of the elliptic flow of charged particles in lead-lead collisions at root s(NN)=2.76 TeV with the ATLAS detector2012Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 707, nr 3-4, s. 330-348Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This Letter describes the measurement of elliptic flow of charged particles in lead-lead collisions at root s(NN) = 2.76 TeV using the ATLAS detector at the Large Hadron Collider (LHC). The results are based on an integrated luminosity of approximately 7 mu b(-1). Elliptic flow is measured over a wide region in pseudorapidity, vertical bar eta vertical bar < 2.5, and over a broad range in transverse momentum, 0.5 < p(T) < 20 GeV. The elliptic flow parameter nu(2) is obtained by correlating individual tracks with the event plane measured using energy deposited in the forward calorimeters. As a function of transverse momentum, nu(2)(p(T)) reaches a maximum at p(T) of about 3 GeV. then decreases and becomes weakly dependent on p(T) above 7-8 GeV. Over the measured pseudorapidity region, nu(2) is found to be only weakly dependent on eta, with less variation than observed at lower beam energies. The results are discussed in the context of previous measurements at lower collision energies, as well as recent results from the LHC.

  • 68. Aad, Georges
    et al.
    Lafaye, Remi
    Cern.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Measurement of the top quark pair production cross-section with ATLAS in the single lepton channel2012Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 711, nr 3-4, s. 244-263Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A measurement of the production cross-section for top quark pairs (t (t) over bar) in pp collisions at root s = 7 TeV is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in the single lepton topology by requiring an electron or muon, large missing transverse momentum and at least three jets. With a data sample of 35 pb(-1), two different multivariate methods, one of which uses b-quark jet identification while the other does not, use kinematic variables to obtain cross-section measurements of sigma(t (t) over bar) = 187 +/- 11(stat.)(-17)(+18)(syst.) +/- 6(lumi.) pb and sigma(t (t) over bar) = 173 +/- 17(stat.)(-16)(+18)(syst.) +/- 6(lumi.) pb respectively. The two measurements are in agreement with each other and with QCD calculations. The first measurement has a better a priori sensitivity and constitutes the main result of this Letter.

  • 69. Aad, Georges
    et al.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Performance of missing transverse momentum reconstruction in proton-proton collisions at root s=7 TeV with ATLAS2012Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 72, nr 1, s. 1844-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The measurement of missing transverse momentum in the ATLAS detector, described in this paper, makes use of the full event reconstruction and a calibration based on reconstructed physics objects. The performance of the missing transverse momentum reconstruction is evaluated using data collected in pp collisions at a centre-of-mass energy of 7 TeV in 2010. Minimum bias events and events with jets of hadrons are used from data samples corresponding to an integrated luminosity of about 0.3 nb(-1) and 600 nb(-1) respectively, together with events containing a Z boson decaying to two leptons (electrons or muons) or a W boson decaying to a lepton (electron or muon) and a neutrino, from a data sample corresponding to an integrated luminosity of about 36 pb(-1). An estimate of the systematic uncertainty on the missing transverse momentum scale is presented.

  • 70. Aad, Georges
    et al.
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Performance of the ATLAS Trigger System in 20102012Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 72, nr 1, s. 1849-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Proton-proton collisions at root s = 7 TeV and heavy ion collisions at root(NN)-N-s = 2.76 TeV were produced by the LHC and recorded using the ATLAS experiment's trigger system in 2010. The LHC is designed with a maximum bunch crossing rate of 40 MHz and the ATLAS trigger system is designed to record approximately 200 of these per second. The trigger system selects events by rapidly identifying signatures of muon, electron, photon, tau lepton, jet, and B meson candidates, as well as using global event signatures, such as missing transverse energy. An overview of the ATLAS trigger system, the evolution of the system during 2010 and the performance of the trigger system components and selections based on the 2010 collision data are shown. A brief outline of plans for the trigger system in 2011 is presented.

  • 71. Aad, Georges
    et al.
    Lafaye, Remi
    Cern.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for decays of stopped, long-lived particles from 7 TeV pp collisions with the ATLAS detector2012Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 72, nr 4, s. 1965-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    New metastable massive particles with electric and colour charge are features of many theories beyond the Standard Model. A search is performed for long-lived gluino-based R-hadrons with the ATLAS detector at the LHC using a data sample corresponding to an integrated luminosity of 31 pb(-1). We search for evidence of particles that have come to rest in the ATLAS detector and decay at some later time during the periods in the LHC bunch structure without proton-proton collisions. No significant deviations from the expected backgrounds are observed, and a cross-section limit is set. It can be interpreted as excluding gluino-based R-hadrons with masses less than 341 GeV at the 95 % C.L., for lifetimes from 10(-5) to 10(3) seconds and a neutralino mass of 100 GeV.

  • 72. Aad, Georges
    et al.
    Lafaye, Remi
    Cern.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for diphoton events with large missing transverse momentum in 1 fb(-1) of 7 TeV proton-proton collision data with the ATLAS detector ATLAS Collaboration2012Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 710, nr 4-5, s. 519-537Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for diphoton events with large missing transverse momentum has been performed using 1.07 fb^-1 of proton-proton collision data at sqrt(s) = 7 TeV recorded with the ATLAS detector. No excess of events was observed above the Standard Model prediction and 95% Confidence Level (CL) upper limits are set on the production cross section for new physics: sigma < (22-129) fb in the context of a generalised model of gauge-mediated supersymmetry breaking (GGM) with a bino-like lightest neutralino, sigma < (27-91) fb in the context of a minimal model of gauge-mediated supersymmetry breaking (SPS8) and (15-27) fb in the context of a specific model with one universal extra dimension (UED). A 95% CL lower limit of 805 GeV, for bino masses above 50 GeV, is set on the GGM gluino mass. Lower limits of 145 TeV and 1.23 TeV are set on the SPS8 breaking scale Lambda and on the UED compactification scale 1/R, respectively. These limits provide the most stringent tests of these models to date.

  • 73. Aad, Georges
    et al.
    Lafaye, Remi
    CNRS.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for new phenomena in final states with large jet multiplicities and missing transverse momentum using root s=7 TeV pp collisions with the ATLAS detector2011Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, nr 11, s. 099-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Results are presented of a search for any particle(s) decaying to six or more jets in association with missing transverse momentum. The search is performed using 1.34 fb(-1) of root s = 7TeV proton-proton collisions recorded by the ATLAS detector during 2011. Data-driven techniques are used to determine the backgrounds in kinematic regions that require at least six, seven or eight jets, well beyond the multiplicities required in previous analyses. No evidence is found for physics beyond the Standard Model. The results are interpreted in the context of a supersymmetry model (MSUGRA/CMSSM) where they extend previous constraints.

  • 74. Aad, Georges
    et al.
    Lafaye, Remi
    Univ Savoie.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zwalinski, L.
    et al.,
    Search for new physics in the dijet mass distribution using 1 fb(-1) of pp collision data at root s=7 TeV collected by the ATLAS detector2012Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 708, nr 1-2, s. 37-54Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Invariant mass distributions of jet pairs (dijets) produced in LHC proton-proton collisions at a centre-of-mass energy root s = 7 TeV have been studied using a data set corresponding to an integrated luminosity of 1.0 fb(-1) recorded in 2011 by ATLAS. Dijet masses up to similar to 4 TeV are observed in the data, and no evidence of resonance production over background is found. Limits are set at 95% C.L. for several new physics hypotheses: excited quarks are excluded for masses below 299 TeV, axigluons are excluded for masses below 3.32 TeV. and colour octet scalar resonances are excluded for masses below 1.92 TeV.

  • 75. Aad, Georges
    et al.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    Univ Savoie, Annecy Le Vieux, France.
    Zwalinski, L.
    et, al.
    Measurement of the top quark pair production cross section in pp collisions at sqrt(s) = 7 TeV in dilepton final states with ATLAS2012Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 707, nr 5, s. 459-477Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A measurement of the production cross section of top quark pairs (t (t) over bar) in proton-proton collisions at a center-of-mass energy of 7 TeV recorded with the ATLAS detector at the Large Hadron Collider is reported. Candidate events are selected in the dilepton topology with large missing transverse energy and at least two jets. Using a data sample corresponding to an integrated luminosity of 35 pb(-1), a t (t) over bar production cross section sigma(t (t) over bar) = 177 +/- 20(stat.) +/- 14(syst.) +/- 7(lum.) pb is measured for an assumed top quark mass of m(t) = 172.5 GeV. A second measurement requiring at least one jet identified as coming from a b quark yields a comparable result, demonstrating that the dilepton final states are consistent with being accompanied by b-quark jets. These measurements are in good agreement with Standard Model predictions.

  • 76. Aad, Georges
    et al.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    Duke Univ, Dept Phys, Durham, NC 27706 USA.
    Zwalinski, L.
    et al.,
    Measurements of the electron and muon inclusive cross-sections in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector2012Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 707, nr 5, s. 438-458Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This Letter presents measurements of the differential cross-sections for inclusive electron and muonproduction in proton–proton collisions at a centre-of-mass energy of√s = 7 TeV, using data collectedby the ATLAS detector at the LHC. The muon cross-section is measured as a function of pT in the range4 < pT < 100 GeV and within pseudorapidity |η| < 2.5. In addition the electron and muon cross-sectionsare measured in the range 7 < pT < 26 GeV and within |η| < 2.0, excluding 1.37 < |η| < 1.52. Integratedluminosities of 1.3 pb−1and 1.4 pb−1are used for the electron and muon measurements, respectively.After subtraction of the W/Z/γ∗contribution, the differential cross-sections are found to be in goodagreement with theoretical predictions for heavy-flavour production obtained from Fixed Order NLOcalculations with NLL high-pT resummation, and to be sensitive to the effects of NLL resummation.

  • 77. Aad, Georges
    et al.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    Univ Savoie, Annecy Le Vieux, France.
    Zwalinski, L.
    et, al.
    Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS2012Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 707, nr 5, s. 478-496Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the results of a search for new, heavy particles that decay at a significant distance from theirproduction point into a final state containing charged hadrons in association with a high-momentummuon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV andan integrated luminosity of 33 pb−1collected in 2010 by the ATLAS detector operating at the LargeHadron Collider. Production of such particles is expected in various scenarios of physics beyond thestandard model. We observe no signal and place limits on the production cross-section of supersymmetricparticles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presentedfor different squark and neutralino masses, enabling extension of the limits to a variety of other models.

  • 78. Aad, Georges
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al.
    Jet energy measurement with the ATLAS detector in proton- proton collisions at sqrt(s) = 7 TeV2011Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    The jet energy scale (JES) and its systematic uncertainty are determined for jets measured with the ATLAS detector at the LHC in proton-proton collision data at a centre-of-mass energy of sqrt(s) = 7 TeV corresponding to an integrated luminosity of 38 inverse pb. Jets are reconstructed with the anti-kt algorithm with distance parameters R=0.4 or R=0.6. Jet energy and angle corrections are determined from Monte Carlo simulations to calibrate jets with transverse momenta pt > 20 GeV and pseudorapidities eta<4.5. The JES systematic uncertainty is estimated using the single isolated hadron response measured in situ and in test-beams. The JES uncertainty is less than 2.5% in the central calorimeter region (eta<0.8) for jets with 60 < pt < 800 GeV, and is maximally 14% for pt < 30 GeV in the most forward region 3.2<eta<4.5. The uncertainty for additional energy from multiple proton-proton collisions in the same bunch crossing is less than 1.5% per additional collision for jets with pt > 50 GeV after a dedicated correction for this effect. The JES is validated for jet transverse momenta up to 1 TeV to the level of a few percent using several in situ techniques by comparing a well-known reference such as the recoiling photon pt, the sum of the transverse momenta of tracks associated to the jet, or a system of low-pt jets recoiling against a high-pt jet. More sophisticated jet calibration schemes are presented based on calorimeter cell energy density weighting or hadronic properties of jets, providing an improved jet energy resolution and a reduced flavour dependence of the jet response. The JES systematic uncertainty determined from a combination of in situ techniques are consistent with the one derived from single hadron response measurements over a wide kinematic range. The nominal corrections and uncertainties are derived for isolated jets in an inclusive sample of high-pt jets.

