SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "LAR1:uu ;pers:(Aad G);srt2:(2010-2014)"

Sökning: LAR1:uu > Aad G > (2010-2014)

Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
21.
  • Aad, G., et al. (författare)
  • Determination of the Strange-Quark Density of the Proton from ATLAS Measurements of the W -> lv and Z -> ll Cross Sections
  • 2012
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 109:1, s. 012001
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>AQCD analysis is reported of ATLAS data on inclusive W-+/- and Z boson production in pp collisions at the LHC, jointly with ep deep-inelastic scattering data from HERA. The ATLAS data exhibit sensitivity to the light quark sea composition and magnitude at Bjorken x similar to 0:01. Specifically, the data support the hypothesis of a symmetric composition of the light quark sea at low x. The ratio of the strange-to-down sea quark distributions is determined to be 1:00(-0:28)(+0.25) at absolute four-momentum transfer squared Q(2) = 1: 9 GeV2 and x = 0: 023.</p>
  •  
22.
  • Aad, G., et al. (författare)
  • Drift Time Measurement in the ATLAS Liquid Argon Electromagnetic Calorimeter using Cosmic Muons
  • 2010
  • Ingår i: European Physical Journal C. - 1434-6044 .- 1434-6052. ; 70:3, s. 755-785
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The ionization signals in the liquid argon of the ATLAS electromagnetic calorimeter are studied in detail using cosmic muons. In particular, the drift time of the ionization electrons is measured and used to assess the intrinsic uniformity of the calorimeter gaps and estimate its impact on the constant term of the energy resolution. The drift times of electrons in the cells of the second layer of the calorimeter are uniform at the level of 1.3% in the barrel and 2.8% in the endcaps. This leads to an estimated contribution to the constant term of (0.29(-0.04)(+0.05))% in the barrel and (0.54(-0.04)(+0.06))% in the endcaps. The same data are used to measure the drift velocity of ionization electrons in liquid argon, which is found to be 4.61 +/- 0.07 mm/mu s at 88.5 K and 1 kV/mm.</p>
  •  
23.
  • Aad, G., et al. (författare)
  • Dynamics of isolated-photon plus jet production in pp collisions at root s=7 TeV with the ATLAS detector
  • 2013
  • Ingår i: Nuclear Physics B. - 0550-3213 .- 1873-1562. ; 875:3, s. 483-535
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>The dynamics of isolated-photon plus jet production in pp collisions at a centre-of-mass energy of 7 TeV has been studied with the ATLAS detector at the LHC using an integrated luminosity of 37 pb(-1). Measurements of isolated-photon plus jet bin-averaged cross sections are presented as functions of photon transverse energy, jet transverse momentum and jet rapidity. In addition, the bin-averaged cross sections as functions of the difference between the azimuthal angles of the photon and the jet, the photon jet invariant mass and the scattering angle in the photon jet centre-of-mass frame have been measured. Next-to-leading-order QCD calculations are compared to the measurements and provide a good description of the data, except for the case of the azimuthal opening angle.</p>
  •  
24.
  • Aad, G., et al. (författare)
  • Electron and photon energy calibration with the ATLAS detector using LHC Run 1 data
  • 2014
  • Ingår i: European Physical Journal C. - 1434-6044 .- 1434-6052. ; 74:10, s. 3071
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>This paper presents the electron and photon energy calibration achieved with the ATLAS detector using about 25 fb(-1) of LHC proton-proton collision data taken at centre-of-mass energies of root s = 7 and 8 TeV. The reconstruction of electron and photon energies is optimised using multivariate algorithms. The response of the calorimeter layers is equalised in data and simulation, and the longitudinal profile of the electromagnetic showers is exploited to estimate the passive material in front of the calorimeter and reoptimise the detector simulation. After all corrections, the Z resonance is used to set the absolute energy scale. For electrons from Z decays, the achieved calibration is typically accurate to 0.05% in most of the detector acceptance, rising to 0.2% in regions with large amounts of passive material. The remaining inaccuracy is less than 0.2-1% for electrons with a transverse energy of 10 GeV, and is on average 0.3% for photons. The detector resolution is determined with a relative inaccuracy of less than 10% for electrons and photons up to 60 GeV transverse energy, rising to 40% for transverse energies above 500 GeV.</p>
  •  
25.
  • Aad, G., et al. (författare)
  • Electron performance measurements with the ATLAS detector using the 2010 LHC proton-proton collision data
  • 2012
  • Ingår i: European Physical Journal C. - 1434-6044 .- 1434-6052. ; 72:3, s. 1909
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>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.</p>
  •  
26.
  • Aad, G., et al. (författare)
  • Electron reconstruction and identification efficiency measurements with the ATLAS detector using the 2011 LHC proton-proton collision data
  • 2014
  • Ingår i: European Physical Journal C. - 1434-6044 .- 1434-6052. ; 74:7, s. UNSP 2941
  • Tidskriftsartikel (refereegranskat)abstract
    • <p> Many of the interesting physics processes to be measured at the LHC have a signature involving one or more isolated electrons. The electron reconstruction and identification efficiencies of the ATLAS detector at the LHC have been evaluated using proton-proton collision data collected in 2011 at TeV and corresponding to an integrated luminosity of 4.7 fb. Tag-and-probe methods using events with leptonic decays of and bosons and mesons are employed to benchmark these performance parameters. The combination of all measurements results in identification efficiencies determined with an accuracy at the few per mil level for electron transverse energy greater than 30 GeV.</p>
  •  
27.
