R. Batley

University of Cambridge, Cambridge, England, United Kingdom

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Publications (93)

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    [Show abstract] [Hide abstract] ABSTRACT: A search is made for massive long-lived highly ionising particles with the ATLAS experiment at the Large Hadron Collider, using 3.1 pb-1 of pp collision data taken at sqrt(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 <= |q| <= 17e and masses 200 GeV <= m <= 1000 GeV are set in the range 1-12 pb for different hypotheses on the production mechanism.
    Full-text Article · Dec 2013 · Physics Letters B
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    [Show abstract] [Hide abstract] ABSTRACT: 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+ \ge n) / sigma(W+ \ge 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 \le 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.
    Full-text Article · Apr 2011 · Physics Letters B
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    [Show abstract] [Hide abstract] ABSTRACT: Muons from cosmic-ray interactions in the atmosphere provide a high-statistics source of particles that can be used to study the performance and calibration of the ATLAS detector. Cosmic-ray muons can penetrate to the cavern and deposit energy in all detector subsystems. Such events have played an important role in the commissioning of the detector since the start of the installation phase in 2005 and were particularly important for understanding the detector performance in the time prior to the arrival of the first LHC beams. Global cosmic-ray runs were undertaken in both 2008 and 2009 and these data have been used through to the early phases of collision data-taking as a tool for calibration, alignment and detector monitoring. These large datasets have also been used for detector performance studies, including investigations that rely on the combined performance of different subsystems. This paper presents the results of performance studies related to combined tracking, lepton identification and the reconstruction of jets and missing transverse energy. Results are compared to expectations based on a cosmic-ray event generator and a full simulation of the detector response.
    Full-text Article · Mar 2011 · European Physical Journal C
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    [Show abstract] [Hide abstract] ABSTRACT: 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 paper 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 in 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.
    Full-text Article · Mar 2011 · Physics Letters B
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    [Show abstract] [Hide abstract] ABSTRACT: 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 $\surd sNN$ = 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.
    Full-text Article · Mar 2011 · Physics Letters B
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    [Show abstract] [Hide abstract] ABSTRACT: Measurements are presented from proton-proton collisions at centre-of-mass energies of sqrt(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 models, including a new AMBT1 PYTHIA 6 tune. In all the kinematic regions considered, the particle multiplicities are higher than predicted by the Monte Carlo models. The central charged-particle multiplicity per event and unit of pseudorapidity, for tracks with pT >100 MeV, is measured to be 3.483 +- 0.009 (stat) +- 0.106 (syst) at sqrt(s) = 0.9 TeV and 5.630 +- 0.003 (stat) +- 0.169 (syst) at sqrt(s) = 7 TeV.
    Full-text Article · Jan 2011
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    [Show abstract] [Hide abstract] ABSTRACT: 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 the highest-$p_T$ 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, $p_T$ density, and average $p_T$ are measured. The data show a higher underlying event activity than that predicted by Monte Carlo models tuned to pre-LHC data.
    Full-text Article · Jan 2011
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    [Show abstract] [Hide abstract] ABSTRACT: A measurement of the production cross-section for top quark pairs($t\bar{t}$) in $pp$ collisions at $\sqrt{s}$=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-$t\bar{t}$ Standard Model processes are estimated using data-driven methods and determined to be $12.2 \pm 3.9$ events and $2.5 \pm 0.6$ events, respectively. The kinematic properties of the selected events are consistent with SM $t\bar{t}$ production. The inclusive top quark pair production cross-section is measured to be $\sigma_{t\bar{t}} = 145 \pm 31 ^{+42}_{-27}$ pb where the first uncertainty is statistical and the second systematic. The measurement agrees with perturbative QCD calculations.
    Full-text Article · Jan 2011
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    [Show abstract] [Hide abstract] ABSTRACT: 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 √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<728 GeV are excluded at 95% CL, providing the most sensitive limit on this model to date.
    Full-text Article · Jan 2011
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    [Show abstract] [Hide abstract] ABSTRACT: This paper presents the ATLAS collaboration’s first search for supersymmetry in final states containing jets, missing transverse momentum and one isolated electron or muon from √s = 7 TeV proton-proton collisions at the LHC. The data have been collected 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 earlier limits. For A0 = 0 GeV, tan β = 3, µ > 0 and assuming equal squark and gluino masses, gluino masses below 700 GeV are excluded with 95% confidence level.