  • 79. Aad, Georges
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al.
    Ks0 and Λ production in pp interactions at √s=0.9 and 7 TeV measured with the ATLAS detector at the LHC2012Inngår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. D85Artikkel i tidsskrift (Fagfellevurdert)
  • 80. Aad, Georges
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al.
    Measurement of inclusive jet and dijet production in pp collisions at sqrt(s) = 7 TeV using the ATLAS detector2011Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Inclusive jet and dijet cross sections have been measured in proton-proton collisions at a centre-of-mass energy of 7 TeV using the ATLAS detector at the Large Hadron Collider. The cross sections were measured using jets clustered with the anti-kT algorithm with parameters R=0.4 and R=0.6. These measurements are based on the 2010 data sample, consisting of a total integrated luminosity of 37 inverse picobarns. Inclusive jet double-differential cross sections are presented as a function of jet transverse momentum, in bins of jet rapidity. Dijet double-differential cross sections are studied as a function of the dijet invariant mass, in bins of half the rapidity separation of the two leading jets. The measurements are performed in the jet rapidity range |y|<4.4, covering jet transverse momenta from 20 GeV to 1.5 TeV and dijet invariant masses from 70 GeV to 5 TeV. The data are compared to expectations based on next-to-leading order QCD calculations corrected for non-perturbative effects, as well as to next-to-leading order Monte Carlo predictions. In addition to a test of the theory in a new kinematic regime, the data also provide sensitivity to parton distribution functions in a region where they are currently not well-constrained.

  • 81. Aad, Georges
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al.
    Measurement of the cross-section for b-jets produced in association with a Z boson at sqrt(s)=7 TeV with the ATLAS detector2012Manuskript (preprint) (Annet vitenskapelig)
  • 82. Aad, Georges
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al.
    Measurement of the inclusive W+- and Z/gamma cross sections in the electron and muon decay channels in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector2011Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    The production cross sections of the inclusive Drell-Yan processes W to l nu and Z/gamma to ll (l=e,mu) are measured in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector. The cross sections are reported integrated over a fiducial kinematic range, extrapolated to the full range and also evaluated differentially as a function of the W decay lepton pseudorapidity and the Z boson rapidity, respectively. Based on an integrated luminosity of about 35 pb^-1 collected in 2010, the precision of these measurements reaches a few per cent. The integrated and the differential W+- and Z/gamma cross sections in the e and mu channels are combined, and compared with perturbative QCD calculations, based on a number of different parton distribution sets available at NNLO.

  • 83. Aad, Georges
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    et, al.
    Measurement of the W -> lnu and Z/gamma* -> ll production cross sections in proton-proton collisions at sqrt(s) = 7 TeV with the ATLAS detector2010Inngår i: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, Vol. 12, s. 1-64Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    First measurements of the W -> lv and Z/gamma* -> ll (l = e; mu) production cross sections in proton-proton collisions at root s = 7 TeV are presented using data recorded by the ATLAS experiment at the LHC. The results are based on 2250 W -> lv and 179 Z/gamma* -> ll candidate events selected from a data set corresponding to an integrated luminosity of approximately 320 nb(-1). The measured total W and Z/gamma*-boson production cross sections times the respective leptonic branching ratios for the combined electron and muon channels are sigma(tot)(W) center dot BR(W -> lv) = 9.96 +/- 0.23(stat) +/- 0.50(syst) +/- 1.10(lumi) nb and sigma(tot)(Z) center dot BR(Z/gamma* -> ll) = 0.82 +/- 0.06 (stat) +/- 0.05 (syst) +/- 0.09 (lumi) nb (within the invariant mass window 66 < m(ll) < 116 GeV). The W/Z cross-section ratio is measured to be 11.7 +/- 0.9(stat) +/- 0.4(syst). In addition, measurements of the W+ and W- production cross sections and of the lepton charge asymmetry are reported. Theoretical predictions based on NNLO QCD calculations are found to agree with the measurements.

  • 84. Aad, Georges
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al.
    Measurement of the W to tau nu Cross Section in pp Collisions at sqrt(s) = 7 TeV with the ATLAS experiment2012Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. B706, s. 276-294Artikkel i tidsskrift (Fagfellevurdert)
  • 85. Aad, Georges
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al.
    Measurement of the WW cross section in sqrt(s) = 7 TeV pp collisions with ATLAS2011Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 107Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    This Letter presents a measurement of the W+W− production cross section in s√ = 7 TeV pp collisions by the ATLAS experiment, using 34 pb−1 of integrated luminosity produced by the Large Hadron Collider at CERN. Selecting events with two isolated leptons, each either an electron or a muon, 8 candidate events are observed with an expected background of 1.7±0.6 events. The measured cross section is 41+20−16(stat)±5(syst)±1(lumi) pb, which is consistent with the standard model prediction of 44±3 pb calculated at next-to-leading order in QCD.