  • Aad, G., et al. (författare)
  • Evidence for Electroweak Production of W(+/-)W(+/-)jj in pp Collisions at root s=8 TeV with the ATLAS Detector
  • 2014
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 113:14, s. 141803
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>This Letter presents the first study of WWjj, same-electric-charge diboson production in associationwith two jets, using 20.3 fb−1 of proton-proton collision data at ffiffiffis p ¼ 8 TeV recorded by the ATLASdetector at the Large Hadron Collider. Events with two reconstructed same-charge leptons (ee, eμ,and μμ) and two or more jets are analyzed. Production cross sections are measured in two fiducialregions, with different sensitivities to the electroweak and strong production mechanisms. First evidencefor WWjj production and electroweak-only WWjj production is observed with a significance of 4.5and 3.6 standard deviations, respectively. The measured production cross sections are in agreement withstandard model predictions. Limits at 95% confidence level are set on anomalous quartic gauge couplings.</p>
  •  
28.
  • Aad, G., et al. (författare)
  • Evidence for the associated production of a W boson and a top quark in ATLAS at root s=7 TeV
  • 2012
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 716:1, s. 142-159
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>This Letter presents evidence for the associated production of a W boson and a top quark using 2.05 fb(-1) of pp collision data at root s = 7 TeV accumulated with the ATLAS detector at the LHC. The analysis is based on the selection of the dileptonic final states with events featuring two isolated leptons, electron or muon, with significant transverse missing momentum and at least one jet. An approach based on boosted decision trees has been developed to improve the discrimination of single top-quark Wt events from background. A template fit to the final classifier distributions is performed to determine the cross-section. The result is incompatible with the background-only hypothesis at the 3.3 sigma level, the expected sensitivity assuming the Standard Model production rate being 3.4 sigma. The corresponding cross-section is determined and found to be sigma(wt) = 16.8 +/- 2.9 (stat) +/- 4.9 (syst) pb, in good agreement with the Standard Model expectation. From this result the CKM matrix element vertical bar V-tb vertical bar = 1.03(-0.19)(+0.16) is derived assuming that the Wt production through vertical bar V-ts vertical bar and vertical bar V-td vertical bar is small.</p>
  •  
29.
  • Aad, G., et al. (författare)
  • Evidence for the spin-0 nature of the Higgs boson using ATLAS data
  • 2013
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 726:1-3, s. 120-144
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Studies of the spin and parity quantum numbers of the Higgs boson are presented, based on protonproton collision data collected by the ATLAS experiment at the LHC. The Standard Model spin-parity J(P) = 0(+) hypothesis is compared with alternative hypotheses using the Higgs boson decays H -&gt; gamma gamma, H -&gt; ZZ* -&gt; 4l and H -&gt; WW* -&gt; l nu l nu, as well as the combination of these channels. The analysed dataset corresponds to an integrated luminosity of 20.7 fb(-1) collected at a centre-of-mass energy of root s = 8 TeV. For the H -&gt; ZZ* -&gt; 4l decay mode the dataset corresponding to an integrated luminosity of 4.6 fb(-1) collected at root s = 7 TeV is included. The data are compatible with the Standard Model J(P) = 0+ quantum numbers for the Higgs boson, whereas all alternative hypotheses studied in this Letter, namely some specific J(P) = 0(-), 1(+), 1(-), 2(+) models, are excluded at confidence levels above 97.8%. This exclusion holds independently of the assumptions on the coupling strengths to the Standard Model particles and in the case of the J(P) = 2(+) model, of the relative fractions of gluon-fusion and quark-antiquark production of the spin-2 particle. The data thus provide evidence for the spin-0 nature of the Higgs boson, with positive parity being strongly preferred.</p>
  •  
30.
  • Aad, G., et al. (författare)
  • Fiducial and differential cross sections of Higgs boson production measured in the four-lepton decay channel in pp collisions at root s=8 TeV with the ATLAS detector
  • 2014
  • Ingår i: Physics Letters B. - 0370-2693 .- 1873-2445. ; 738, s. 234-253
  • Tidskriftsartikel (refereegranskat)abstract
    • <p>Measurements of fiducial and differential cross sections of Higgs boson production in the H -&gt; ZZ* -&gt; 4l decay channel are presented. The cross sections are determined within a fiducial phase space and corrected for detection efficiency and resolution effects. They are based on 20.3 fb(-1) of pp collision data, produced at root s= 8 TeV centre-of-mass energy at the LHC and recorded by the ATLAS detector. The differential measurements are performed in bins of transverse momentum and rapidity of the four-lepton system, the invariant mass of the subleading lepton pair and the decay angle of the leading lepton pair with respect to the beam line in the four-lepton rest frame, as well as the number of jets and the transverse momentum of the leading jet. The measured cross sections are compared to selected theoretical calculations of the Standard Model expectations. No significant deviation from any of the tested predictions is found.</p>
  •  
Skapa referenser, mejla, bekava och länka
 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy