Showing papers by "Judith Katzy published in 2010"
TL;DR: 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, including supporting the detector description, interfacing the event generation, and combining the GEANT4 simulation of the response of the individual detectors.
Abstract: 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.
1,514 citations
TL;DR: In this article, the authors used the ATLAS detector to detect dijet asymmetry in the collisions of lead ions at the Large Hadron Collider and found that the transverse energies of dijets in opposite hemispheres become systematically more unbalanced with increasing event centrality, leading to a large number of events which contain highly asymmetric di jets.
Abstract: 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.
630 citations
TL;DR: An overview of the Tile Calorimeter performance as measured using random triggers, calibration data, data from cosmic ray muons and single beam data and the determination of the global energy scale was performed with an uncertainty of 4%.
Abstract: 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%.
203 citations
TL;DR: The ATLAS Inner Detector as mentioned in this paper is a composite tracking system consisting of silicon pixels, silicon strips and straw tubes in a 2 T magnetic field, which was completed in 2008 and the detector took part in data-taking with single LHC beams and cosmic rays.
Abstract: 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.
181 citations
TL;DR: The first measurements from proton-proton collisions recorded with the ATLAS detector at the LHC are presented in this paper, where the charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity, and the relationship between mean transversal momentum and charge multiplicity are measured for events with at least one charged particle in the kinematic range.
159 citations
TL;DR: Inclusive charm and beauty cross sections are measured in e-p and e+p neutral current collisions at HERA in the kinematic region of photon virtuality.
Abstract: Inclusive charm and beauty cross sections are measured in e-p and e+p neutral current collisions at HERA in the kinematic region of photon virtuality 5
139 citations
TL;DR: A search for new heavy particles manifested as resonances in two-jet final states in 7 TeV proton-proton collisions by the LHC is presented, extending the reach of previous experiments.
Abstract: 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.
137 citations
TL;DR: In this paper, the first measurements of the W and Z/gamma*-boson production cross sections in proton-proton collisions at 7 TeV are presented using data recorded by the ATLAS experiment at the LHC.
Abstract: First measurements of the W -> lnu and Z/gamma* -> ll (l = e, mu) production cross sections in proton-proton collisions at sqrt(s) = 7 TeV are presented using data recorded by the ATLAS experiment at the LHC. The results are based on 2250 W -> lnu and 179 Z/gamma* -> ll candidate events selected from a data set corresponding to an integrated luminosity of approximately 320 nb-1. The measured total W and Z/gamma*-boson production cross sections times the respective leptonic branching ratios for the combined electron and muon channels are $\stotW$ * BR(W -> lnu) = 9.96 +- 0.23(stat) +- 0.50(syst) +- 1.10(lumi) nb and $\stotZg$ * BR(Z/gamma* -> ll) = 0.82 +- 0.06(stat) +- 0.05(syst) +- 0.09(lumi) nb (within the invariant mass window 66 < m_ll < 116 GeV). The W/Z cross-section ratio is measured to be 11.7 +- 0.9(stat) +- 0.4(syst). In addition, measurements of the W+ and W- production cross sections and of the lepton charge asymmetry are reported. Theoretical predictions based on NNLO QCD calculations are found to agree with the measurements.
131 citations
TL;DR: In this article, an overview of the ATLAS liquid argon calorimeter performance measured in situ with random triggers, calibration data, cosmic muons, and LHC beam splash events is presented.
Abstract: 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.
123 citations
TL;DR: In this article, the authors measured the diffusion of rho and phi mesons at HERA with the H1 detector in the elastic and proton dissociative channels in the kinematic range of squared photon virtuality 2.5 < Q^2 < 60 GeV^2, photon-proton center of mass energy 35 < W < 180 GeV and squared four-momentum transfer to the proton |t| < 3 GeV|
Abstract: Diffractive electroproduction of rho and phi mesons is measured at HERA with the H1 detector in the elastic and proton dissociative channels. The data correspond to an integrated luminosity of 51 pb^-1. About 10500 rho and 2000 phi events are analysed in the kinematic range of squared photon virtuality 2.5 < Q^2 < 60 GeV^2, photon-proton centre of mass energy 35 < W < 180 GeV and squared four-momentum transfer to the proton |t| < 3 GeV^2. The total, longitudinal and transverse cross sections are measured as a function of Q^2, W and |t|. The measurements show a transition to a dominantly "hard" behaviour, typical of high gluon densities and small q\bar{q} dipoles, for Q^2 larger than 10 to 20 GeV^2. They support flavour independence of the diffractive exchange, expressed in terms of the scaling variable (Q^2 + M_V^2)/4, and proton vertex factorisation. The spin density matrix elements are measured as a function of kinematic variables. The ratio of the longitudinal to transverse cross sections, the ratio of the helicity amplitudes and their relative phases are extracted. Several of these measurements have not been performed before and bring new information on the dynamics of diffraction in a QCD framework. The measurements are discussed in the context of models using generalised parton distributions or universal dipole cross sections.