  • 86. Aad, Georges
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al.
    Rapidity gap cross sections measured with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV2012Artikkel i tidsskrift (Fagfellevurdert)
  • 87. Aad, Georges
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al.
    Search for a heavy Standard Model Higgs boson in the channel H->ZZ->l(+)l(-)q(q)over-bar using the ATLAS detector2012Inngår i: Physical Letters B, ISSN 0370-2693, Vol. 707, nr 1, s. 27-45Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

     A search for a heavy Standard Model Higgs boson decaying via H -> ZZ -> l(+)l(-)q (q) over bar, where l = e, mu, is presented. The search is performed using a data set of pp collisions at root s = 7 TeV, corresponding to an integrated luminosity of 1.04 fb(-1) collected in 2011 by the ATLAS detector at the CERN LHC collider. No significant excess of events above the estimated background is found. Upper limits at 95% confidence level on the production cross section (relative to that expected from the Standard Model) of a Higgs boson with a mass in the range between 200 and 600 GeV are derived. Within this mass range, there is at present insufficient sensitivity to exclude a Standard Model Higgs boson. For a Higgs boson with a mass of 360 GeV, where the sensitivity is maximal, the observed and expected cross section upper limits are factors of 1.7 and 2.7, respectively, larger than the Standard Model prediction.

  • 88. Aad, Georges
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al.
    Search for dilepton resonances in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector2011Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 107, nr 27Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This Letter reports on a search for narrow high-mass resonances decaying into dilepton final states. The data were recorded by the ATLAS experiment in pp collisions at root s = 7 TeV at the Large Hadron Collider and correspond to a total integrated luminosity of 1.08 (1.21) fb(-1) in the e(+)e(-) (mu(+)mu(-)) channel. No statistically significant excess above the standard model expectation is observed and upper limits are set at the 95% C. L. on the cross section times branching fraction of Z' resonances and Randall-Sundrum gravitons decaying into dileptons as a function of the resonance mass. A lower mass limit of 1.83 TeV on the sequential standard model Z' boson is set. A Randall-Sundrum graviton with coupling k/(M) over bar Pl = 0.1 is excluded at 95% C. L. for masses below 1.63 TeV.

  • 89. Aad, Georges
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al.
    Search for New Phenomena in t(t)overbar Events with Large Missing Transverse Momentum in Proton-Proton Collisions at root s = 7 TeV with the ATLAS Detector2012Inngår i: Physical Review Letters, ISSN 0031-9007, Vol. 108, nr 4, s. 041805-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for new phenomena in t (t) over bar events with large missing transverse momentum in proton-proton collisions at a center-of-mass energy of 7 TeV is presented. The measurement is based on 1: 04 fb(-1) of data collected with the ATLAS detector at the LHC. Contributions to this final state may arise from a number of standard model extensions. The results are interpreted in terms of a model where new top-quark partners are pair produced and each decay to an on-shell top (or antitop) quark and a long-lived undetected neutral particle. The data are found to be consistent with standard model expectations. A limit at 95% confidence level is set excluding a cross section times branching ratio of 1.1 pb for a top-partner mass of 420 GeVand a neutral particle mass less than 10 GeV. In a model of exotic fourth generation quarks, toppartner masses are excluded up to 420 GeV and neutral particle masses up to 140 GeV.

  • 90. Aad, Georges
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al.
    Search for production of resonant states in the photon-jet mass distribution using pp collisions at sqrt(s) = 7 TeV collected by the ATLAS detector2011Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    This Letter describes a model-independent search for production of new resonant states in photon-jet events in 2.11 fb^-1 of proton-proton collisions at sqrt(s) = 7 TeV. We compare the photon-jet mass distribution to a data-driven background estimate and find consistency with the background hypothesis. Given the lack of evidence for a signal, we set 95% CL limits on generic Gaussian-shape signals and on a benchmark excited-quark (q*) model, excluding 2 TeV Gaussian resonances with cross section times branching ratio times acceptance times efficiency near 5 fb and excluding q* masses below 2.46 TeV, respectively.

  • 91. Aad, Georges
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al.
    Search for supersymmetry in final states with jets, missing transverse momentum and one isolated lepton in sqrts = 7 TeV pp collisions using 1 fb-1 of ATLAS data2012Inngår i: Phys. Rev., Vol. D85Artikkel i tidsskrift (Fagfellevurdert)
  • 92. Aad, Georges
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    et, al.
    Study of jets produced in association with a W boson in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector2012Inngår i: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 85, nr 9, s. 092002-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report a study of final states containing a W boson and hadronic jets, produced in proton-proton collisions at a center-of-mass energy of 7 TeV. The data were collected with the ATLAS detector at the CERN LHC and comprise the full 2010 data sample of 36 pb^-1. Cross sections are determined using both the electron and muon decay modes of the W boson and are presented as a function of inclusive jet multiplicity, N_jet, for up to five jets. At each multiplicity, cross sections are presented as a function of jet transverse momentum, the scalar sum of the transverse momenta of the charged lepton, missing transverse momentum, and all jets, the invariant mass spectra of jets, and the rapidity distributions of various combinations of leptons and final-state jets. The results, corrected for all detector effects and for all backgrounds such as diboson and top quark pair production, are compared with particle-level predictions from perturbative QCD. Leading-order multiparton event generators, normalized to the NNLO total cross section for inclusive W-boson production, describe the data reasonably well for all measured inclusive jet multiplicities. Next-to-leading-order calculations from MCFM, studied here for N_jet >= 2, and BlackHat-Sherpa, studied here for N_jet >= 4, are found to be mostly in good agreement with the data.

