Change search
Refine search result
123 1 - 50 of 121
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Aad, G
    et al.
    Abat, E
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    Univ Michigan, Dept Phys, Randall Lab.
    zur Nedden, M
    Zutshi, V
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    et, al
    Charged-particle multiplicities in pp interactions at root s=900 GeV measured with the ATLAS detector at the LHC ATLAS Collaboration2010In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 688, no 1, p. 21-42Article in journal (Refereed)
  • 2. Aad, G
    et al.
    Abbot, B
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics.
    Strandberg, Jonas
    Univ Michigan, Dept Phys.
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    Zwalinski, L
    et, al
    Observation of a Centrality-Dependent Dijet Asymmetry in Lead-Lead Collisions at root s(NN)=2.76 TeV with the ATLAS Detector at the LHC2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 105, no 25, p. 252303-Article in journal (Refereed)
    Abstract [en]

    By using the ATLAS detector, observations have been made of a centrality-dependent dijet asymmetry in the collisions of lead ions at the Large Hadron Collider. In a sample of lead-lead events with a per-nucleon center of mass energy of 2.76 TeV, selected with a minimum bias trigger, jets are reconstructed in fine-grained, longitudinally segmented electromagnetic and hadronic calorimeters. The transverse energies of dijets in opposite hemispheres are observed to become systematically more unbalanced with increasing event centrality leading to a large number of events which contain highly asymmetric dijets. This is the first observation of an enhancement of events with such large dijet asymmetries, not observed in proton-proton collisions, which may point to an interpretation in terms of strong jet energy loss in a hot, dense medium.

  • 3. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    Univ Michigan, Dept Phys, Randall Lab.
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    et, al
    Search for New Particles in Two-Jet Final States in 7 TeV Proton-Proton Collisions with the ATLAS Detector at the LHC2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 105, no 16, p. 161801-Article in journal (Refereed)
    Abstract [en]

    A search for new heavy particles manifested as resonances in two-jet final states is presented. The data were produced in 7 TeV proton-proton collisions by the LHC and correspond to an integrated luminosity of 315 nb(-1) collected by the ATLAS detector. No resonances were observed. Upper limits were set on the product of cross section and signal acceptance for excited-quark (q*) production as a function of q* mass. These exclude at the 95% C. L. the q* mass interval 0: 30< m(q)*< 1:26 TeV, extending the reach of previous experiments.

  • 4. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    Univ Michigan, Dept Phys, Ann Arbor.
    Zutshi, V.
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    Performance of the ATLAS detector using first collision data2010In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 9, p. 056-Article in journal (Refereed)
    Abstract [en]

    More than half a million minimum-bias events of LHC collision data were collected by the ATLAS experiment in December 2009 at centre-of-mass energies of 0.9 TeV and 2.36 TeV. This paper reports on studies of the initial performance of the ATLAS detector from these data. Comparisons between data and Monte Carlo predictions are shown for distributions of several track- and calorimeter-based quantities. The good performance of the ATLAS detector in these first data gives confidence for successful running at higher energies.

  • 5. Aad, G
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    Univ Michigan, Dept Phys, Randall Lab.
    Zutshi, V
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    The ATLAS Simulation Infrastructure2010In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 70, no 3, p. 823-874Article in journal (Refereed)
    Abstract [en]

    The simulation software for the ATLAS Experiment at the Large Hadron Collider is being used for large-scale production of events on the LHC Computing Grid. This simulation requires many components, from the generators that simulate particle collisions, through packages simulating the response of the various detectors and triggers. All of these components come together under the ATLAS simulation infrastructure. In this paper, that infrastructure is discussed, including that supporting the detector description, interfacing the event generation, and combining the GEANT4 simulation of the response of the individual detectors. Also described are the tools allowing the software validation, performance testing, and the validation of the simulated output against known physics processes.

  • 6. Aad, G
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    Univ Michigan, Dept Phys, Ann Arbor.
    Zutshi, V
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    et, al
    Drift Time Measurement in the ATLAS Liquid Argon Electromagnetic Calorimeter using Cosmic Muons2010In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 70, no 3, p. 755-785Article in journal (Refereed)
    Abstract [en]

    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.

  • 7. Aad, G
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    Univ Michigan, Randall Lab .
    Zutshi, V
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    et, al
    Readiness of the ATLAS liquid argon calorimeter for LHC collisions2010In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 70, no 3, p. 723-753Article in journal (Refereed)
    Abstract [en]

    The ATLAS liquid argon calorimeter has been operating continuously since August 2006. At this time, only part of the calorimeter was readout, but since the beginning of 2008, all calorimeter cells have been connected to the ATLAS readout system in preparation for LHC collisions. This paper gives an overview of the liquid argon calorimeter performance measured in situ with random triggers, calibration data, cosmic muons, and LHC beam splash events. Results on the detector operation, timing performance, electronics noise, and gain stability are presented. High energy deposits from radiative cosmic muons and beam splash events allow to check the intrinsic constant term of the energy resolution. The uniformity of the electromagnetic barrel calorimeter response along eta (averaged over phi) is measured at the percent level using minimum ionizing cosmic muons. Finally, studies of electromagnetic showers from radiative muons have been used to cross-check the Monte Carlo simulation. The performance results obtained using the ATLAS readout, data acquisition, and reconstruction software indicate that the liquid argon calorimeter is well-prepared for collisions at the dawn of the LHC era.

  • 8. Aad, G
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    Univ Michigan, Dept Phys.
    Zutshi, V
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    et, al
    Readiness of the ATLAS Tile Calorimeter for LHC collisions2010In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 70, no 4, p. 1193-1236Article in journal (Refereed)
    Abstract [en]

    The Tile hadronic calorimeter of the ATLAS detector has undergone extensive testing in the experimental hall since its installation in late 2005. The readout, control and calibration systems have been fully operational since 2007 and the detector has successfully collected data from the LHC single beams in 2008 and first collisions in 2009. This paper gives an overview of the Tile Calorimeter performance as measured using random triggers, calibration data, data from cosmic ray muons and single beam data. The detector operation status, noise characteristics and performance of the calibration systems are presented, as well as the validation of the timing and energy calibration carried out with minimum ionising cosmic ray muons data. The calibration systems' precision is well below the design value of 1%. The determination of the global energy scale was performed with an uncertainty of 4%.

  • 9. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    Univ Michigan, Dept Phys.
    Zutshi, V.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Search for quark contact interactions in dijet angular distributions in pp collisions at root s=7 TeV measured with the ATLAS detector2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 694, no 4/5, p. 327-345Article in journal (Refereed)
    Abstract [en]

    Dijet angular distributions from the first LHC pp collisions at center-of-mass energy root s = 7 TeV have been measured with the ATLAS detector. The dataset used for this analysis represents an integrated luminosity of 3.1 pb(-1). Dijet chi distributions and centrality ratios have been measured up to dijet masses of 2.8 TeV, and found to be in good agreement with Standard Model predictions. Analysis of the chi distributions excludes quark contact interactions with a compositeness scale Lambda below 3.4 TeV, at 95% confidence level, significantly exceeding previous limits.

  • 10. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    Univ Michigan, Dept Phys.
    Zutshi, V.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Studies of the performance of the ATLAS detector using cosmic-ray muons2011In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 71, no 3, p. 1593-Article in journal (Refereed)
  • 11. Aad, G
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    Univ Michigan, Dept Phys, Randall Lab.
    Zutshi, V
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    et, al
    The ATLAS Inner Detector commissioning and calibration2010In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 70, no 3, p. 787-821Article in journal (Refereed)
    Abstract [en]

    The ATLAS Inner Detector is a composite tracking system consisting of silicon pixels, silicon strips and straw tubes in a 2 T magnetic field. Its installation was completed in August 2008 and the detector took part in data-taking with single LHC beams and cosmic rays. The initial detector operation, hardware commissioning and in-situ calibrations are described. Tracking performance has been measured with 7.6 million cosmic-ray events, collected using a tracking trigger and reconstructed with modular pattern-recognition and fitting software. The intrinsic hit efficiency and tracking trigger efficiencies are close to 100%. Lorentz angle measurements for both electrons and holes, specific energy-loss calibration and transition radiation turn-on measurements have been performed. Different alignment techniques have been used to reconstruct the detector geometry. After the initial alignment, a transverse impact parameter resolution of 22.1 +/- 0.9 mu m and a relative momentum resolution sigma (p) /p=(4.83 +/- 0.16)x10(-4) GeV(-1)xp (T) have been measured for high momentum tracks.

  • 12. Aad, G
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    Univ Michigan, Dept Phys, Randall Lab .
    Zutshia, V
    Lafaye, Remi
    Univ Savoie, LAPP, CNTS IN2P3, Annecy Le Vieux, France.
    et, al
    Commissioning of the ATLAS Muon Spectrometer with cosmic rays2010In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 70, no 3, p. 875-916Article in journal (Refereed)
    Abstract [en]

    The ATLAS detector at the Large Hadron Collider has collected several hundred million cosmic ray events during 2008 and 2009. These data were used to commission the Muon Spectrometer and to study the performance of the trigger and tracking chambers, their alignment, the detector control system, the data acquisition and the analysis programs. We present the performance in the relevant parameters that determine the quality of the muon measurement. We discuss the single element efficiency, resolution and noise rates, the calibration method of the detector response and of the alignment system, the track reconstruction efficiency and the momentum measurement. The results show that the detector is close to the design performance and that the Muon Spectrometer is ready to detect muons produced in high energy proton-proton collisions.

  • 13. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Measurement of the upsilon(1S) production cross-section in pp collisions at root s=7 TeV in ATLAS ATLAS Collaboration2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 705, no 1-2, p. 9-27Article in journal (Refereed)
    Abstract [en]

    A measurement of the cross-section for upsilon(1S) -> mu(+)mu(-) production in proton-proton collisions at centre of mass energy of 7 TeV is presented. The cross-section is measured as a function of the upsilon(1S) transverse momentum in two bins of rapidity, vertical bar y(upsilon(1S))vertical bar < 1.2 and 1.2 < vertical bar y(upsilon(1S))vertical bar < 2.4. The measurement requires that both muons have transverse momentum p(T)(mu) > 4 GeV and pseuclorapidity vertical bar eta(mu)vertical bar < 2.5 in order to reduce theoretical uncertainties on the acceptance, which depend on the poorly known polarisation. The results are based on an integrated luminosity of 1.13 pb(-1), collected with the ATLAS detector at the Large Hadron Collider. The cross-section measurement is compared to theoretical predictions: it agrees to within a factor of two with a prediction based on the NRQCD model including colour-singlet and colour-octet matrix elements as implemented in PYTHIA while it disagrees by up to a factor of ten with the next-to-leading order prediction based on the colour-singlet model.

  • 14. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Search for Diphoton Events with Large Missing Transverse Energy in 7 TeV Proton-Proton Collisions with the ATLAS Detector2011In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 106, no 12, p. 121803-Article in journal (Refereed)
    Abstract [en]

    A search for diphoton events with large missing transverse energy is presented. The data were collected with the ATLAS detector in proton-proton collisions at root s = 7 TeV at the CERN Large Hadron Collider and correspond to an integrated luminosity of 3: 1 pb(-1). No excess of such events is observed above the standard model background prediction. In the context of a specific model with one universal extra dimension with compactification radius R and gravity-induced decays, values of 1/R < 729 GeV are excluded at 95% C. L., providing the most sensitive limit on this model to date.