120 citations
TL;DR: In this paper, the production of jets in deepinelastic e+p scattering at low negative four momentum transfer squared (NSTS) was studied in the presence of a low negative 4 NSS.
Abstract: The production of jets is studied in deep-inelastic e+p scattering at low negative four momentum transfer squared 5
TL;DR: In this article, the production of leading neutrons, where the neutron carries a large fraction of the incoming proton's longitudinal momentum, is studied in deepinelastic positron-proton scattering at HERA.
Abstract: The production of leading neutrons, where the neutron carries a large fraction x_L of the incoming proton's longitudinal momentum, is studied in deep-inelastic positron-proton scattering at HERA. The data were taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of 122 pb^{-1}. The semi-inclusive cross section is measured in the phase space defined by the photon virtuality 6 < Q^2 < 100 GeV^2, Bjorken scaling variable 1.5x10^{-4} < x < 3x10^{-2}, longitudinal momentum fraction 0.32 < x_L < 0.95 and neutron transverse momentum p_T < 0.2 GeV. The leading neutron structure function, F_2^{LN(3)}(Q^2,x,x_L), and the fraction of deep-inelastic scattering events containing a leading neutron are studied as a function of Q^2, x and x_L. Assuming that the pion exchange mechanism dominates leading neutron production, the data provide constraints on the shape of the pion structure function.
TL;DR: In this paper, the performance of the ATLAS detector in the first half a million minimum bias events of the LHC collision data was investigated at center-of-mass energies of 0.9 TeV and 2.36 TeV.
Abstract: 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.
TL;DR: In this paper, the performance of the trigger and tracking chambers, their alignment, the detector control system, the data acquisition and the analysis programs are discussed. And 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 protonproton collisions.
Abstract: 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.
01 Oct 2010
TL;DR: In this article, a measurement of photo-and electroproduction of J/ψ mesons in ep scattering at HERA is presented, and the results are compared to theoretical predictions in the colour singlet model and in the framework of non-relativistic QCD.
Abstract: A measurement is presented of inelastic photo- and electroproduction of J/ψ mesons in ep scattering at HERA. The data were recorded with the H1 detector in the period from 2004 to 2007. Single and double differential cross sections are determined and the helicity distributions of the J/ψ mesons are analysed. The results are compared to theoretical predictions in the colour singlet model and in the framework of non-relativistic QCD. Calculations in the colour singlet model using a k
T
factorisation ansatz are able to give a good description of the data, while colour singlet model calculations to next-to-leading order in collinear factorisation underestimate the data.
TL;DR: In this paper, single and double-differential dijet cross sections in diffractive photoproduction based on a data sample with an integrated luminosity of 47 pb^-1.
Abstract: Measurements are presented of single and double-differential dijet cross sections in diffractive photoproduction based on a data sample with an integrated luminosity of 47 pb^-1. The events are of the type ep -> eXY, where the hadronic system X contains at least two jets and is separated by a large rapidity gap from the system Y, which consists of a leading proton or low-mass proton excitation. The dijet cross sections are compared with QCD calculations at next-to-leading order and with a Monte Carlo model based on leading order matrix elements with parton showers. The measured cross sections are smaller than those obtained from the next-to-leading order calculations by a factor of about 0.6. This suppression factor has no significant dependence on the fraction x_gamma of the photon four-momentum entering the hard subprocess. Ratios of the diffractive to the inclusive dijet cross sections are measured for the first time and are compared with Monte Carlo models.
TL;DR: In this article, the authors measured the production of D*(+/-)(2010) mesons in deepinelastic e( +/-)p scattering in the kinematic region of photon virtuality 100 1 5 GeV.