  • 93. Aad, Georges
    et al.
    Strandberg, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Rémi
    CNRS, IN2P3, LAPP, Annecy Le Vieux, France.
    et al.,
    Search for new phenomena with the monojet and missing transverse momentum signature using the ATLAS detector in sqrt(s) = 7 TeV proton-proton collisions2011Inngår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 705, nr 4, s. 294-312Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A search for new phenomena in events featuring a high energy jet and large missing transverse momentum in proton-proton collisions at root s = 7 TeV is presented using a dataset corresponding to an integrated luminosity of 33 pb(-1) recorded with the ATLAS detector at the Large Hadron Collider. The number of observed events is consistent with the Standard Model prediction. This result is interpreted in terms of limits on a model of Large Extra Dimensions.

  • 94. Abat, E.
    et al.
    Abdallah, J. M.
    Addy, T. N.
    Adragna, P.
    Aharrouche, M.
    Ahmad, A.
    Akesson, T. P. A.
    Aleksa, M.
    Alexa, C.
    Anderson, K.
    Andreazza, A.
    Anghinolfi, F.
    Antonaki, A.
    Arabidze, G.
    Arik, E.
    Atkinson, T.
    Baines, J.
    Baker, O. K.
    Banfi, D.
    Baron, S.
    Barr, A. J.
    Beccherle, R.
    Beck, H. P.
    Belhorma, B.
    Bell, P. J.
    Benchekroun, D.
    Benjamin, D. P.
    Benslama, K.
    Kuutmann, E. Bergeaas
    Bernabeu, J.
    Bertelsen, H.
    Binet, S.
    Biscarat, C.
    Boldea, V.
    Bondarenko, V. G.
    Boonekamp, M.
    Bosman, M.
    Bourdarios, C.
    Broklova, Z.
    Chromek, D. Burckhart
    Bychkov, V.
    Callahan, J.
    Calvet, D.
    Canneri, M.
    Garrido, M. Capeans
    Caprini, M.
    Sas, L. Cardiel
    Carli, T.
    Carminati, L.
    Carvalho, J.
    Cascella, M.
    Castillo, M. V.
    Catinaccio, A.
    Cauz, D.
    Cavalli, D.
    Cavalli Sforza, M.
    Cavasinni, V.
    Cetin, S. A.
    Chen, H.
    Cherkaoui, R.
    Chevalier, L.
    Chevallier, F.
    Chouridou, S.
    Ciobotaru, M.
    Citterio, M.
    Clark, A.
    Cleland, B.
    Cobal, M.
    Cogneras, E.
    Conde Muino, P.
    Consonni, M.
    Constantinescu, S.
    Cornelissen, T.
    Correard, S.
    Radu, A. Corso
    Costa, G.
    Costa, M. J.
    Costanzo, D.
    Cuneo, S.
    Cwetanski, P.
    Da Silva, D.
    Dam, M.
    Dameri, M.
    Danielsson, H. O.
    Dannheim, D.
    Darbo, G.
    Davidek, T.
    De, K.
    Defay, P. O.
    Dekhissi, B.
    Del Peso, J.
    Del Prete, T.
    Delmastro, M.
    Derue, F.
    Di Ciaccio, L.
    Di Girolamo, B.
    Dita, S.
    Dittus, F.
    Djama, F.
    Djobava, T.
    Dobos, D.
    Dobson, M.
    Dolgoshein, B. A.
    Dotti, A.
    Drake, G.
    Drasal, Z.
    Dressnandt, N.
    Driouchi, C.
    Drohan, J.
    Ebenstein, W. L.
    Eerola, P.
    Efthymiopoulos, I.
    Egorov, K.
    Eifert, T. F.
    Einsweiler, K.
    El Kacimi, M.
    Elsing, M.
    Emelyanov, D.
    Escobar, C.
    Etienvre, A. I.
    Fabich, A.
    Facius, K.
    Fakhr-Edine, A. I.
    Fanti, M.
    Farbin, A.
    Farthouat, P.
    Fassouliotis, D.
    Fayard, L.
    Febbraro, R.
    Fedin, O. L.
    Fenyuk, A.
    Fergusson, D.
    Ferrari, P.
    Ferrari, R.
    Ferreira, B. C.
    Ferrer, A.
    Ferrere, D.
    Filippini, G.
    Flick, T.
    Fournier, D.
    Francavilla, P.
    Francis, D.
    Froeschl, R.
    Froidevaux, D.
    Fullana, E.
    Gadomski, S.
    Gagliardi, G.
    Gagnon, P.
    Gallas, M.
    Gallop, B. J.
    Gameiro, S.
    Gan, K. K.
    Garcia, R.
    Garcia, C.
    Gavrilenko, I. L.
    Gemme, C.
    Gerlach, P.
    Ghodbane, N.
    Giakoumopoulou, V.
    Giangiobbe, V.
    Giokaris, N.
    Glonti, G.
    Goettfert, T.
    Golling, T.
    Gollub, N.
    Gomes, A.
    Gomez, M. D.
    Gonzalez-Sevilla, S.
    Goodrick, M. J.
    Gorfine, G.
    Gorini, B.
    Goujdami, D.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Grenier, P.
    Grigalashvili, N.
    Grishkevich, Y.
    Grosse-Knetter, J.
    Gruwe, M.
    Guicheney, C.
    Gupta, A.
    Haeberli, C.
    Haertel, R.
    Hajduk, Z.
    Hakobyan, H.
    Hance, M.
    Hansen, J. D.
    Hansen, P. H.
    Hara, K.
    Harvey, A., Jr.
    Hawkings, R. J.
    Heinemann, F. E. W.
    Correia, A. Henriques
    Henss, T.
    Hervas, L.
    Higon, E.
    Hill, J. C.
    Hoffman, J.
    Hostachy, J. Y.
    Hruska, I.
    Hubaut, F.
    Huegging, F.
    Hulsbergen, W.
    Hurwitz, M.
    Iconomidou-Fayard, L.
    Jansen, E.
    Plante, I. Jen-La
    Johansson, P. D. C.
    Jon-And, K.
    Joos, M.
    Jorgensen, S.
    Joseph, J.
    Kaczmarska, A.
    Kado, M.
    Karyukhin, A.
    Kataoka, M.
    Kayumov, F.
    Kazarov, A.
    Keener, P. T.
    Kekelidze, G. D.
    Kerschen, N.
    Kersten, S.
    Khomich, A.
    Khoriauli, G.
    Khramov, E.
    Khristachev, A.
    Khubua, J.
    Kittelmann, T. H.
    Klingenberg, R.
    Klinkby, E. B.
    Kodys, P.
    Koffas, T.
    Kolos, S.
    Konovalov, S. P.
    Konstantinidis, N.
    Kopikov, S.
    Korolkov, I.
    Kostyukhin, V.
    Kovalenko, S.
    Kowalski, T. Z.
    Krueger, K.
    Kramarenko, V.
    Kudin, L. G.
    Kulchitsky, Y.
    Lacasta, C.
    Lafaye, R.
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    Laforge, B.
    Lampl, W.
    Lanni, F.
    Laplace, S.
    Lari, T.
    Le Bihan, A-C
    Lechowski, M.
