Showing papers by "Yorihito Sugaya 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: 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
Pusan National University1, Saga University2, Joint Institute for Nuclear Research3, National Taiwan University4, Arizona State University5, Graduate University for Advanced Studies6, Osaka University7, Yamagata University8, University of Chicago9, National Defense Academy of Japan10, Kyoto University11, University of Rochester12, CERN13
TL;DR: The first dedicated search for the rare neutral-kaon decay was carried out in the E391a experiment at the KEK 12-GeV proton synchrotron as mentioned in this paper.
Abstract: The first dedicated search for the rare neutral-kaon decay K{sub L}{sup 0{yields}{pi}0{nu}{nu}} has been carried out in the E391a experiment at the KEK 12-GeV proton synchrotron. The final upper limit of 2.6x10{sup -8} at the 90% confidence level was set on the branching ratio for the decay.
128 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 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.
78 citations
01 Oct 2010
Osaka University1, Pusan National University2, Konan University3, Japan Atomic Energy Agency4, Academia Sinica5, Nagoya University6, Kyoto University7, Seoul National University8, Ohio University9, Tohoku University10, Yamagata University11, Chiba University12, Wakayama Medical University13, University of Miyazaki14, National Defense Academy of Japan15, Tokyo Institute of Technology16, Chung Yuan Christian University17, Moscow State University18, University of Saskatchewan19, University of Minnesota20, Joint Institute for Nuclear Research21, Illinois Institute of Technology22, Michigan State University23
TL;DR: In this paper, a new bump structure was found at $W\ensuremath{\simeq}2.11\text{ }\text { }\mathrm{GeV}$ in the cross sections, which suggests that the bump might be produced by a nucleon resonance possibly with $J\enuremath{5}{2}$ or by a new reaction process, for example, an interference effect with the photoproduction having a similar bump structure.
Abstract: Differential cross sections and photon-beam asymmetries for the $\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}}p\ensuremath{\rightarrow}{K}^{+}\ensuremath{\Lambda}(1520)$ reaction have been measured with linearly polarized photon beams at energies from the threshold to 2.4 GeV at $0.6l\mathrm{cos} {\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}^{K}l1$. A new bump structure was found at $W\ensuremath{\simeq}2.11\text{ }\text{ }\mathrm{GeV}$ in the cross sections. The bump is not well reproduced by theoretical calculations introducing a nucleon resonance with $J\ensuremath{\le}\frac{3}{2}$. This result suggests that the bump might be produced by a nucleon resonance possibly with $J\ensuremath{\ge}\frac{5}{2}$ or by a new reaction process, for example, an interference effect with the $\ensuremath{\phi}$ photoproduction having a similar bump structure in the cross sections.
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.
Academia Sinica1, Osaka University2, Pusan National University3, Konan University4, Tohoku University5, Japan Atomic Energy Agency6, Nagoya University7, Ohio University8, Kyoto University9, Yamagata University10, Chiba University11, National Kaohsiung Normal University12, Wakayama Medical University13, University of Miyazaki14, National Defense Academy of Japan15, University of Saskatchewan16, University of Minnesota17, Tokyo Institute of Technology18, Michigan State University19
TL;DR: The LEPS/SPring-8 experiment made a comprehensive measurement of the spin-density matrix elements for ''ensuremath{\gamma}p''p, ''enuremath''d''p''d, ''ENuremath�n''pn''pn, and ''ensuresuremath`d''n''d\ensuredmath''n$ at forward production angles as discussed by the authors, where the natural parity Pomeron exchange processes remain dominant near threshold.