TL;DR: In this article, the ionization signals in the liquid argon of the ATLAS electromagnetic calorimeter are studied in detail using cosmic muons, and the drift time of the ionisation 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.
Abstract: 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.
TL;DR: In this article, the production of prompt photons is measured in the photoproduction regime of electron-proton scattering at HERA using a data sample corresponding to a total integrated luminosity of 340 pb(-1) collected by the H1 experiment.
Abstract: The production of prompt photons is measured in the photoproduction regime of electron-proton scattering at HERA. The analysis is based on a data sample corresponding to a total integrated luminosity of 340 pb(-1) collected by the H1 experiment. Cross sections are measured for photons with transverse momentum and pseudorapidity in the range 6< E-T(gamma) < 15 GeV and -1.0< eta(gamma) < 2.4, respectively. Cross sections for events with an additional jet are measured as a function of the transverse energy and pseudorapidity of the jet, and as a function of the fractional momenta x(gamma) and x(p) carried by the partons entering the hard scattering process. The correlation between the photon and the jet is also studied. The results are compared with QCD predictions based on the collinear and on the k(T) factorization approaches.
01 Apr 2010
TL;DR: This document describes how Monte Carlo (MC) generators can be used in the ATLAS software framework (Athena), written in C++ using Python scripts for job configuration.
Abstract: This document describes how Monte Carlo (MC) generators can be used in the ATLAS software framework (Athena). The framework is written in C++ using Python scripts for job configuration. Monte Carlo generators that provide the four-vectors describing the results of LHC collisions are written in general by third parties and are not part of Athena. These libraries are linked from the LCG Generator Services (GENSER) distribution. Generators are run from within Athena and the generated event output is put into a transient store, in HepMC format, using StoreGate. A common interface, implemented via inheritance of a GeneratorModule class, guarantees common functionality for the basic generation steps. The generator information can be accessed and manipulated by helper packages like TruthHelper. The ATLAS detector simulation as well access the truth information from StoreGate1. Steering is done through specific interfaces to allow for flexible configuration using ATLAS Python scripts. Interfaces to most general purpose generators, including: Pythia6, Pythia8, Herwig, Herwig++ and Sherpa are provided, as well as to more specialized packages, for example Phojet and Cascade. A second type of interface exist for the so called Matrix Element generators that only generate the particles produced in the hard scattering process and write events in the Les Houches event format. A generic interface to pass these events to Pythia6 and Herwig for parton showering and hadronisation has been written.
01 Jan 2010
01 Jan 2010
TL;DR: In this article, the authors measured the cross-sections of photons with transverse momentum and pseudorapidity in the range 6 < E T < 15GeV and −1.4, respectively.