    Ledroit-Guillon, F.
    Lehmann, G.
    Leitner, R.
    Lelas, D.
    Lester, C. G.
    Liang, Z.
    Lichard, P.
    Liebig, W.
    Lipniacka, A.
    Lokajicek, M.
    Louchard, L.
    Lourerio, K. F.
    Lucotte, A.
    Luehring, F.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lundberg, B.
    Ma, H.
    Mackeprang, R.
    Maio, A.
    Maleev, V. P.
    Malek, F.
    Mandelli, L.
    Maneira, J.
    Mangin-Brinet, M.
    Manousakis, A.
    Mapelli, L.
    Marques, C.
    Marti i Garcia, S.
    Martin, F.
    Mathes, M.
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    McFarlane, K. W.
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    Mchedlidze, G.
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    Meroni, C.
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    Milstead, D.
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    Mitsou, V. A.
    Moed, S.
    Monnier, E.
    Moorhead, G.
    Morettini, P.
    Morozov, S. V.
    Mosidze, M.
    Mouraviev, S. V.
    Moyse, E. W. J.
    Munar, A.
    Myagkov, A.
    Nadtochi, A. V.
    Nakamura, K.
    Nechaeva, P.
    Negri, A.
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    Nessi, M.
    Nesterov, S. Y.
    Newcomer, F. M.
    Nikitine, I.
    Nikolaev, K.
    Nikolic-Audit, I.
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    Oh, S. H.
    Oleshko, S. B.
    Olszowska, J.
    Onofre, A.
    Aranda, C. Padilla
    Paganis, S.
    Pallin, D.
    Pantea, D.
    Paolone, V.
    Parodi, F.
    Parsons, J.
    Parzhitskiy, S.
    Pasqualucci, E.
    Passmored, S. M.
    Pater, J.
    Patrichev, S.
    Peez, M.
    Reale, V. Perez
    Perini, L.
    Peshekhonov, V. D.
    Petersen, J.
    Petersen, T. C.
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    Phillips, P. W.
    Pina, J.
    Pinto, B.
    Podlyski, F.
    Poggioli, L.
    Poppleton, A.
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    Pralavorio, P.
    Pribyl, L.
    Price, M. J.
    Prieur, D.
    Puigdengoles, C.
    Puzo, P.
    Rohne, O.
    Ragusa, F.
    Rajagopalan, S.
    Reeves, K.
    Reisinger, I.
    Rembser, C.
    de Renstrom, P. A. Bruckman
    Reznicek, P.
    Ridel, M.
    Risso, P.
    Riu, I.
    Robinson, D.
    Roda, C.
    Roe, S.
    Romaniouk, A.
    Rousseau, D.
    Rozanov, A.
    Ruiz, A.
    Rusakovich, N.
    Rust, D.
    Ryabov, Y. F.
    Ryjov, V.
    Salto, O.
    Salvachua, B.
    Salzburger, A.
    Sandaker, H.
    Rios, C. Santamarina
    Santi, L.
    Santoni, C.
    Saraiva, J. G.
    Sarri, F.
    Sauvage, G.
    Says, L. P.
    Schaefer, M.
    Schegelsky, V. A.
    Schiavi, C.
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    Schlager, G.
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    Schwemling, P.
    Schwindling, J.
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    Seliverstov, D. M.
    Serin, L.
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    Sloper, J. E.
    Smirnov, S. Yu.
    Smirnova, L.
    Solans, C.
    Solodkov, A.
    Solovianov, O.
    Soloviev, I.
    Sosnovtsev, V. V.
    Spano, F.
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    Starchenko, E.
    Straessner, A.
    Suchkov, S. I.
    Suk, M.
    Szczygiel, R.
    Tarrade, F.
    Tartarelli, F.
    Tas, P.
    Tayalati, Y.
    Tegenfeldt, F.
    Teuscher, R.
    Thioye, M.
    Tikhomirov, V. O.
    Timmermans, C. J. W. P.
    Tisserant, S.
    Toczek, B.
    Tremblet, L.
    Troncon, C.
    Tsiareshka, P.
    Tyndel, M.
    Unel, M. Karagoez
    Unal, G.
    Unel, G.
    Usai, G.
    Van Berg, R.
    Valero, A.
    Valkar, S.
    Valls, J. A.
    Vandelli, W.
    Vannucci, F.
    Vartapetian, A.
    Vassilakopoulos, V. I.
    Vasilyeva, L.
    Vazeille, F.
    Vernocchi, F.
    Vetter-Cole, Y.
    Vichou, I.
    Vinogradov, V.
    Virzi, J.
    Vivarelli, I.
    de Vivie, J. B.
    Volpi, M.
    Anh, T. Vu
    Wang, C.
    Warren, M.
    Weber, J.
    Weber, M.
    Weidberg, A. R.
    Weingarten, J.
    Wells, P. S.
    Werner, P.
    Wheeler, S.
    Wiessmann, M.
    Wilkens, H.
    Williams, H. H.
    Wingerter-Seez, I.
    Yasu, Y.
    Zaitsev, A.
    Zenin, A.
    Zenis, T.
    Zenonos, Z.
    Zhang, H.
    Zhelezko, A.
    Zhou, N.
    Combined performance studies for electrons at the 2004 ATLAS combined test-beam2010Inngår i: Journal of Instrumentation, ISSN 1748-0221, Vol. 5, s. P11006-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In 2004 at the ATLAS (A Toroidal LHC ApparatuS) combined test beam, one slice of the ATLAS barrel detector (including an Inner Detector set-up and the Liquid Argon calorimeter) was exposed to particles from the H8 SPS beam line at CERN. It was the first occasion to test the combined electron performance of ATLAS. This paper presents results obtained for the momentum measurement p with the Inner Detector and for the performance of the electron measurement with the LAr calorimeter (energy E linearity and resolution) in the presence of a magnetic field in the Inner Detector for momenta ranging from 20 GeV/c to 100 GeV/c. Furthermore the particle identification capabilities of the Transition Radiation Tracker, Bremsstrahlungs-recovery algorithms relying on the LAr calorimeter and results obtained for the E/p ratio and a way how to extract scale parameters will be discussed.