    Full-text Article · Jan 2011
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    [Show abstract] [Hide abstract] ABSTRACT: 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 1.47 TeV.
    Full-text Article · Jan 2011
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    [Show abstract] [Hide abstract] ABSTRACT: Jet shapes have been measured in inclusive jet production in proton-proton collisions at sqrt(s) = 7 TeV using 3 pb^{-1} of data recorded by the ATLAS experiment at the LHC. Jets are reconstructed using the anti-kt algorithm with transverse momentum 30 GeV < pT < 600 GeV and rapidity in the region |y| < 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 non-perturbative 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.
    Full-text Article · Jan 2011
  • K. Bachas · T. Barber · R. Batley · [...] · Ch. Petridou
    [Show abstract] [Hide abstract] ABSTRACT: Studies of diboson production in pp collisions at center of mass energy of 14 TeV, predicted by the Standard Model electroweak interactions, will be performed with the ATLAS detector. Signals of the WW, ZW, ZZ, Wgamma, Zgamma channels are searched through their multi-lepton/photon final states while the sources of background are also studied. On this basis, lepton identification and selection efficiencies are optimized using events of Z decays to two leptons and the missing energy resolution and its systematic errors are studied via W boson decays to lepton and neutrino. Analysis with advanced techniques such as Boosted Decision Trees are applied for the WW, WZ and W/Z signals. Finally, the cross section measurements systematic and statistical uncertainties are estimated with respect to integrated luminosity of 0.1 to 10fb. The method of extracting anomalous triple-gauge coupling measurement is also presented.
    Article · Mar 2008 · Nuclear Physics B - Proceedings Supplements
  • V. Fanti · A. Lai · D. Marras · [...] · G. Linser
    Article · May 2007 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
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    V. Fanti · A. Lai · D. Marras · [...] · L. Widhalm
    [Show abstract] [Hide abstract] ABSTRACT: The beam and detector, used for the NA48 experiment, devoted to the measurement of Re(ε′/ε), and for the NA48/1 experiment on rare KS and neutral hyperon decays, are described.
    Full-text Article · May 2007 · Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment
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    [Show abstract] [Hide abstract] ABSTRACT: The inclusive production of charged hadrons in the collisions of quasi-real photons e+e- -> e+e- +X has been measured using the OPAL detector at LEP. The data were taken at e+e- centre-of-mass energies from 183 to 209 GeV. The differential cross-sections as a function of the transverse momentum and the pseudorapidity of the hadrons are compared to theoretical calculations of up to next-to-leading order (NLO) in the strong coupling constant alpha{s}. The data are also compared to a measurement by the L3 Collaboration, in which a large deviation from the NLO predictions is observed.
    Full-text Article · Jan 2007
  • [Show abstract] [Hide abstract] ABSTRACT: We have studied the distribution of charged particles recoiling from high pT (> 3.5 GeV/c) direct photons and neutral pions in pp collisions at √s = 63 GeV. One expects a different mixture of quark and gluon initiated jets in the two cases, with predominantly u-quark jets recoiling from direct photons. No significant differences are observed in our momentum range apart from the charge composition, with a larger positive to negative ratio for particles with pT > 1 GeV/c opposite direct photons than opposite π0.
    Article · Nov 2006 · Physica Scripta
  • A. Lai · D. Marras · R. Batley · [...] · E. Iacopini
    Article · Mar 2003
  • A Lai · D. Marras · R. Batley · [...] · L. Widhalm
    [Show abstract] [Hide abstract] ABSTRACT: A search for the decay KS → π0γγ has been made using the NA48 detector at the CERN SPS. Using data collected in 1999 during a 40-hour run with a high-intensity KS beam, an upper limit for the branching ratio BR(KS → π0γγ, z ≥ 0.2) < 3.3 x 10-7 has been obtained at 90% confidence level, where z = m2 γγ/mKO 2. © 2003 Published by Elsevier Science B.V.
    Article · Mar 2003
  • A. Lai · D. Marras · R. Batley · [...] · S. A. Wotton
    [Show abstract] [Hide abstract] ABSTRACT: A search for the decay KS-->pi0gammagamma has been made using the NA48 detector at the CERN SPS. Using data collected in 1999 during a 40-hour run with a high-intensity KS beam, an upper limit for the branching ratio BR(KS-->pi0gammagamma,z>=0.2)
    Article · Jan 2003

Publication Stats

925 Citations

Institutions

  • 1987-2013
    • University of Cambridge
      Cambridge, England, United Kingdom
  • 2007
    • Universität Siegen
      Siegen, North Rhine-Westphalia, Germany
  • 2001
    • University of Florence
      Florens, Tuscany, Italy
  • 1982-1986
    • CERN
      • Physics Department (PH)
      Genève, Geneva, Switzerland
  • 1983
    • Lund University
      • Department of Physics
      Lund, Skåne, Sweden
  • 1980
    • University of Oxford
      Oxford, England, United Kingdom