Abstract: The production of prompt photons is measured in the photoproduction regime of electronproton scattering at HERA. The analysis is based on a data sample corresponding to a total integrated luminosity of 340 pb collected by the H1 experiment. Cross sections are measured for photons with transverse momentum and pseudorapidity in the range 6 < E T < 15GeV and −1.0 < η < 2.4, respectively. Cross sections for events with an additional jet are measured as a function of the transverse energy and pseudorapidity of the jet, and as a function of the fractional momenta xγ and xp carried by the partons entering the hard scattering process. The correlation between the photon and the jet is also studied. The results are compared with QCD predictions based on the collinear and on the kT factorisation approaches. Accepted by Eur. Phys. J. C F.D. Aaron, M. Aldaya Martin, C. Alexa, K. Alimujiang, V. Andreev, B. Antunovic, S. Backovic, A. Baghdasaryan, E. Barrelet, W. Bartel, K. Begzsuren, A. Belousov, J.C. Bizot, V. Boudry, I. Bozovic-Jelisavcic, J. Bracinik, G. Brandt, M. Brinkmann, V. Brisson, D. Bruncko, A. Bunyatyan, G. Buschhorn, L. Bystritskaya, A.J. Campbell, K.B. Cantun Avila, K. Cerny, V. Cerny, V. Chekelian, A. Cholewa, J.G. Contreras, J.A. Coughlan, G. Cozzika, J. Cvach, J.B. Dainton, K. Daum, M. Deak, Y. de Boer, B. Delcourt, M. Del Degan, J. Delvax, E.A. De Wolf, C. Diaconu, V. Dodonov, A. Dossanov, A. Dubak, G. Eckerlin, V. Efremenko, S. Egli, A. Eliseev, E. Elsen, A. Falkiewicz, L. Favart, A. Fedotov, R. Felst, J. Feltesse, J. Ferencei, D.-J. Fischer, M. Fleischer, A. Fomenko, E. Gabathuler, J. Gayler, S. Ghazaryan, A. Glazov, I. Glushkov, L. Goerlich, N. Gogitidze, M. Gouzevitch, C. Grab, T. Greenshaw, B.R. Grell, G. Grindhammer, S. Habib, D. Haidt, C. Helebrant, R.C.W. Henderson, E. Hennekemper, H. Henschel, M. Herbst, G. Herrera, M. Hildebrandt, K.H. Hiller, D. Hoffmann, R. Horisberger, T. Hreus, M. Jacquet, X. Janssen, L. Jonsson, A.W. Jung, H. Jung, M. Kapichine, J. Katzy, I.R. Kenyon, C. Kiesling, M. Klein, C. Kleinwort, T. Kluge, A. Knutsson, R. Kogler, P. Kostka, M. Kraemer, K. Krastev, J. Kretzschmar, A. Kropivnitskaya, K. Kruger, K. Kutak, M.P.J. Landon, W. Lange, G. Lastovicka-Medin, P. Laycock, A. Lebedev, G. Leibenguth, V. Lendermann, S. Levonian, G. Li, K. Lipka, A. Liptaj, B. List, J. List, N. Loktionova, R. Lopez-Fernandez, V. Lubimov, A. Makankine, E. Malinovski, P. Marage, Ll. Marti, H.-U. Martyn, S.J. Maxfield, A. Mehta, A.B. Meyer, H. Meyer, H. Meyer, J. Meyer, V. Michels, S. Mikocki, I. Milcewicz-Mika, F. Moreau, A. Morozov, J.V. Morris, M.U. Mozer, M. Mudrinic, K. Muller, P. Murin, Th. Naumann, P.R. Newman, C. Niebuhr, A. Nikiforov, D. Nikitin, G. Nowak, K. Nowak, M. Nozicka, B. Olivier, J.E. Olsson, S. Osman, D. Ozerov, V. Palichik, I. Panagoulias, M. Pandurovic, Th. Papadopoulou, C. Pascaud, G.D. Patel, O. Pejchal, E. Perez, A. Petrukhin, I. Picuric, S. Piec, D. Pitzl, R. Placakytė, B. Pokorny, R. Polifka, B. Povh, V. Radescu, A.J. Rahmat, N. Raicevic, A. Raspiareza, T. Ravdandorj, P. Reimer, E. Rizvi, P. Robmann, B. Roland, R. Roosen, A. Rostovtsev, M. Rotaru, J.E. Ruiz Tabasco, Z. Rurikova, S. Rusakov, D. Salek, D.P.C. Sankey, M. Sauter, E. Sauvan, S. Schmitt, L. Schoeffel, A. Schoning, H.-C. Schultz-Coulon, F. Sefkow, R.N. Shaw-West, L.N. Shtarkov, S. Shushkevich, T. Sloan, I. Smiljanic, Y. Soloviev, P. Sopicki, D. South, V. Spaskov, A. Specka, Z. Staykova, M. Steder, B. Stella, G. Stoicea, U. Straumann, D. Sunar, T. Sykora, V. Tchoulakov, G. Thompson, P.D. Thompson, T. Toll, F. Tomasz, T.H. Tran, D. Traynor, T.N. Trinh, P. Truol, I. Tsakov, B. Tseepeldorj, J. Turnau, K. Urban, A. Valkarova, C. Vallee, P. Van Mechelen, A. Vargas Trevino, Y. Vazdik, S. Vinokurova, V. Volchinski, M. von den Driesch, D. Wegener, Ch. Wissing, E. Wunsch, J. Žacek, J. Zalesak, Z. Zhang, A. Zhokin, T. Zimmermann, H. Zohrabyan, F. Zomer, and R. Zus 1 I. Physikalisches Institut der RWTH, Aachen, Germany 2 Vinca Institute of Nuclear Sciences, Belgrade, Serbia 3 School of Physics and Astronomy, University of Birmingham, Birmingham, UK