Abstract: The LEPS/SPring-8 experiment made a comprehensive measurement of the spin-density matrix elements for $\ensuremath{\gamma}p\ensuremath{\rightarrow}\ensuremath{\phi}p$, $\ensuremath{\gamma}d\ensuremath{\rightarrow}\ensuremath{\phi}pn$, and $\ensuremath{\gamma}d\ensuremath{\rightarrow}\ensuremath{\phi}d$ at forward production angles. A linearly polarized photon beam at ${E}_{\ensuremath{\gamma}}=1.6$--2.4 GeV was used for the production of $\ensuremath{\phi}$ mesons. The natural-parity Pomeron exchange processes remain dominant near threshold. The unnatural-parity processes of pseudoscalar exchange is visible in the production from the nucleons but is greatly reduced in the coherent production from deuterons. There is no strong ${E}_{\ensuremath{\gamma}}$ dependence, but there is some dependence on momentum transfer. A small but finite value of the spin-density matrix elements reflecting helicity-nonconserving amplitudes in the $t$-channel is observed.
Academia Sinica1, Kyoto University2, Osaka University3, Pusan National University4, Konan University5, Tohoku University6, Japan Atomic Energy Agency7, Nagoya University8, Ohio University9, Yamagata University10, Chiba University11, Wakayama Medical University12, University of Miyazaki13, National Defense Academy of Japan14, Tokyo Institute of Technology15, University of Saskatchewan16, University of Minnesota17, Michigan State University18
TL;DR: In this article, the deuteron photoproduction from linearly polarized photons at E γ = 1.5 − 2.4 GeV was measured and the nuclear transparency ratio was shown to show a large suppression, consistent with the A-dependence of the ratio observed in previous measurement with nuclear targets.
TL;DR: In this article, a muon track finding scheme based on monitored drift tube (MDT) signals is proposed to improve the performance of the muon Level-1 trigger of the ATLAS detector.
Abstract: The present muon Level-1 trigger of the ATLAS detector is given by dedicated detectors; RPC and TGC chambers in barrel and end-cap regions, respectively. The Monitored Drift Tube (MDT) chambers and the Cathode-Strip Chambers (CSC) are used for precision measurements of muon tracks. The performance of the muon Level-1 trigger is limited by the momentum resolution of the trigger chambers. In order to improve the trigger performance, a muon track finding scheme based on MDT signals is envisaged. Studies of the scheme and the algorithm are presented. The trigger latency is estimated to be approximately 3 μs.
14 May 2010
TL;DR: In this paper, the authors present a survey of the state-of-the-art methods to solve the problem of gender discrimination in the context of health care and mental health care.
Abstract: R. Abreu19, R. Achenbach35a, J. Adelman64, G. Aielli81a,81b, I.N. Aleksandrov38, E. Alexandrov38, J. Alison20, B.M.M. Allbrooke9, A. Aloisio62a,62b, F. Alonso42, B. Alvarez Gonzalez19, M.G. Alviggi62a,62b, N. Amram92, L.S. Ancu31, N. Andari64, C.F. Anders35b, G. Anders19, J.T. Anderson2, A. Andreani56a,56b, A. Andreazza56a,56b, V. Andrei35a, X.S. Anduaga42, I. Angelozzi63, N. Anjos4, A. Annovi75a,75b, M. Antonelli30, F. Anulli80a, M. Aoki39, I. Aracena86, S. Artz49, N. Asbah27, M. Atkinson100, J. Augusto77b, G. Avolio19, A.E. Baas35a, M. Backes19, E. Badescu16a, J.T. Baines79, S. Ballestrero87b, H.S. Bansil9, E.L. Barberio53, S.L. Barnes50, B.M. Barnett79, R. Bartoldus86, B. Bauss49, J.B. Beacham68, R. Beccherle75a,75b, H.P. Beck8,a, C.P. Bee89, M. Begel15, C. Belanger-Champagne52, W.H. Bell31, K. Bendtz88a,88b, Y. Benhammou92, M. Beretta30, D. Berge63, E. Bergeaas