  • 15. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    A search for new physics in dijet mass and angular distributions in pp collisions at root s=7 TeV measured with the ATLAS detector2011In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 13, p. 053044-Article in journal (Refereed)
    Abstract [en]

    A search for new interactions and resonances produced in LHC proton-proton (pp) collisions at a centre-of-mass energy root s = 7 TeV was performed with the ATLAS detector. Using a dataset with an integrated luminosity of 36 pb(-1), dijet mass and angular distributions were measured up to dijet masses of similar to 3.5 TeV and were found to be in good agreement with Standard Model predictions. This analysis sets limits at 95% CL on various models for new physics: an excited quark is excluded for mass between 0.60 and 2.64 TeV, an axigluon hypothesis is excluded for axigluon masses between 0.60 and 2.10 TeV and quantum black holes are excluded in models with six extra space-time dimensions for quantum gravity scales between 0.75 and 3.67 TeV. Production cross section limits as a function of dijet mass are set using a simplified Gaussian signal model to facilitate comparisons with other hypotheses. Analysis of the dijet angular distribution using a novel technique simultaneously employing the dijet mass excludes quark contact interactions with a compositeness scale 3 below 9.5 TeV.

  • 16. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Charged-particle multiplicities in pp interactions measured with the ATLAS detector at the LHC2011In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 13, p. 053033-Article in journal (Refereed)
    Abstract [en]

    Measurements are presented from proton-proton collisions at centre-of-mass energies of root s = 0.9, 2.36 and 7 TeV recorded with the ATLAS detector at the LHC. Events were collected using a single-arm minimum-bias trigger. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the relationship between the mean transverse momentum and charged-particle multiplicity are measured. Measurements in different regions of phase space are shown, providing diffraction-reduced measurements as well as more inclusive ones. The observed distributions are corrected to well-defined phase-space regions, using model-independent corrections. The results are compared to each other and to various Monte Carlo (MC) models, including a new AMBT1 pythia6 tune. In all the kinematic regions considered, the particle multiplicities are higher than predicted by the MC models. The central charged-particle multiplicity per event and unit of pseudorapidity, for tracks with p(T) > 100 MeV, is measured to be 3.483 +/- 0.009 (stat) +/- 0.106 (syst) at root s = 0.9 TeV and 5.630 +/- 0.003 (stat) +/- 0.169 (syst) at root s = 7 TeV.

  • 17. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Limits on the production of the standard model Higgs boson in pp collisions at root s=7 TeV with the ATLAS detector2011In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 71, no 9, p. 1728-Article in journal (Refereed)
    Abstract [en]

    A search for the Standard Model Higgs boson at the Large Hadron Collider (LHC) running at a centre-of-mass energy of 7 TeV is reported, based on a total integrated luminosity of up to 40 pb(-1) collected by the ATLAS detector in 2010. Several Higgs boson decay channels: H -> gamma gamma, H -> ZZ(()*()) -> llll, H -> ZZ -> LL nu nu, H -> ZZ -> llqq, H -> WW(()*()) -> l nu l nu and H -> WW -> l nu qq (l is e, mu) are combined in a mass range from 110 GeV to 600 GeV. The highest sensitivity is achieved in the mass range between 160 GeV and 170 GeV, where the expected 95% CL exclusion sensitivity is at Higgs boson production cross sections 2.3 times the Standard Model prediction. Upper limits on the cross section for its production are determined. Models with a fourth generation of heavy leptons and quarks with Standard Model-like couplings to the Higgs boson are also investigated and are excluded at 95% CL for a Higgs boson mass in the range from 140 GeV to 185 GeV.

  • 18. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Luminosity determination in pp collisions at root s=7 TeV using the ATLAS detector at the LHC2011In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 71, no 4, p. 1630-Article in journal (Refereed)
    Abstract [en]

    Measurements of luminosity obtained using the ATLAS detector during early running of the Large Hadron Collider (LHC) at root s = 7 TeV are presented. The luminosity is independently determined using several detectors and multiple algorithms, each having different acceptances, systematic uncertainties and sensitivity to background. The ratios of the luminosities obtained from these methods are monitored as a function of time and of mu, the average number of inelastic interactions per bunch crossing. Residual time- and mu-dependence between the methods is less than 2% for 0 < mu < 2.5. Absolute luminosity calibrations, performed using beam separation scans, have a common systematic uncertainty of +/- 11%, dominated by the measurement of the LHC beam currents. After calibration, the luminosities obtained from the different methods differ by at most +/- 2%. The visible cross sections measured using the beam scans are compared to predictions obtained with the PYTHIA and PHOJET event generators and the ATLAS detector simulation.

  • 19. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al.
    Measurement of Dijet Azimuthal Decorrelations in pp Collisions at root s=7 TeV2011In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 106, no 17, p. 172002-Article in journal (Refereed)
    Abstract [en]

    Azimuthal decorrelations between the two central jets with the largest transverse momenta are sensitive to the dynamics of events with multiple jets. We present a measurement of the normalized differential cross section based on the full data set ( integral Ldt = 36 pb(-1)) acquired by the ATLAS detector during the 2010 root s = 7 TeV proton-proton run of the LHC. The measured distributions include jets with transverse momenta up to 1.3 TeV, probing perturbative QCD in a high-energy regime.