  • 95. Abat, E.
    et al.
    Abdallah, J. M.
    Addy, T. N.
    Adragna, P.
    Aharrouche, M.
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    A Layer Correlation technique for pion energy calibration at the 2004 ATLAS Combined Beam Test2011Inngår i: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 6, s. 06001-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new method for calibrating the hadron response of a segmented calorimeter is developed and successfully applied to beam test data. It is based on a principal component analysis of energy deposits in the calorimeter layers, exploiting longitudinal shower development information to improve the measured energy resolution. Corrections for invisible hadronic energy and energy lost in dead material in front of and between the calorimeters of the ATLAS experiment were calculated with simulated Geant4 Monte Carlo events and used to reconstruct the energy of pions impinging on the calorimeters during the 2004 Barrel Combined Beam Test at the CERN H8 area. For pion beams with energies between 20 GeV and 180 GeV, the particle energy is reconstructed within 3% and the energy resolution is improved by between 11% and 25% compared to the resolution at the electromagnetic scale.

  • 96. Abat, E.
    et al.
    Abdallah, J. M.
    Egorov, K.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zhou, N.
    Grahn, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    et, al
    Study of the response of the ATLAS central calorimeter to pions of energies from 3 to 9 GeV2009Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 607, nr 2, s. 372-386Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A fully instrumented slice of the ATLAS central detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. in this paper, the response of the central calorimeters to pions with energies in the range between 3 and 9 GeV is presented. The linearity and the resolution of the combined calorimetry (electromagnetic and hadronic calorimeters) was measured and compared to the prediction of a detector simulation program using the toolkit Geant 4.

  • 97. Abat, E.
    et al.
    Grahan, Karl-Johan
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lafaye, Remi
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Zhou, N.
    et, al
    Photon reconstruction in the ATLAS Inner Detector and Liquid Argon Barrel Calorimeter at the 2004 Combined Test Beam2011Inngår i: Journal of Instrumentation, ISSN 1748-0221, Vol. 6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The reconstruction of photons in the ATLAS detector is studied with data taken during the 2004 Combined Test Beam, where a full slice of the ATLAS detector was exposed to beams of particles of known energy at the CERN SPS. The results presented show significant differences in the longitudinal development of the electromagnetic shower between converted and unconverted photons as well as in the total measured energy. The potential to use the reconstructed converted photons as a means to precisely map the material of the tracker in front of the electromagnetic calorimeter is also considered. All results obtained are compared with a detailed Monte-Carlo simulation of the test-beam setup which is based on the same simulation and reconstruction tools as those used for the ATLAS detector itself.