Kuutmann101, C. Bernard12, C. Bernius67, H. Bertelsen23, F. Bertolucci75a,75b, N.V. Biesuz75a,75b, M. Biglietti82a, K.M. Black12, R.E. Blair2, G. Blazey64, M. Bogdan20, A.G. Bogdanchikov65, C. Bohm88a, V. Boisvert45, T. Bold24a, A. Borga63, D. Boscherini11a, M. Bosman4, H. Boterenbrood63, A. Boveia19, J. Bracinik9, A. Brandt3, F. Brasolin11a, I.P. Brawn79, R. Brenner101, S. Bressler105, T.M. Bristow29, D. Britzger27, R. Brock54, W.K. Brooks21b, E. Brost69, A. Bruni11a, P. Bryant20, S.I. Buda16a, B. Burghgrave64, V. B ̈uscher49, J.M. Butler12, W. Buttinger15, G. Calderini48, R. Camacho Toro20, M. Campanelli46, A. Camplani56a,56b, M. Cano Bret22e, T. Cao26, M. Caprini16a, R. Caputo49, R. Cardarelli81a, D. Casadei46, M.P. Casado4, V. Cavaliere100, V. Cavasinni75a,75b, A. Cerri90, L. Cerrito44, D. Chakraborty64, P. Chang100, C.A. Chavez Barajas90, S. Cheatham91, A. Chegwidden54, H. Chen15, K. Chen15, Y. Chen40, Y. Cheng20, J.T. Childers2, G. Chiodini43a, R.T. Chislett46, A. Chitan16a, V. Christodoulou46, G. Ciapetti80a,80b, S. Citraro75a,75b, M. Citterio56a, T. Colombo35c, P. Conde Mui ̃no77a,77b, I.A. Connelly45, A.C. Contescu16c, F. Conventi62a,b, B.D. Cooper46, M. Corradi11a, F. Corriveau52,c, A. Corso-Radu99, R. Coura Torres14a, K. Cranmer67, F. Crescioli48, G.J. Crone46, J. Cummings108, M. D’ascanio19, M.J. Da Cunha Sargedas De Sousa77a,77b, M. Dam23, A.C. Daniells9, L. Danielsen19, O. Davignon48, P. Davison46, S. De Cecco48, D. De Pedis80a, A. De Santo90, J. Degenhardt73, I. Deigaard63, L. Dell’Asta12, M. Dell’Orso75a,75b, M. Della Pietra62a,b, S. Demers108, P.O. Deviveiros19, S. Dhaliwal13, A. Di Ciaccio81a,81b, A. Di Mattia91, M.A. Diaz21a, J.I. Djuvsland35a, S. Donati75a,75b, M.T. Dova42, G. Drake2, S. Dubrov65, M. Dunford35a, D. Edmunds54, E. Eisenhandler44, N. Ellis19, D. Emeliyanov79, I. Ermoline54, E. Etzion92, H. Evans37, S. Falciano80a, S. Farrell6, S.M. Farrington103, P. Farthouat19, P.J.W. Faulkner9, D. Fazio19, W. Fedorko102, R. Ferrari72a, A. Ferretto Parodi32a,32b, W.C. Fisher54, D. Francis19, M. Frate99, S. Fratina73, S.T. French18, S.M. Fressard-Batraneanu19, D.M. Front105, C. Fukunaga95, T. Fusayasu60, S. Gadomski31, G. Galster23, N. Garelli86, M. Gatta30, C.N.P. Gee79, C. Gentsos93, S. George45, D. Gerbaudo99, M. Ghibaudi19, S. Giagu80a,80b, P. Giannetti75a,75b, R. Giordano62a,62b, F.M. Giorgi7, M. Giulini35b, S. Gkaitatzis93, J. Glatzer19, R. Gon ̧calo77a, M.L. Gonzalez Silva17, B. Gorini19, E. Gorini43a,43b, I. Grabowska-Bold24a, J. Gramling31, B. Green45, Z.D. Greenwood47,d, K. Gregersen46, G.C. Grossi47, Z.J. Grout90, A. Haas67, S. Haas19, D.R. Hadley9, P. Hanke35a, P.F. Harrison103, M. Hasegawa40, S. Hasegawa61, Y. Hasegawa84, R. Hauser54, S.J. Head9, S. Heim73, L. Helary12, S. Hellman88a,88b, A.M. Henriques Correia19, R. Herrberg-Schubert7, J.W. Hetherly26, K. Higuchi96, S.J. Hillier9, S. Hirayama94, N. Hod63, D. Hoffmann51, T.M. Hong76,