  • 20. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Measurement of dijet production with a veto on additional central jet activity in pp collisions at root s=7 TeV using the ATLAS detector2011In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 9, p. 053-Article in journal (Refereed)
    Abstract [en]

    A measurement of jet activity in the rapidity interval bounded by a dijet system is presented. Events are vetoed if a jet with transverse momentum greater than 20 GeV is found between the two boundary jets. The fraction of dijet events that survive the jet veto is presented for boundary jets that are separated by up to six units of rapidity and with mean transverse momentum 50 < <(p)over bar>T < 500 GeV. The mean multiplicity of jets above the veto scale in the rapidity interval bounded by the dijet system is also presented as an alternative method for quantifying perturbative QCD emission. The data are compared to a next-to-leading order plus parton shower prediction from the POWHEG-BOX, an all-order resummation using the HEJ calculation and the PYTHIA, HERWIG++ and ALPGEN event generators. The measurement was performed using pp collisions at root s = 7 TeV using data recorded by the ATLAS detector in 2010.

  • 21. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Measurement of multi-jet cross sections in proton-proton collisions at a 7 TeV center-of-mass energy2011In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 71, no 11, p. 1763-Article in journal (Refereed)
    Abstract [en]

     Inclusive multi-jet production is studied in proton-proton collisions at a center-of-mass energy of 7 TeV, using the ATLAS detector. The data sample corresponds to an integrated luminosity of 2.4 pb(-1). Results on multi-jet cross sections are presented and compared to both leading-order plus parton-shower Monte Carlo predictions and to next-to-leading-order QCD calculations.

  • 22. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Measurement of the centrality dependence of J/psi yields and observation of Z production in lead-lead collisions with the ATLAS detector at the LHC2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 697, no 4, p. 294-312Article in journal (Refereed)
    Abstract [en]

    Using the ATLAS detector, a centrality-dependent suppression has been observed in the yield of J/psi mesons produced in the collisions of lead ions at the Large Hadron Collider. In a sample of minimum-bias lead-lead collisions at a nucleon-nucleon centre of mass energy root s(NN) = 2.76 TeV, corresponding to an integrated luminosity of about 6.7 mu b(-1), J/psi mesons are reconstructed via their decays to mu(+)mu(-) pairs. The measured J/psi yield, normalized to the number of binary nucleon-nucleon collisions, is found to significantly decrease from peripheral to central collisions. The centrality dependence is found to be qualitatively similar to the trends observed at previous, lower energy experiments. The same sample is used to reconstruct Z bosons in the mu(+)mu(-) final state, and a total of 38 candidates are selected in the mass window of 66 to 116 GeV. The relative Z yields as a function of centrality are also presented, although no conclusion can be inferred about their scaling with the number of binary collisions, because of limited statistics. This analysis provides the first results on J/psi and Z production in lead-lead collisions at the LHC.

  • 23. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Measurement of the differential cross-sections of inclusive, prompt and non-prompt J/psi production in proton-proton collisions at root s=7 TeV2011In: Nuclear Physics B, ISSN 0550-3213, E-ISSN 1873-1562, Vol. 850, no 3, p. 387-444Article in journal (Refereed)
    Abstract [en]

    The inclusive J/psi production cross-section and fraction of J/psi mesons produced in B-hadron decays are measured in proton proton collisions at root s = 7 TeV with the ATLAS detector at the LHC, as a function of the transverse momentum and rapidity of the J/psi, using 2.3 pb(-1) of integrated luminosity. The cross-section is measured from a minimum P(T) of 1 GeV to a maximum of 70 GeV and for rapidities within vertical bar y vertical bar < 2.4 giving the widest reach of any measurement of J/psi production to date. The differential production cross-sections of prompt and non-prompt J/psi are separately determined and are compared to Colour Singlet NNLO*, Colour Evaporation Model, and FONLL predictions.

  • 24. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Measurement of the inclusive isolated prompt photon cross-section in pp collisions at root s=7 TeV using 35 pb(-1) of ATLAS data2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 706, no 2-3, p. 150-167Article in journal (Refereed)
    Abstract [en]

    A measurement of the differential 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 vertical bar < 1.37 and 1.52 <= vertical bar eta vertical bar < 2.37 in the transverse energy range 45 <= E(T) < 400 GeV. The results are based on an integrated luminosity of 35 pb(-1), collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.

  • 25. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Measurement of the inelastic proton-proton cross-section at root s=7 TeV with the ATLAS detector2011In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 2, p. 463-Article in journal (Refereed)
    Abstract [en]

    The dependence of the rate of proton-proton interactions on the centre-of-mass collision energy, root s, is of fundamental importance for both hadron collider physics and particle astrophysics. The dependence cannot yet be calculated from first principles; therefore, experimental measurements are needed. Here we present the first measurement of the inelastic proton-proton interaction cross-section at a centre-of-mass energy, root s, of 7 TeV using the ATLAS detector at the Large Hadron Collider. Events are selected by requiring hits on scintillation counters mounted in the forward region of the detector. An inelastic crosssection of 60.3 +/- 2.1 mb is measured for xi > 5x10(-6), where xi is calculated from the invariant mass, M(X), of hadrons selected using the largest rapidity gap in the event. For diffractive events, this corresponds to requiring at least one of the dissociation masses to be larger than 15.7 GeV.