  • 98. Abata, E.
    et al.
    Abdallah, J. M.
    Addy, T. N.
    Adragna, P.
    Aharrouche, M.
    Ahmad, A.
    Akesson, T. P. A.
    Aleksa, M.
    Alexa, C.
    Anderson, K.
    Anghinolfi, F.
    Antonaki, A.
    Arabidze, G.
    Arik, E.
    Baker, O. K.
    Banfi, D.
    Baron, S.
    Beck, H. P.
    Belhorma, B.
    Benchekroun, D.
    Benjamin, D. P.
    Benslama, K.
    Kuutmann, E. Bergeaas
    Bertelsen, H.
    Binet, S.
    Biscarat, C.
    Boldea, V.
    Bondarenko, V. G.
    Boonekamp, M.
    Bosman, M.
    Bourdarios, C.
    Chromek, D. Burckhart
    Bychkov, V.
    Callahan, J.
    Calvet, D.
    Canneri, M.
    Garrido, M. Capeans
    Caprini, M.
    Sas, L. Cardiel
    Carli, T.
    Carminati, L.
    Carvalho, J.
    Cascella, M.
    Castillo, M. V.
    Catinaccio, A.
    Sforza, M. Cavalli
    Cavalli, D.
    Cavasinni, V.
    Cetin, S. A.
    Chen, H.
    Cherkaoui, R.
    Chevallier, F.
    Ciobotaru, M.
    Citterio, M.
    Cleland, B.
    Cogneras, E.
    Muino, P. Conde
    Consonni, M.
    Constantinescu, S.
    Cornelissen, T.
    Radu, A. Corso
    Costa, G.
    Cwetanski, P.
    Da Silva, D.
    DAM, M.
    Danielsson, H. O.
    Dannheim, D.
    Davidek, T.
    De, K.
    Defay, P. O.
    Dekhissi, B.
    Del Peso, J.
    Delmastro, M.
    Del Prete, T.
    Derue, F.
    Di Ciaccio, L.
    Di Girolamo, B.
    Dita, S.
    Dittus, F.
    Djama, F.
    Djobava, T.
    Dobson, M.
    Dolgoshein, B. A.
    Dotti, A.
    Drake, G.
    Dressnandt, N.
    Driouchi, C.
    Ebenstein, W. L.
    Eerola, P.
    Efthymiopoulos, I.
    Egorov, K.
    Eifert, T. F.
    El Kacimi, M.
    Etienvre, A. I.
    Fabich, A.
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    Fanti, M.
    Farbin, A.
    Farthouat, P.
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    Fayard, L.
    Febbraro, R.
    Fedin, O. L.
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    Ferrari, R.
    Ferreira, B. C.
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    Fournier, D.
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    Comes, A.
    Gomez, M. D.
    Gonzalez, V.
    Gorini, B.
    Goujdamiav, D.
    Grahn, K. J.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Grenier, P.
    Grigalashvili, N.
    Grishkevich, Y.
    Gruwe, M.
    Guicheney, C.
    Gupta, A.
    Haeberli, C.
    Hajduk, Z.
    Hakobyan, H.
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    Hervas, L.
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    Hubaut, F.
    Hulsbergen, W.
    Hurwitz, M.
    Iconomidou-Fayard, L.
    Jen-La Plante, I.
    Johansson, P. D. C.
    Jon-And, K.
    Joos, M.
    Jorgensen, S.
    Kaczmarska, A.
    Kado, M.
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    Kataoka, M.
    Kayumov, F.
    Kazarov, A.
    Keener, P. T.
    Kekelidze, G. D.
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    Khubua, J.
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    Koffas, T.
    Kolos, S.
    Konovalov, S. P.
    Kopikov, S.
    Korolkov, I.
    Kovalenko, S.
    Kowalski, T. Z.
    Kruger, K.
    Kramarenko, V.
    Kudin, L. G.
    Kulchitsky, Y.
    Lafaye, R.
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    Laforge, B.
    Lampl, W.
    Lanni, F.
    Laplace, S.
    Le Bihan, A. C.
    Lechowski, M.
    Ledroit-Guillon, F.
    Lehmann, G.
    Leitner, R.
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    Liang, Z.
    Lichard, P.
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    Louchard, L.
    Loureiro, K.
    Lucotte, A.
    Luehring, F.
    Lundberg, B.
    Lund-Jensen, Bengt
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
    Ma, H.
    Mackeprang, R.
    Maio, A.
    Maleev, V. P.
    Malek, F.
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    Tartarelli, F.
    Tas, P.
    Tayalati, Y.
    Teuscher, R.
    Thioye, M.
    Tikhomirov, V. O.
    Tisserant, S.
    Torres, J.
    Tremblet, L.
    Tsiareshka, P.
    Tsiskaridze, V.
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    Unel, G.
    Usai, G.
    Valero, A.
    Valkar, S.
    Valls, J. A.
    Van Berg, R.
    Vandelli, W.
    Vannucci, F.
    Vartapetian, A.
    Vassilakopoulos, V. I.
    Vassilieva, L.
    Vazeille, F.
    Vetter-Cole, Y.
    Vichou, I.
    Vinogradov, V.
    Vivarelli, I.
    Volpi, M.
    Wang, C.
    Werner, P.
    Wheeler, S.
    Wiesmann, M.
    Wilkens, H.
    Williams, H. H.
    Wingerter-Seez, I.
    Yasu, Y.
    Zaitsev, A.
    Zenin, A.
    Zenis, T.
    Zenonos, Z.
    Zhang, H.
    Zhou, N.
    Study of energy response and resolution of the ATLAS barrel calorimeter to hadrons of energies from 20 to 350 GeV2010Inngår i: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 621, nr 1-3, s. 134-150Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A fully instrumented slice of the ATLAS detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. In this paper, the results of the measurements of the response of the barrel calorimeter to hadrons with energies in the range 20-350 GeV and beam impact points and angles corresponding to pseudo-rapidity values in the range 0.2-0.65 are reported. The results are compared to the predictions of a simulation program using the Geant 4 toolkit. (C) 2010 Published by Elsevier B.V.

  • 99. Abreu, H.
    et al.
    Aharrouche, M.
    Aleksa, M.
    Aperio Bella, L.
    Archambault, J. P.
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France .
    al., et
    Performance of the electronic readout of the ATLAS liquid argon calorimeters2010Inngår i: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 5Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ATLAS detector has been designed for operation at the Large Hadron Collider at CERN. ATLAS includes electromagnetic and hadronic liquid argon calorimeters, with almost 200,000 channels of data that must be sampled at the LHC bunch crossing frequency of 40 MHz. The calorimeter electronics calibration and readout are performed by custom electronics developed specifically for these purposes. This paper describes the system performance of the ATLAS liquid argon calibration and readout electronics, including noise, energy and time resolution, and long term stability, with data taken mainly from full-system calibration runs performed after installation of the system in the ATLASdetector hall at CERN.

  • 100. Adam, Claire
    et al.
    Kneur, Jean-Loic
    Lafaye, Remi
    Université Savoie, France.
    Plehn, Tilman
    Rauch, Michael
    Zerwas, Dirk
    Measuring Unification2011Inngår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 71, nr 1, s. 1-19Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    If supersymmetry is observed at the LHC its model parameters can be measured at the electroweak scale. We discuss the expected precision on the parameter determination, including a proper treatment of experimental and theoretical errors. Particular attention is paid to degenerate solutions. Using the SFitter framework we perform a bottom-up reconstruction of the unified parameters at the high scale, including a full error propagation.

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