  • 26. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Measurement of the jet fragmentation function and transverse profile in proton-proton collisions at a center-of-mass energy of 7 TeV with the ATLAS detector2011In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 71, no 11, p. 1795-Article in journal (Refereed)
    Abstract [en]

     The jet fragmentation function and transverse profile for jets with 25 GeV < p(Tjet) < 500 GeV and |eta(jet)| < 1.2 produced in proton-proton collisions with a center-of-mass energy of 7 TeV are presented. The measurement is performed using data with an integrated luminosity of 36 pb(-1). Jets are reconstructed and their momentum measured using calorimetric information. The momenta of the charged particle constituents are measured using the tracking system. The distributions corrected for detector effects are compared with various Monte Carlo event generators and generator tunes. Several of these choices show good agreement with the measured fragmentation function. None of these choices reproduce both the transverse profile and fragmentation function over the full kinematic range of the measurement.  

  • 27. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Measurement of the production cross section for W-bosons in association with jets in pp collisions at root s=7 TeV with the ATLAS detector2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 698, no 5, p. 325-345Article in journal (Refereed)
    Abstract [en]

    This Letter reports on a first measurement of the inclusive W + jets cross section in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC, with the ATLAS detector. Cross sections, in both the electron and muon decay modes of the W-boson, are presented as a function of jet multiplicity and of the transverse momentum of the leading and next-to-leading jets in the event. Measurements are also presented of the ratio of cross sections sigma (W + >= n)/sigma(W + >= n - 1) for inclusive jet multiplicities n = 1-4. The results, based on an integrated luminosity of 1.3 pb(-1), have been corrected for all known detector effects and are quoted in a limited and well-defined range of jet and lepton kinematics. The measured cross sections are compared to particle-level predictions based on perturbative QCD. Next-to-leading order calculations, studied here for n <= 2, are found in good agreement with the data. Leading-order multiparton event generators, normalized to the NNLO total cross section, describe the data well for all measured jet multiplicities.

  • 28. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    Univ Michigan, Dept Phys, Ann Arbor.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Measurement of the top quark-pair production cross section with ATLAS in pp collisions at root s=7 TeV2011In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 71, no 3, p. 1577-Article in journal (Refereed)
    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 two different topologies: single lepton (electron e or muon mu) with large missing transverse energy and at least four jets, and dilepton (ee, mu mu or e mu) with large missing transverse energy and at least two jets. In a data sample of 2.9 pb(-1), 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding expected backgrounds from non-t (t) over bar Standard Model processes are estimated using data-driven methods and determined to be 12.2 +/- 3.9 events and 2.5 +/- 0.6 events, respectively. The kinematic properties of the selected events are consistent with SM t (t) over bar production. The inclusive top quark pair production cross-section is measured to besigma(t (t) over bar) = 145 +/- 31 (stat.)(-27)(+42) (syst.) pb.The measurement agrees with perturbative QCD calculations.

  • 29. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Measurement of the transverse momentum distribution of Z/gamma* bosons in proton-proton collisions at root s=7 TeV with the ATLAS detector2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 705, no 5, p. 415-434Article in journal (Refereed)
    Abstract [en]

    A measurement of the Z/gamma* transverse momentum (p(T)(Z)) distribution in proton-proton collisions at root s = 7 TeV is presented using Z/gamma* -> e(+)e(-) and Z/gamma* -> mu(+)mu(-) decays collected with the ATLAS detector in data sets with integrated luminosities of 35 pb(-1) and 40 pb(-1), respectively. The normalized differential cross sections are measured separately for electron and muon decay channels as well as for their combination up to pi of 350 GeV for invariant dilepton masses 66 GeV < m(ll) < 116 GeV. The measurement is compared to predictions of perturbative QCD and various event generators. The prediction of resummed QCD combined with fixed order perturbative QCD is found to be in good agreement with the data.

  • 30. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Measurement of the W charge asymmetry in the W -> mu nu decay mode in pp collisions at root s=7 TeV with the ATLAS detector2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 701, no 1, p. 31-49Article in journal (Refereed)
    Abstract [en]

    This Letter reports a measurement of the muon charge asymmetry from W bosons produced in proton-proton collisions at a centre-of-mass energy of 7 TeV with the ATLAS experiment at the LHC. The asymmetry is measured in the W -> mu nu decay mode as a function of the muon pseudorapidity using a data sample corresponding to a total integrated luminosity of 31 pb(-1). The results are compared to predictions based on next-to-leading order calculations with various parton distribution functions. This measurement provides information on the u and d quark momentum fractions in the proton.

  • 31. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Lafaye, Remi
    et al.,
    Measurement of the Z -> tau tau cross section with the ATLAS detector2011In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 84, no 11, p. 112006-Article in journal (Refereed)
    Abstract [en]

    The Z -> tau tau cross section is measured with the ATLAS experiment at the LHC in four different final states determined by the decay modes of the tau leptons: muon-hadron, electron-hadron, electron-muon, and muon-muon. The analysis is based on a data sample corresponding to an integrated luminosity of 36 pb(-1), at a proton-proton center-of-mass energy of root s = 7 TeV. Cross sections are measured separately for each final state in fiducial regions of high detector acceptance, as well as in the full phase space, over the mass region 66-116 GeV. The individual cross sections are combined and the product of the total Z production cross section and Z -> tau tau branching fraction is measured to be 0.97 +/- 0.07(stat) +/- 0.06(syst) +/- 0: 03(lumi) nb, in agreement with next-to-next-to-leading order calculations.

  • 32. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Measurement of underlying event characteristics using charged particles in pp collisions at root s = 900 GeV and 7 TeV with the ATLAS detector2011In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 83, no 11, p. 112001-Article in journal (Refereed)
    Abstract [en]

    Measurements of charged particle distributions, sensitive to the underlying event, have been performed with the ATLAS detector at the LHC. The measurements are based on data collected using a minimum-bias trigger to select proton-proton collisions at center-of-mass energies of 900 GeV and 7 TeV. The "underlying event'' is defined as those aspects of a hadronic interaction attributed not to the hard scattering process, but rather to the accompanying interactions of the rest of the proton. Three regions are defined in azimuthal angle with respect to the highest transverse momentum charged particle in the event, such that the region transverse to the dominant momentum-flow is most sensitive to the underlying event. In each of these regions, distributions of the charged particle multiplicity, transverse momentum density, and average p(T) are measured. The data show generally higher underlying event activity than that predicted by Monte Carlo models tuned to pre-LHC data.

  • 33. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Measurement of W gamma and Z gamma production in proton-proton collisions at root s=7 TeV with the ATLAS detector2011In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 9, p. 072-Article in journal (Refereed)
    Abstract [en]

    We present studies of W and Z bosons with associated high energy photons produced in pp collisions at root s = 7 TeV. The analysis uses 35 pb(-1) of data collected by the ATLAS experiment in 2010. The event selection requires W and Z bosons decaying into high pT leptons (electrons or muons) and a photon with E(T) > 15 GeV separated from the lepton(s) by a distance Delta R(l, gamma) > 0.7 in eta-phi space. A total of 95 (97) pp -> e(+/-)nu gamma + X (pp -> mu(+/-)nu gamma + X) and 25 (23) pp -> e(+)e(-)gamma + X (pp -> mu(+)mu(-)gamma + X) event candidates are selected. The kinematic distributions of the leptons and photons and the production cross sections are measured. The data are found to agree with Standard Model predictions that include next-to-leading-order O(alpha alpha(s)) contributions.

  • 34. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Measurements of underlying-event properties using neutral and charged particles in pp collisions at root s=900 GeV and root s=7 TeV with the ATLAS detector at the LHC2011In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 71, no 5, p. 1636-Article in journal (Refereed)
    Abstract [en]

    We present first measurements of charged and neutral particle-flow correlations in pp collisions using the ATLAS calorimeters. Data were collected in 2009 and 2010 at centre-of-mass energies of 900 GeV and 7 TeV. Events were selected using a minimum-bias trigger which required a charged particle in scintillation counters on either side of the interaction point. Particle flows, sensitive to the underlying event, are measured using clusters of energy in the ATLAS calorimeters, taking advantage of their fine granularity. No Monte Carlo generator used in this analysis can accurately describe the measurements. The results are independent of those based on charged particles measured by the ATLAS tracking systems and can be used to constrain the parameters of Monte Carlo generators.

  • 35. Aad, G.
    et al.
    Grahn, Karl-Johan
    Ist Nazl Fis Nucl, Lab Nazl Frascati, I-00044 Frascati, Italy .
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Search for a heavy gauge boson decaying to a charged lepton and a neutrino in 1 fb(-1) of pp collisions at root s=7 TeV using the ATLAS detector ATLAS Collaboration2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 705, no 1-2, p. 28-46Article in journal (Refereed)
    Abstract [en]

    The ATLAS detector at the LHC is used to search for high-mass states, such as heavy charged gauge bosons (W '), decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 1.04 fb(-1). No excess above Standard Model expectations is observed. A W ' with Sequential Standard Model couplings is excluded at the 95% confidence level for masses up to 2.15 TeV.

  • 36.
    Aad, G.
    et al.
    Univ Freiburg.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Search for contact interactions in dimuon events from pp collisions at root s=7 TeV with the ATLAS detector2011In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 84, no 1, p. 011101-Article in journal (Refereed)
    Abstract [en]

    A search for contact interactions has been performed using dimuon events recorded with the ATLAS detector in proton-proton collisions at root s = 7 TeV. The data sample corresponds to an integrated luminosity of 42 pb(-1). No significant deviation from the standard model is observed in the dimuon mass spectrum, allowing the following 95% C. L. limits to be set on the energy scale of contact interactions: Lambda > 4: 9 TeV (4.5 TeV) for constructive (destructive) interference in the left-left isoscalar compositeness model. These limits are the most stringent to date for mu mu qq contact interactions.

  • 37. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Search for diphoton events with large missing transverse energy with 36 pb(-1) of 7 TeV proton-proton collision data with the ATLAS detector2011In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 71, no 10, p. 1744-Article in journal (Refereed)
    Abstract [en]

    Making use of 36 pb(-1) of proton-proton collision data at root s = 7 TeV, the ATLAS Collaboration has performed a search for diphoton events with large missing transverse energy. Observing no excess of events above the Standard Model prediction, a 95% Confidence Level ( CL) upper limit is set on the cross section for new physics of sigma < 0.38-0.65 pb in the context of a generalised model of gauge-mediated supersymmetry breaking (GGM) with a bino-like lightest neutralino, and of sigma < 0.18-0.23 pb in the context of a specific model with one universal extra dimension (UED). A 95% CL lower limit of 560 GeV, for bino masses above 50 GeV, is set on the GGM gluino mass, while a lower limit of 1/R > 961 GeV is set on the UED compactification radius R. These limits provide the most stringent tests of these models to date.

  • 38. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Search for heavy long-lived charged particles with the ATLAS detector in pp collisions at root s=7 TeV2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 703, no 4, p. 428-446Article in journal (Refereed)
    Abstract [en]

    A search for long-lived charged particles reaching the muon spectrometer is performed using a data sample of 37 pb(-1) from pp collisions at root s = 7 TeV collected by the ATLAS detector at the LHC in 2010. No excess is observed above the estimated background. Stable (tau) over bar sleptons are excluded at 95% CL up to a mass of 136 GeV, in GMSB models with N(5) = 3 , m(messenger) = 250 TeV, sign(mu) = 1 and tan beta = 5. Electroweak production of sleptons is excluded up to a mass of 110 GeV. Gluino R-hadrons in a generic interaction model are excluded up to masses of 530 GeV to 544 GeV depending on the fraction of R-hadrons produced as (g) over bar -balls.

  • 39. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Search for high mass dilepton resonances in pp collisions at root s=7 TeV with the ATLAS experiment2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 700, no 3-4, p. 163-180Article in journal (Refereed)
    Abstract [en]

    This Letter presents a search for high mass e(+)e(-) or mu(+)mu(-) resonances in pp collisions at root s = 7 TeV at the LHC. The data were recorded by the ATLAS experiment during 2010 and correspond to a total integrated luminosity of similar to 40 pb(-1). No statistically significant excess above the Standard Model expectation is observed in the search region of dilepton invariant mass above 110 GeV. Upper limits at the 95% confidence level are set on the cross section times branching ratio of Z' resonances decaying to dielectrons and dimuons as a function of the resonance mass. A lower mass limit of 1.048 TeV on the Sequential Standard Model Z' boson is derived, as well as mass limits on Z* and E(6)-motivated Z' models.

  • 40. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Search for high-mass states with one lepton plus missing transverse momentum in proton-proton collisions root s=7 TeV with the ATLAS detector2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 701, no 1, p. 50-69Article in journal (Refereed)
    Abstract [en]

    The ATLAS detector is used to search for high-mass states, such as heavy charged gauge bosons (W'. W*), decaying to a charged lepton (electron or muon) and a neutrino. Results are presented based on the analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 36 pb(-1). No excess beyond standard model expectations is observed. A W' with sequential standard model couplings is excluded at 95% confidence level for masses below 1.49 TeV, and a W* (charged chiral boson) for masses below 1.35 TeV.

  • 41. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Search for massive long-lived highly ionising particles with the ATLAS detector at the LHC2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 698, no 5, p. 353-370Article in journal (Refereed)
    Abstract [en]

    A search is made for massive highly ionising particles with lifetimes in excess of 100 ns, with the ATLAS experiment at the Large Hadron Collider, using 3.1 pb(-1) of pp collision data taken at root s = 7 TeV. The signature of energy loss in the ATLAS inner detector and electromagnetic calorimeter is used. No such particles are found and limits on the production cross section for electric charges 6e <= vertical bar q vertical bar <= 17e and masses 200 GeV <= m <= 1000 GeV are set in the range 1-12 pb for different hypotheses on the production mechanism.

  • 42. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Search for neutral MSSM Higgs bosons decaying to tau(+)tau(-) pairs in proton-proton collisions root s=7 TeV with the ATLAS detector2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 705, no 3, p. 174-192Article in journal (Refereed)
    Abstract [en]

    A search for neutral Higgs bosons decaying to pairs of tau leptons with the ATLAS detector at the LHC is presented. The analysis is based on proton-proton collisions at a center-of-mass energy of 7 TeV, recorded in 2010 and corresponding to an integrated luminosity of 36 pb(-1). After signal selection, 276 events are observed in this data sample. The observed number of events is consistent with the total expected background of 269 +/- 36 events. Exclusion limits at the 95% confidence level are derived for the production cross section of a generic Higgs boson phi as a function of the Higgs boson mass and for A/H/h production in the Minimal Supersymmetric Standard Model (MSSM) as a function of the parameters m(A) and tan beta.

  • 43. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Search for pair production of first or second generation leptoquarks in proton-proton collisions at root s=7 TeV using the ATLAS detector at the LHC2011In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 83, no 11, p. 112006-Article in journal (Refereed)
    Abstract [en]

    This paper describes searches for the pair production of first or second generation scalar leptoquarks using 35 pb(-1) of proton-proton collision data recorded by the ATLAS detector at root s = 7 TeV. Leptoquarks are searched in events with two oppositely-charged muons or electrons and at least two jets, and in events with one muon or electron, missing transverse momentum and at least two jets. After event selection, the observed yields are consistent with the predicted backgrounds. Leptoquark production is excluded at the 95% CL for masses M-LQ < 376 (319) GeV and M-LQ < 422 (362) GeV for first and second generation scalar leptoquarks, respectively, when assuming the branching fraction of a leptoquark to a charged lepton is equal to 1.0 (0.5).

  • 44. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Search for squarks and gluinos using final states with jets and missing transverse momentum with the ATLAS detector in root s=7 TeV proton-proton collisions2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 701, no 2, p. 186-203Article in journal (Refereed)
    Abstract [en]

    A search for squarks and gluinos in final states containing jets, missing transverse momentum and no electrons or muons is presented. The data were recorded by the ATLAS experiment in root s = 7 TeV proton-proton collisions at the Large Hadron Collider. No excess above the Standard Model background expectation was observed in 35 pb(-1) of analysed data. Gluino masses below 500 GeV are excluded at the 95% confidence level in simplified models containing only squarks of the first two generations, a gluino octet and a massless neutralino. The exclusion increases to 870 GeV for equal mass squarks and gluinos. In MSUGRA/CMSSM models with tan beta = 3, A(0) = 0 and mu > 0, squarks and gluinos of equal mass are excluded below 775 GeV. These are the most stringent limits to date.

  • 45. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Search for stable hadronising squarks and gluinos with the ATLAS experiment at the LHC2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 701, no 1, p. 1-19Article in journal (Refereed)
    Abstract [en]

    Hitherto unobserved long-lived massive particles with electric and/or colour charge are predicted by a range of theories which extend the Standard Model. In this Letter a search is performed at the ATLAS experiment for slow-moving charged particles produced in proton-proton collisions at 7 TeV centre-of-mass energy at the LHC, using a data-set corresponding to an integrated luminosity of 34 pb(-1). No deviations from Standard Model expectations are found. This result is interpreted in a framework of supersymmetry models in which coloured sparticles can hadronise into long-lived bound hadronic states, termed R-hadrons, and 95% CL limits are set on the production cross-sections of squarks and gluinos. The influence of R-hadron interactions in matter was studied using a number of different models, and lower mass limits for stable sbottoms and stops are found to be 294 and 309 GeV respectively. The lower mass limit for a stable gluino lies in the range from 562 to 586 GeV depending on the model assumed. Each of these constraints is the most stringent to date.

  • 46. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Search for supersymmetric particles in events with lepton pairs and large missing transverse momentum in root s=7 TeV proton-proton collisions with the ATLAS experiment2011In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 71, no 7, p. 1682-Article in journal (Refereed)
    Abstract [en]

    Results are presented of searches for the production of supersymmetric particles decaying into final states with missing transverse momentum and exactly two isolated leptons in root s = 7 TeV proton-proton collisions at the Large Hadron Collider. Search strategies requiring lepton pairs with identical-sign or opposite-sign electric charges are described. In a data sample corresponding to an integrated luminosity of 35 pb(-1) collected with the ATLAS detector, no significant excesses are observed. Based on specific benchmark models, limits are placed on the squark mass between 450 and 690 GeV for squarks approximately degenerate in mass with gluinos, depending on the supersymmetric mass hierarchy considered.

  • 47. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Search for supersymmetry in pp collisions at root s=7 TeV in final states with missing transverse momentum and b-jets2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 701, no 4, p. 398-416Article in journal (Refereed)
    Abstract [en]

    Results are presented of a search for supersymmetric particles in events with large missing transverse momentum and at least one heavy flavour jet candidate in root s = 7 TeV proton proton collisions. In a data sample corresponding to an integrated luminosity of 35 pb(-1) recorded by the ATLAS experiment at the Large Hadron Collider, no significant excess is observed with respect to the prediction for Standard Model processes. For R-parity conserving models in which sbottoms (stops) are the only squarks to appear in the gluino decay cascade, gluino masses below 590 GeV (520 GeV) are excluded at the 95% C.L. The results are also interpreted in an MSUGRA/CMSSM supersymmetry breaking scenario with tan beta = 40 and in an SO(10) model framework.

  • 48. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Search for Supersymmetry Using Final States with One Lepton, Jets, and Missing Transverse Momentum with the ATLAS Detector in root s=7 TeV pp Collisions2011In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 106, no 13, p. 131802-1-131802-19Article in journal (Refereed)
    Abstract [en]

    This Letter presents the first search for supersymmetry in final states containing one isolated electron or muon, jets, and missing transverse momentum from root s = 7 TeV proton-proton collisions at the LHC. The data were recorded by the ATLAS experiment during 2010 and correspond to a total integrated luminosity of 35 pb(-1). No excess above the standard model background expectation is observed. Limits are set on the parameters of the minimal supergravity framework, extending previous limits. Within this framework, for A(0) = 0 GeV, tan beta = 3, and mu > 0 and for equal squark and gluino masses, gluino masses below 700 GeV are excluded at 95% confidence level.

  • 49. Aad, G.
    et al.
    Grahn, Karl-Johan
    DESY, D-2000 Hamburg, Germany .
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Search for the Standard Model Higgs boson in the decay channel H -> ZZ(()*()) -> 4l with the ATLAS detector2011In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 705, no 5, p. 435-451Article in journal (Refereed)
    Abstract [en]

    A search for the Standard Model Higgs boson in the decay channel H -> ZZ(()*()) l(+)l(-)l'l'(-), where l = e, mu, is presented. Proton-proton collision data at root s = 7 TeV recorded with the ATLAS detector and corresponding to an average integrated luminosity of 2.1 fb(-1) are compared to the Standard Model expectations. Upper limits on the production cross section of a Standard Model Higgs boson with a mass between 110 and 600 GeV are derived. The observed (expected) 95% confidence level upper limit on the production cross section for a Higgs boson with a mass of 194 GeV, the region with the best expected sensitivity for this search, is 0.99 (1.01) times the Standard Model prediction. The Standard Model Higgs boson is excluded at 95% confidence level in the mass ranges 191-197, 199-200 and 214-224 GeV.

  • 50. Aad, G.
    et al.
    Grahn, Karl-Johan
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    University of Chicago.
    Zwalinski, L.
    Lafaye, Remi
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et, al
    Study of jet shapes in inclusive jet production in pp collisions at root s=7 TeV using the ATLAS detector2011In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 83, no 5, p. 052003-Article in journal (Refereed)
    Abstract [en]

    Jet shapes have been measured in inclusive jet production in proton-proton collisions at root s = 7 TeV using 3 pb(-1) of data recorded by the ATLAS experiment at the LHC. Jets are reconstructed using the anti-k(t) algorithm with transverse momentum 30 GeV < p(T) < 600 GeV and rapidity in the region vertical bar y vertical bar < 2.8. The data are corrected for detector effects and compared to several leading-order QCD matrix elements plus parton shower Monte Carlo predictions, including different sets of parameters tuned to model fragmentation processes and underlying event contributions in the final state. The measured jets become narrower with increasing jet transverse momentum and the jet shapes present a moderate jet rapidity dependence. Within QCD, the data test a variety of perturbative and nonperturbative effects. In particular, the data show sensitivity to the details of the parton shower, fragmentation, and underlying event models in the Monte Carlo generators. For an appropriate choice of the parameters used in these models, the data are well described.

123 1 - 50 of 121
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf