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Measurements of Wγ and Zγ production in pp collisions at s=7 TeV with the ATLAS detector at the LHC

Physical Review D 2013年第11期87卷 112003-112003页

作者： G. Aad T. Abajyan B. Abbott J. Abdallah S. Abdel Khalek A. A. Abdelalim O. Abdinov R. Aben B. Abi M. Abolins O. S. AbouZeid H. Abramowicz H. Abreu B. S. Acharya L. Adamczyk D. L. Adams T. N. Addy J. Adelman S. Adomeit P. Adragna T. Adye S. Aefsky J. A. Aguilar-Saavedra M. Agustoni S. P. Ahlen F. Ahles A. Ahmad M. Ahsan G. Aielli T. P. A. Åkesson G. Akimoto A. V. Akimov M. A. Alam J. Albert S. Albrand M. Aleksa I. N. Aleksandrov F. Alessandria C. Alexa G. Alexander G. Alexandre T. Alexopoulos M. Alhroob M. Aliev G. Alimonti J. Alison B. M. M. Allbrooke L. J. Allison P. P. Allport S. E. Allwood-Spiers J. Almond A. Aloisio R. Alon A. Alonso F. Alonso A. Altheimer B. Alvarez Gonzalez M. G. Alviggi K. Amako C. Amelung V. V. Ammosov S. P. Amor Dos Santos A. Amorim S. Amoroso N. Amram C. Anastopoulos L. S. Ancu N. Andari T. Andeen C. F. Anders G. Anders K. J. Anderson A. Andreazza V. Andrei M-L. Andrieux X. S. Anduaga S. Angelidakis P. Anger A. Angerami F. Anghinolfi A. Anisenkov N. Anjos A. Annovi A. Antonaki M. Antonelli A. Antonov J. Antos F. Anulli M. Aoki S. Aoun L. Aperio Bella R. Apolle G. Arabidze I. Aracena Y. Arai A. T. H. Arce S. Arfaoui J-F. Arguin S. Argyropoulos E. Arik M. Arik A. J. Armbruster O. Arnaez V. Arnal A. Artamonov G. Artoni D. Arutinov S. Asai S. Ask B. Åsman D. Asner L. Asquith K. Assamagan A. Astbury M. Atkinson B. Aubert B. Auerbach E. Auge K. Augsten M. Aurousseau G. Avolio D. Axen G. Azuelos Y. Azuma M. A. Baak G. Baccaglioni C. Bacci A. M. Bach H. Bachacou K. Bachas M. Backes M. Backhaus J. Backus Mayes E. Badescu P. Bagnaia Y. Bai D. C. Bailey T. Bain J. T. Baines O. K. Baker S. Baker P. Balek F. Balli E. Banas P. Banerjee Sw. Banerjee D. Banfi A. Bangert V. Bansal H. S. Bansil L. Barak S. P. Baranov T. Barber E. L. Barberio D. Barberis M. Barbero D. Y. Bardin T. Barillari M. Barisonzi T. Barklow N. Barlow B. M. Barnett R. M. Barnett A. Baroncelli G. Barone A. J. Barr F. Barreiro J. Barreiro Guimarães da Costa R. Bartoldus A. E. Barton V. Bartsch A. Basye R. L. Bates L. Batkova J. R. Bat Fakultät für Mathematik und Physik Albert-Ludwigs-Universität Freiburg Germany Physikalisches Institut University of Bonn Bonn Germany Homer L. Dodge Department of Physics and Astronomy University of Oklahoma Norman Oklahoma USA Institut de Física d’Altes Energies and Departament de Física de la Universitat Autònoma de Barcelona and ICREA Barcelona Spain LAL Université Paris-Sud and CNRS/IN2P3 Orsay France Section de Physique Université de Genève Geneva Switzerland Institute of Physics Azerbaijan Academy of Sciences Baku Azerbaijan Nikhef National Institute for Subatomic Physics and University of Amsterdam Amsterdam Netherlands Department of Physics Oklahoma State University Stillwater Oklahoma USA Department of Physics and Astronomy Michigan State University East Lansing Michigan USA Department of Physics University of Toronto Toronto Ontario Canada Raymond and Beverly Sackler School of Physics and Astronomy Tel Aviv University Tel Aviv Israel DSM/IRFU (Institut de Recherches sur les Lois Fondamentales de l’Univers) CEA Saclay (Commissariat à l’Energie Atomique et aux Energies Alternatives) Gif-sur-Yvette France INFN Gruppo Collegato di Udine Italy ICTP Trieste Italy AGH University of Science and Technology Faculty of Physics and Applied Computer Science Krakow Poland Physics Department Brookhaven National Laboratory Upton New York USA Department of Physics Hampton University Hampton Virginia USA Department of Physics Yale University New Haven Connecticut USA Fakultät für Physik Ludwig-Maximilians-Universität München München Germany School of Physics and Astronomy Queen Mary University of London London United Kingdom Particle Physics Department Rutherford Appleton Laboratory Didcot United Kingdom Department of Physics Brandeis University Waltham Massachusetts USA Departamento de Fisica Teorica y del Cosmos and CAFPE Universidad de Granada Granada Spain Albert Einstein Center for Fundamental Physics and Laboratory for High Energy Physics U

The integrated and differential fiducial cross sections for the production of a W or Z boson in association with a high-energy photon are measured using pp collisions at s=7 TeV. The analyses use a data sample with an integrated luminosity of 4.6 fb−1 collected by the ATLAS detector during the 2011 LHC data-taking period. Events are selected using leptonic decays of the W and Z bosons [W(eν,μν) and Z(e+e−,μ+μ−,νν¯)] with the requirement of an associated isolated photon. The data are used to test the electroweak sector of the Standard Model and search for evidence for new phenomena. The measurements are used to probe the anomalous WWγ, ZZγ, and Zγγ triple-gauge-boson couplings and to search for the production of vector resonances decaying to Zγ and Wγ. No deviations from Standard Model predictions are observed and limits are placed on anomalous triple-gauge-boson couplings and on the production of new vector meson resonances.

关键词： LARGE Hadron Collider (France & Switzerland) COLLISIONS (Nuclear physics) NUCLEAR counters CROSS sections (Nuclear physics) NUCLEAR energy STANDARD model (Nuclear physics)

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Search for tt¯ resonances in the lepton plus jets final state with ATLAS using 4.7 fb−1 of pp collisions at s=7 TeV

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Physical Review D 2013年第1期88卷 012004-012004页

作者： G. Aad T. Abajyan B. Abbott J. Abdallah S. Abdel Khalek A. A. Abdelalim O. Abdinov R. Aben B. Abi M. Abolins O. S. AbouZeid H. Abramowicz H. Abreu Y. Abulaiti B. S. Acharya L. Adamczyk D. L. Adams T. N. Addy J. Adelman S. Adomeit P. Adragna T. Adye S. Aefsky J. A. Aguilar-Saavedra M. Agustoni S. P. Ahlen F. Ahles A. Ahmad M. Ahsan G. Aielli T. P. A. Åkesson G. Akimoto A. V. Akimov M. A. Alam J. Albert S. Albrand M. Aleksa I. N. Aleksandrov F. Alessandria C. Alexa G. Alexander G. Alexandre T. Alexopoulos M. Alhroob M. Aliev G. Alimonti J. Alison B. M. M. Allbrooke L. J. Allison P. P. Allport S. E. Allwood-Spiers J. Almond A. Aloisio R. Alon A. Alonso F. Alonso A. Altheimer B. Alvarez Gonzalez M. G. Alviggi K. Amako C. Amelung V. V. Ammosov S. P. Amor Dos Santos A. Amorim S. Amoroso N. Amram C. Anastopoulos L. S. Ancu N. Andari T. Andeen C. F. Anders G. Anders K. J. Anderson A. Andreazza V. Andrei X. S. Anduaga S. Angelidakis P. Anger A. Angerami F. Anghinolfi A. Anisenkov N. Anjos A. Annovi A. Antonaki M. Antonelli A. Antonov J. Antos F. Anulli M. Aoki L. Aperio Bella R. Apolle G. Arabidze I. Aracena Y. Arai A. T. H. Arce S. Arfaoui J-F. Arguin S. Argyropoulos E. Arik M. Arik A. J. Armbruster O. Arnaez V. Arnal A. Artamonov G. Artoni D. Arutinov S. Asai S. Ask B. Åsman L. Asquith K. Assamagan R. Astalos A. Astbury M. Atkinson B. Auerbach E. Auge K. Augsten M. Aurousseau G. Avolio D. Axen G. Azuelos Y. Azuma M. A. Baak G. Baccaglioni C. Bacci A. M. Bach H. Bachacou K. Bachas M. Backes M. Backhaus J. Backus Mayes E. Badescu P. Bagnaia Y. Bai D. C. Bailey T. Bain J. T. Baines O. K. Baker S. Baker P. Balek F. Balli E. Banas P. Banerjee Sw. Banerjee D. Banfi A. Bangert V. Bansal H. S. Bansil L. Barak S. P. Baranov T. Barber E. L. Barberio D. Barberis M. Barbero D. Y. Bardin T. Barillari M. Barisonzi T. Barklow N. Barlow B. M. Barnett R. M. Barnett A. Baroncelli G. Barone A. J. Barr F. Barreiro J. Barreiro Guimarães da Costa R. Bartoldus A. E. Barton V. Bartsch A. Basye R. L. Bates L. Batkova J. R. Batley A. Battaglia M Fakultät für Mathematik und Physik Albert-Ludwigs-Universität Freiburg Germany Physikalisches Institut University of Bonn Bonn Germany Homer L. Dodge Department of Physics and Astronomy University of Oklahoma Norman Oklahoma USA Institut de Física d’Altes Energies and Departament de Física de la Universitat Autònoma de Barcelona and ICREA Barcelona Spain LAL Université Paris-Sud and CNRS/IN2P3 Orsay France Section de Physique Université de Genève Geneva Switzerland Institute of Physics Azerbaijan Academy of Sciences Baku Azerbaijan Nikhef National Institute for Subatomic Physics and University of Amsterdam Amsterdam Netherlands Department of Physics Oklahoma State University Stillwater Oklahoma USA Department of Physics and Astronomy Michigan State University East Lansing Michigan USA Department of Physics University of Toronto Toronto Ontario Canada Raymond and Beverly Sackler School of Physics and Astronomy Tel Aviv University Tel Aviv Israel DSM/IRFU (Institut de Recherches sur les Lois Fondamentales de l’Univers) CEA Saclay (Commissariat à l’Energie Atomique et aux Energies Alternatives) Gif-sur-Yvette France Department of Physics Stockholm University Sweden The Oskar Klein Centre Stockholm Sweden INFN Gruppo Collegato di Udine Italy ICTP Trieste Italy AGH University of Science and Technology Faculty of Physics and Applied Computer Science Krakow Poland Physics Department Brookhaven National Laboratory Upton New York USA Department of Physics Hampton University Hampton Virginia USA Department of Physics Yale University New Haven Connecticut USA Fakultät für Physik Ludwig-Maximilians-Universität München München Germany School of Physics and Astronomy Queen Mary University of London London United Kingdom Particle Physics Department Rutherford Appleton Laboratory Didcot United Kingdom Department of Physics Brandeis University Waltham Massachusetts USA Departamento de Fisica Teorica y del Cosmos and CAFPE Universidad de Granada Granada

A search for new particles that decay into top quark pairs (tt¯) is performed with the ATLAS experiment at the LHC using an integrated luminosity of 4.7 fb−1 of proton–proton (pp) collision data collected at a center-of-mass energy s=7 TeV. In the tt¯→WbWb decay, the lepton plus jets final state is used, where one W boson decays leptonically and the other hadronically. The tt¯ system is reconstructed using both small-radius and large-radius jets, the latter being supplemented by a jet substructure analysis. A search for local excesses in the number of data events compared to the Standard Model expectation in the tt¯ invariant mass spectrum is performed. No evidence for a tt¯ resonance is found and 95% credibility-level limits on the production rate are determined for massive states predicted in two benchmark models. The upper limits on the cross section times branching ratio of a narrow Z′ resonance range from 5.1 pb for a boson mass of 0.5 TeV to 0.03 pb for a mass of 3 TeV. A narrow leptophobic topcolor Z′ resonance with a mass below 1.74 TeV is excluded. Limits are also derived for a broad color-octet resonance with Γ/m=15.3%. A Kaluza–Klein excitation of the gluon in a Randall–Sundrum model is excluded for masses below 2.07 TeV.

关键词： LEPTONS (Nuclear physics) PROTON-proton interactions MASS spectrometry STANDARD model (Nuclear physics) RESONANCE KALUZA-Klein excitations

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Search for new phenomena in events with three charged leptons at s=7 TeV with the ATLAS detector

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Physical Review D 2013年第5期87卷 052002-052002页

作者： G. Aad T. Abajyan B. Abbott J. Abdallah S. Abdel Khalek A. A. Abdelalim O. Abdinov R. Aben B. Abi M. Abolins O. S. AbouZeid H. Abramowicz H. Abreu B. S. Acharya L. Adamczyk D. L. Adams T. N. Addy J. Adelman S. Adomeit P. Adragna T. Adye S. Aefsky J. A. Aguilar-Saavedra M. Agustoni M. Aharrouche S. P. Ahlen F. Ahles A. Ahmad M. Ahsan G. Aielli T. P. A. Åkesson G. Akimoto A. V. Akimov M. S. Alam M. A. Alam J. Albert S. Albrand M. Aleksa I. N. Aleksandrov F. Alessandria C. Alexa G. Alexander G. Alexandre T. Alexopoulos M. Alhroob M. Aliev G. Alimonti J. Alison B. M. M. Allbrooke P. P. Allport S. E. Allwood-Spiers J. Almond A. Aloisio R. Alon A. Alonso F. Alonso A. Altheimer B. Alvarez Gonzalez M. G. Alviggi K. Amako C. Amelung V. V. Ammosov S. P. Amor Dos Santos A. Amorim N. Amram C. Anastopoulos L. S. Ancu N. Andari T. Andeen C. F. Anders G. Anders K. J. Anderson A. Andreazza V. Andrei M.-L. Andrieux X. S. Anduaga S. Angelidakis P. Anger A. Angerami F. Anghinolfi A. Anisenkov N. Anjos A. Annovi A. Antonaki M. Antonelli A. Antonov J. Antos F. Anulli M. Aoki S. Aoun L. Aperio Bella R. Apolle G. Arabidze I. Aracena Y. Arai A. T. H. Arce S. Arfaoui J.-F. Arguin S. Argyropoulos E. Arik M. Arik A. J. Armbruster O. Arnaez V. Arnal A. Artamonov G. Artoni D. Arutinov S. Asai S. Ask B. Åsman L. Asquith K. Assamagan A. Astbury M. Atkinson B. Aubert E. Auge K. Augsten M. Aurousseau G. Avolio D. Axen G. Azuelos Y. Azuma M. A. Baak G. Baccaglioni C. Bacci A. M. Bach H. Bachacou K. Bachas M. Backes M. Backhaus J. Backus Mayes E. Badescu P. Bagnaia S. Bahinipati Y. Bai D. C. Bailey T. Bain J. T. Baines O. K. Baker M. D. Baker S. Baker P. Balek E. Banas P. Banerjee Sw. Banerjee D. Banfi A. Bangert V. Bansal H. S. Bansil L. Barak S. P. Baranov A. Barbaro Galtieri T. Barber E. L. Barberio D. Barberis M. Barbero D. Y. Bardin T. Barillari M. Barisonzi T. Barklow N. Barlow B. M. Barnett R. M. Barnett A. Baroncelli G. Barone A. J. Barr F. Barreiro J. Barreiro Guimarães da Costa R. Bartoldus A. E. Barton V. Bartsch A. Basye R. L. Bates L. Fakultät für Mathematik und Physik Albert-Ludwigs-Universität Freiburg Germany Physikalisches Institut University of Bonn Bonn Germany Homer L. Dodge Department of Physics and Astronomy University of Oklahoma Norman Oklahoma USA Institut de Física d’Altes Energies and Departament de Física de la Universitat Autònoma de Barcelona and ICREA Barcelona Spain LAL Université Paris-Sud and CNRS/IN2P3 Orsay France Section de Physique Université de Genève Geneva Switzerland Institute of Physics Azerbaijan Academy of Sciences Baku Azerbaijan Nikhef National Institute for Subatomic Physics and University of Amsterdam Amsterdam Netherlands Department of Physics Oklahoma State University Stillwater Oklahoma USA Department of Physics and Astronomy Michigan State University East Lansing Michigan USA Department of Physics University of Toronto Toronto Ontario Canada Raymond and Beverly Sackler School of Physics and Astronomy Tel Aviv University Tel Aviv Israel DSM/IRFU (Institut de Recherches sur les Lois Fondamentales de l’Univers) CEA Saclay (Commissariat à l’Energie Atomique et aux Energies Alternatives) Gif-sur-Yvette France INFN Gruppo Collegato di Udine Udine Italy ICTP Trieste Italy AGH University of Science and Technology Faculty of Physics and Applied Computer Science Krakow Poland Physics Department Brookhaven National Laboratory Upton New York USA Department of Physics Hampton University Hampton Virginia USA Department of Physics Yale University New Haven Connecticut USA Fakultät für Physik Ludwig-Maximilians-Universität München München Germany School of Physics and Astronomy Queen Mary University of London London United Kingdom Particle Physics Department Rutherford Appleton Laboratory Didcot United Kingdom Department of Physics Brandeis University Waltham Massachusetts USA Departamento de Fisica Teorica y del Cosmos and CAFPE Universidad de Granada Granada Spain Albert Einstein Center for Fundamental Physics and Laboratory for High Energy Ph

A generic search for anomalous production of events with at least three charged leptons is presented. The search uses a pp-collision data sample at a center-of-mass energy of s=7 TeV corresponding to 4.6 fb−1 of integrated luminosity collected in 2011 by the ATLAS detector at the CERN Large Hadron Collider. Events are required to contain at least two electrons or muons, while the third lepton may either be an additional electron or muon, or a hadronically decaying tau lepton. Events are categorized by the presence or absence of a reconstructed tau-lepton or Z-boson candidate decaying to leptons. No significant excess above backgrounds expected from Standard Model processes is observed. Results are presented as upper limits on event yields from non-Standard-Model processes producing at least three prompt, isolated leptons, given as functions of lower bounds on several kinematic variables. Fiducial efficiencies for model testing are also provided. The use of the results is illustrated by setting upper limits on the production of doubly charged Higgs bosons decaying to same-sign lepton pairs.

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Measurement of upsilon production in 7 TeV pp collisions at ATLAS

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Physical Review D 2013年第5期87卷 052004-052004页

作者： G. Aad T. Abajyan B. Abbott J. Abdallah S. Abdel Khalek A. A. Abdelalim O. Abdinov R. Aben B. Abi M. Abolins O. S. AbouZeid H. Abramowicz H. Abreu B. S. Acharya L. Adamczyk D. L. Adams T. N. Addy J. Adelman S. Adomeit P. Adragna T. Adye S. Aefsky J. A. Aguilar-Saavedra M. Agustoni M. Aharrouche S. P. Ahlen F. Ahles A. Ahmad M. Ahsan G. Aielli T. P. A. Åkesson G. Akimoto A. V. Akimov M. S. Alam M. A. Alam J. Albert S. Albrand M. Aleksa I. N. Aleksandrov F. Alessandria C. Alexa G. Alexander G. Alexandre T. Alexopoulos M. Alhroob M. Aliev G. Alimonti J. Alison B. M. M. Allbrooke P. P. Allport S. E. Allwood-Spiers J. Almond A. Aloisio R. Alon A. Alonso F. Alonso A. Altheimer B. Alvarez Gonzalez M. G. Alviggi K. Amako C. Amelung V. V. Ammosov S. P. Amor Dos Santos A. Amorim N. Amram C. Anastopoulos L. S. Ancu N. Andari T. Andeen C. F. Anders G. Anders K. J. Anderson A. Andreazza V. Andrei M-L. Andrieux X. S. Anduaga S. Angelidakis P. Anger A. Angerami F. Anghinolfi A. Anisenkov N. Anjos A. Annovi A. Antonaki M. Antonelli A. Antonov J. Antos F. Anulli M. Aoki S. Aoun L. Aperio Bella R. Apolle G. Arabidze I. Aracena Y. Arai A. T. H. Arce S. Arfaoui J-F. Arguin S. Argyropoulos E. Arik M. Arik A. J. Armbruster O. Arnaez V. Arnal A. Artamonov G. Artoni D. Arutinov S. Asai S. Ask B. Åsman L. Asquith K. Assamagan A. Astbury M. Atkinson B. Aubert E. Auge K. Augsten M. Aurousseau G. Avolio D. Axen G. Azuelos Y. Azuma M. A. Baak G. Baccaglioni C. Bacci A. M. Bach H. Bachacou K. Bachas M. Backes M. Backhaus J. Backus Mayes E. Badescu P. Bagnaia S. Bahinipati Y. Bai D. C. Bailey T. Bain J. T. Baines O. K. Baker M. D. Baker S. Baker P. Balek E. Banas P. Banerjee Sw. Banerjee D. Banfi A. Bangert V. Bansal H. S. Bansil L. Barak S. P. Baranov A. Barbaro Galtieri T. Barber E. L. Barberio D. Barberis M. Barbero D. Y. Bardin T. Barillari M. Barisonzi T. Barklow N. Barlow B. M. Barnett R. M. Barnett A. Baroncelli G. Barone A. J. Barr F. Barreiro J. Barreiro Guimarães da Costa R. Bartoldus A. E. Barton V. Bartsch A. Basye R. L. Bates L. B Fakultät für Mathematik und Physik Albert-Ludwigs-Universität Freiburg Germany Physikalisches Institut University of Bonn Bonn Germany Homer L. Dodge Department of Physics and Astronomy University of Oklahoma Norman Oklahoma USA Institut de Física d’Altes Energies and Departament de Física de la Universitat Autònoma de Barcelona and ICREA Barcelona Spain LAL Université Paris-Sud and CNRS/IN2P3 Orsay France Section de Physique Université de Genève Geneva Switzerland Institute of Physics Azerbaijan Academy of Sciences Baku Azerbaijan Nikhef National Institute for Subatomic Physics and University of Amsterdam Amsterdam Netherlands Department of Physics Oklahoma State University Stillwater Oklahoma USA Department of Physics and Astronomy Michigan State University East Lansing Michigan USA Department of Physics University of Toronto Toronto Ontario Canada Raymond and Beverly Sackler School of Physics and Astronomy Tel Aviv University Tel Aviv Israel DSM/IRFU (Institut de Recherches sur les Lois Fondamentales de l’Univers) CEA Saclay (Commissariat a l’Energie Atomique) Gif-sur-Yvette France INFN Gruppo Collegato di Udine Italy ICTP Trieste Italy AGH University of Science and Technology Faculty of Physics and Applied Computer Science Krakow Poland Physics Department Brookhaven National Laboratory Upton New York USA Department of Physics Hampton University Hampton Virginia USA Department of Physics Yale University New Haven Connecticut USA Fakultät für Physik Ludwig-Maximilians-Universität München München Germany School of Physics and Astronomy Queen Mary University of London London United Kingdom Particle Physics Department Rutherford Appleton Laboratory Didcot United Kingdom Department of Physics Brandeis University Waltham Massachusetts USA Departamento de Fisica Teorica y del Cosmos and CAFPE Universidad de Granada Granada Spain Albert Einstein Center for Fundamental Physics and Laboratory for High Energy Physics University of Bern Bern Swi

Using 1.8 fb−1 of pp collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the Large Hadron Collider, we present measurements of the production cross sections of Υ(1S,2S,3S) mesons. Υ mesons are reconstructed using the dimuon decay mode. Total production cross sections for pT<70 GeV and in the rapidity interval |yΥ|<2.25 are measured to be, 8.01±0.02±0.36±0.31 nb, 2.05±0.01±0.12±0.08 nb, and 0.92±0.01±0.07±0.04 nb, respectively, with uncertainties separated into statistical, systematic, and luminosity measurement effects. In addition, differential cross section times dimuon branching fractions for Υ(1S), Υ(2S), and Υ(3S) as a function of Υ transverse momentum pT and rapidity are presented. These cross sections are obtained assuming unpolarized production. If the production polarization is fully transverse or longitudinal with no azimuthal dependence in the helicity frame, the cross section may vary by approximately ±20%. If a nontrivial azimuthal dependence is considered, integrated cross sections may be significantly enhanced by a factor of 2 or more. We compare our results to several theoretical models of Υ meson production, finding that none provide an accurate description of our data over the full range of Υ transverse momenta accessible with this data set.

关键词： UPSILON meson CROSS sections (Nuclear physics) POLARIZATION (Nuclear physics) LARGE Hadron Collider (France & Switzerland) center of mass COLLISIONS (Nuclear physics) NUCLEAR counters

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Measurement of W+W− production in pp collisions at s=7 TeV with the ATLAS detector and limits on anomalous WWZ and WWγ couplings

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Physical Review D 2013年第11期87卷 112001-112001页

作者： G. Aad T. Abajyan B. Abbott J. Abdallah S. Abdel Khalek A. A. Abdelalim O. Abdinov R. Aben B. Abi M. Abolins O. S. AbouZeid H. Abramowicz H. Abreu B. S. Acharya L. Adamczyk D. L. Adams T. N. Addy J. Adelman S. Adomeit P. Adragna T. Adye S. Aefsky J. A. Aguilar-Saavedra M. Agustoni M. Aharrouche S. P. Ahlen F. Ahles A. Ahmad M. Ahsan G. Aielli T. Akdogan T. P. A. Åkesson G. Akimoto A. V. Akimov M. S. Alam M. A. Alam J. Albert S. Albrand M. Aleksa I. N. Aleksandrov F. Alessandria C. Alexa G. Alexander G. Alexandre T. Alexopoulos M. Alhroob M. Aliev G. Alimonti J. Alison B. M. M. Allbrooke P. P. Allport S. E. Allwood-Spiers J. Almond A. Aloisio R. Alon A. Alonso F. Alonso A. Altheimer B. Alvarez Gonzalez M. G. Alviggi K. Amako C. Amelung V. V. Ammosov S. P. Amor Dos Santos A. Amorim N. Amram C. Anastopoulos L. S. Ancu N. Andari T. Andeen C. F. Anders G. Anders K. J. Anderson A. Andreazza V. Andrei M-L. Andrieux X. S. Anduaga S. Angelidakis P. Anger A. Angerami F. Anghinolfi A. Anisenkov N. Anjos A. Annovi A. Antonaki M. Antonelli A. Antonov J. Antos F. Anulli M. Aoki S. Aoun L. Aperio Bella R. Apolle G. Arabidze I. Aracena Y. Arai A. T. H. Arce S. Arfaoui J-F. Arguin E. Arik M. Arik A. J. Armbruster O. Arnaez V. Arnal C. Arnault A. Artamonov G. Artoni D. Arutinov S. Asai S. Ask B. Åsman L. Asquith K. Assamagan A. Astbury M. Atkinson B. Aubert E. Auge K. Augsten M. Aurousseau G. Avolio R. Avramidou D. Axen G. Azuelos Y. Azuma M. A. Baak G. Baccaglioni C. Bacci A. M. Bach H. Bachacou K. Bachas M. Backes M. Backhaus J. Backus Mayes E. Badescu P. Bagnaia S. Bahinipati Y. Bai D. C. Bailey T. Bain J. T. Baines O. K. Baker M. D. Baker S. Baker P. Balek E. Banas P. Banerjee Sw. Banerjee D. Banfi A. Bangert V. Bansal H. S. Bansil L. Barak S. P. Baranov A. Barbaro Galtieri T. Barber E. L. Barberio D. Barberis M. Barbero D. Y. Bardin T. Barillari M. Barisonzi T. Barklow N. Barlow B. M. Barnett R. M. Barnett A. Baroncelli G. Barone A. J. Barr F. Barreiro J. Barreiro Guimarães da Costa P. Barrillon R. Bartoldus A. E. Barton V. B Fakultät für Mathematik und Physik Albert-Ludwigs-Universität Freiburg Germany Physikalisches Institut University of Bonn Bonn Germany Homer L. Dodge Department of Physics and Astronomy University of Oklahoma Norman Oklahoma USA Institut de Física d’Altes Energies and Departament de Física de la Universitat Autònoma de Barcelona and ICREA Barcelona Spain LAL Université Paris-Sud and CNRS/IN2P3 Orsay France Section de Physique Université de Genève Geneva Switzerland Institute of Physics Azerbaijan Academy of Sciences Baku Azerbaijan Nikhef National Institute for Subatomic Physics and University of Amsterdam Amsterdam Netherlands Department of Physics Oklahoma State University Stillwater Oklahoma USA Department of Physics and Astronomy Michigan State University East Lansing Michigan USA Department of Physics University of Toronto Toronto Ontario Canada Raymond and Beverly Sackler School of Physics and Astronomy Tel Aviv University Tel Aviv Israel DSM/IRFU (Institut de Recherches sur les Lois Fondamentales de l’Univers) CEA Saclay (Commissariat a l’Energie Atomique) Gif-sur-Yvette France INFN Gruppo Collegato di Udine Italy ICTP Trieste Italy AGH University of Science and Technology Faculty of Physics and Applied Computer Science Krakow Poland Physics Department Brookhaven National Laboratory Upton New York USA Department of Physics Hampton University Hampton Virginia USA Department of Physics Yale University New Haven Connecticut USA Fakultät für Physik Ludwig-Maximilians-Universität München München Germany School of Physics and Astronomy Queen Mary University of London London United Kingdom Particle Physics Department Rutherford Appleton Laboratory Didcot United Kingdom Department of Physics Brandeis University Waltham Massachusetts USA Departamento de Fisica Teorica y del Cosmos and CAFPE Universidad de Granada Granada Spain Albert Einstein Center for Fundamental Physics and Laboratory for High Energy Physics University of Bern Bern Swi

This paper presents a measurement of the W+W− production cross section in pp collisions at s=7 TeV. The leptonic decay channels are analyzed using data corresponding to an integrated luminosity of 4.6 fb−1 collected with the ATLAS detector at the Large Hadron Collider. The W+W− production cross section σ(pp→W+W−+X) is measured to be 51.9±2.0(stat)±3.9(syst)±2.0(lumi) pb, compatible with the Standard Model prediction of 44.7−1.9+2.1 pb. A measurement of the normalized fiducial cross section as a function of the leading lepton transverse momentum is also presented. The reconstructed transverse momentum distribution of the leading lepton is used to extract limits on anomalous WWZ and WWγ couplings.

关键词： COLLISIONS (Nuclear physics) NUCLEAR counters MAGNETIC couplings PHYSICAL measurements LARGE Hadron Collider (France & Switzerland) LEPTONS (Nuclear physics) CROSS sections (Nuclear physics) STANDARD model (Nuclear physics)

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Resource management of enterprise cloud systems using layered queuing and historical performance models

Resource management of enterprise cloud systems using layere...

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IEEE International Symposium on Parallel and Distributed Processing Workshops and Phd Forum (IPDPSW)

作者： David A. Bacigalupo Jano van Hemert Asif Usmani Donna N. Dillenberger Gary B. Wills Stephen A. Jarvis School of Electronics and Computer Science University of Southampton UK Data-Intensive Research Group School of Informatics University of Edinburgh UK BRE Centre of Fire Safety Engineering School of Engineering University of Edinburgh UK IBM Thomas J. Watson Research Center Yorktown Heights NY USA High Performance Systems Group Department of Computer Science University of Warwick UK

ISBN: (纸本)9781424465330

The automatic allocation of enterprise workload to resources can be enhanced by being able to make `what-if' response time predictions, whilst different allocations are being considered. It is important to quantitatively compare the effectiveness of different prediction techniques for use in cloud infrastructures. To help make the comparison of relevance to a wide range of possible cloud environments it is useful to consider the following. 1.) urgent cloud customers such as the emergency services that can demand cloud resources at short notice (e.g. for our FireGrid emergency response software). 2.) dynamic enterprise systems, that must rapidly adapt to frequent changes in workload, system configuration and/or available cloud servers. 3.) The use of the predictions in a coordinated manner by both the cloud infrastructure and cloud customer management systems. 4.) A broad range of criteria for evaluating each technique. However, there have been no previous comparisons meeting these requirements. This paper, meeting the above requirements, quantitatively compares the layered queuing and (¿HYDRA¿) historical techniques - including our initial thoughts on how they could be combined. Supporting results and experiments include the following: i.) defining, investigating and hence providing guidelines on the use of a historical and layered queuing model; ii.) using these guidelines showing that both techniques can make low overhead and typically over 70% accurate predictions, for new server architectures for which only a small number of benchmarks have been run; and iii.) defining and investigating tuning a prediction-based cloud workload and resource management algorithm.

关键词： Resource management Clouds Delay Predictive models computer science Data engineering Emergency services Disaster management Guidelines Quality of service

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Search for charginos nearly mass degenerate with the lightest neutralino based on a disappearing-track signature in pp collisions at (s)=8 TeV with the ATLAS detector

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Physical Review D 2013年第11期88卷 112006-112006页

作者： G. Aad T. Abajyan B. Abbott J. Abdallah S. Abdel Khalek O. Abdinov R. Aben B. Abi M. Abolins O. S. AbouZeid H. Abramowicz H. Abreu Y. Abulaiti B. S. Acharya L. Adamczyk D. L. Adams T. N. Addy J. Adelman S. Adomeit T. Adye S. Aefsky T. Agatonovic-Jovin J. A. Aguilar-Saavedra M. Agustoni S. P. Ahlen A. Ahmad F. Ahmadov M. Ahsan G. Aielli T. P. A. Åkesson G. Akimoto A. V. Akimov M. A. Alam J. Albert S. Albrand M. J. Alconada Verzini M. Aleksa I. N. Aleksandrov F. Alessandria C. Alexa G. Alexander G. Alexandre T. Alexopoulos M. Alhroob M. Aliev G. Alimonti L. Alio J. Alison B. M. M. Allbrooke L. J. Allison P. P. Allport S. E. Allwood-Spiers J. Almond A. Aloisio R. Alon A. Alonso F. Alonso A. Altheimer B. Alvarez Gonzalez M. G. Alviggi K. Amako Y. Amaral Coutinho C. Amelung V. V. Ammosov S. P. Amor Dos Santos A. Amorim S. Amoroso N. Amram G. Amundsen C. Anastopoulos L. S. Ancu N. Andari T. Andeen C. F. Anders G. Anders K. J. Anderson A. Andreazza V. Andrei X. S. Anduaga S. Angelidakis P. Anger A. Angerami F. Anghinolfi A. V. Anisenkov N. Anjos A. Annovi A. Antonaki M. Antonelli A. Antonov J. Antos F. Anulli M. Aoki L. Aperio Bella R. Apolle G. Arabidze I. Aracena Y. Arai A. T. H. Arce S. Arfaoui J-F. Arguin S. Argyropoulos E. Arik M. Arik A. J. Armbruster O. Arnaez V. Arnal O. Arslan A. Artamonov G. Artoni S. Asai N. Asbah S. Ask B. Åsman L. Asquith K. Assamagan R. Astalos A. Astbury M. Atkinson N. B. Atlay B. Auerbach E. Auge K. Augsten M. Aurousseau G. Avolio G. Azuelos Y. Azuma M. A. Baak C. Bacci A. M. Bach H. Bachacou K. Bachas M. Backes M. Backhaus J. Backus Mayes E. Badescu P. Bagiacchi P. Bagnaia Y. Bai D. C. Bailey T. Bain J. T. Baines O. K. Baker S. Baker P. Balek F. Balli E. Banas Sw. Banerjee D. Banfi A. Bangert V. Bansal H. S. Bansil L. Barak S. P. Baranov T. Barber E. L. Barberio D. Barberis M. Barbero D. Y. Bardin T. Barillari M. Barisonzi T. Barklow N. Barlow B. M. Barnett R. M. Barnett A. Baroncelli G. Barone A. J. Barr F. Barreiro J. Barreiro Guimarães da Costa R. Bartoldus A. E. Barton V. Bartsch A. Fakultät für Mathematik und Physik Albert-Ludwigs-Universität Freiburg Germany Physikalisches Institut University of Bonn Bonn Germany Homer L. Dodge Department of Physics and Astronomy University of Oklahoma Norman Oklahoma USA Institut de Física d’Altes Energies and Departament de Física de la Universitat Autònoma de Barcelona Barcelona Spain LAL Université Paris-Sud and CNRS/IN2P3 Orsay France Institute of Physics Azerbaijan Academy of Sciences Baku Azerbaijan Nikhef National Institute for Subatomic Physics and University of Amsterdam Amsterdam Netherlands Department of Physics Oklahoma State University Stillwater Oklahoma USA Department of Physics and Astronomy Michigan State University East Lansing Michigan USA Department of Physics University of Toronto Toronto Ontario Canada Raymond and Beverly Sackler School of Physics and Astronomy Tel Aviv University Tel Aviv Israel DSM/IRFU (Institut de Recherches sur les Lois Fondamentales de l’Univers) CEA Saclay (Commissariat à l’Energie Atomique et aux Energies Alternatives) Gif-sur-Yvette France Department of Physics Stockholm University Sweden The Oskar Klein Centre Stockholm Sweden INFN Gruppo Collegato di Udine Italy ICTP Trieste Italy AGH University of Science and Technology Faculty of Physics and Applied Computer Science Krakow Poland Physics Department Brookhaven National Laboratory Upton New York USA Department of Physics Hampton University Hampton Virginia USA Department of Physics Yale University New Haven Connecticut USA Fakultät für Physik Ludwig-Maximilians-Universität München München Germany Particle Physics Department Rutherford Appleton Laboratory Didcot United Kingdom Department of Physics Brandeis University Waltham Massachusetts USA Vinca Institute of Nuclear Sciences University of Belgrade Belgrade Serbia Departamento de Fisica Teorica y del Cosmos and CAFPE Universidad de Granada Granada Spain Albert Einstein Center for Fundamental Physics and Laboratory for High Energy

A search is presented for direct chargino production based on a disappearing-track signature using 20.3 fb−1 of proton-proton collisions at s=8 TeV collected with the ATLAS experiment at the LHC. In anomaly-mediated supersymmetry breaking (AMSB) models, the lightest chargino is nearly mass degenerate with the lightest neutralino and its lifetime is long enough to be detected in the tracking detectors by identifying decays that result in tracks with no associated hits in the outer region of the tracking system. Some models with supersymmetry also predict charginos with a significant lifetime. This analysis attains sensitivity for charginos with a lifetime between 0.1 and 10 ns, and significantly surpasses the reach of the LEP experiments. No significant excess above the background expectation is observed for candidate tracks with large transverse momentum, and constraints on chargino properties are obtained. In the AMSB scenarios, a chargino mass below 270 GeV is excluded at 95% confidence level.

关键词： NUCLEAR counters CHARGINOS COLLISIONS (Nuclear physics) SUPERSYMMETRY (Physics) NEUTRALINOS

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Search for microscopic black holes in a like-sign dimuon final state using large track multiplicity with the ATLAS detector

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Physical Review D 2013年第7期88卷 072001-072001页

作者： G. Aad T. Abajyan B. Abbott J. Abdallah S. Abdel Khalek O. Abdinov R. Aben B. Abi M. Abolins O. S. AbouZeid H. Abramowicz H. Abreu Y. Abulaiti B. S. Acharya L. Adamczyk D. L. Adams T. N. Addy J. Adelman S. Adomeit T. Adye S. Aefsky T. Agatonovic-Jovin J. A. Aguilar-Saavedra M. Agustoni S. P. Ahlen A. Ahmad F. Ahmadov M. Ahsan G. Aielli T. P. A. Åkesson G. Akimoto A. V. Akimov M. A. Alam J. Albert S. Albrand M. J. Alconada Verzini M. Aleksa I. N. Aleksandrov F. Alessandria C. Alexa G. Alexander G. Alexandre T. Alexopoulos M. Alhroob M. Aliev G. Alimonti L. Alio J. Alison B. M. M. Allbrooke L. J. Allison P. P. Allport S. E. Allwood-Spiers J. Almond A. Aloisio R. Alon A. Alonso F. Alonso A. Altheimer B. Alvarez Gonzalez M. G. Alviggi K. Amako Y. Amaral Coutinho C. Amelung V. V. Ammosov S. P. Amor Dos Santos A. Amorim S. Amoroso N. Amram C. Anastopoulos L. S. Ancu N. Andari T. Andeen C. F. Anders G. Anders K. J. Anderson A. Andreazza V. Andrei X. S. Anduaga S. Angelidakis P. Anger A. Angerami F. Anghinolfi A. V. Anisenkov N. Anjos A. Annovi A. Antonaki M. Antonelli A. Antonov J. Antos F. Anulli M. Aoki L. Aperio Bella R. Apolle G. Arabidze I. Aracena Y. Arai A. T. H. Arce S. Arfaoui J-F. Arguin S. Argyropoulos E. Arik M. Arik A. J. Armbruster O. Arnaez V. Arnal O. Arslan A. Artamonov G. Artoni S. Asai N. Asbah S. Ask B. Åsman L. Asquith K. Assamagan R. Astalos A. Astbury M. Atkinson N. B. Atlay B. Auerbach E. Auge K. Augsten M. Aurousseau G. Avolio D. Axen G. Azuelos Y. Azuma M. A. Baak C. Bacci A. M. Bach H. Bachacou K. Bachas M. Backes M. Backhaus J. Backus Mayes E. Badescu P. Bagiacchi P. Bagnaia Y. Bai D. C. Bailey T. Bain J. T. Baines O. K. Baker S. Baker P. Balek F. Balli E. Banas Sw. Banerjee D. Banfi A. Bangert V. Bansal H. S. Bansil L. Barak S. P. Baranov T. Barber E. L. Barberio D. Barberis M. Barbero D. Y. Bardin T. Barillari M. Barisonzi T. Barklow N. Barlow B. M. Barnett R. M. Barnett A. Baroncelli G. Barone A. J. Barr F. Barreiro J. Barreiro Guimarães da Costa R. Bartoldus A. E. Barton V. Bartsch A. Bas Fakultät für Mathematik und Physik Albert-Ludwigs-Universität Freiburg Germany Physikalisches Institut University of Bonn Bonn Germany Homer L. Dodge Department of Physics and Astronomy University of Oklahoma Norman Oklahoma USA Institut de Física d’Altes Energies and Departament de Física de la Universitat Autònoma de Barcelona Barcelona Spain LAL Université Paris-Sud and CNRS/IN2P3 Orsay France Institute of Physics Azerbaijan Academy of Sciences Baku Azerbaijan Nikhef National Institute for Subatomic Physics and University of Amsterdam Amsterdam Netherlands Department of Physics Oklahoma State University Stillwater Oklahoma USA Department of Physics and Astronomy Michigan State University East Lansing Michigan USA Department of Physics University of Toronto Toronto Ontario Canada Raymond and Beverly Sackler School of Physics and Astronomy Tel Aviv University Tel Aviv Israel DSM/IRFU (Institut de Recherches sur les Lois Fondamentales de l’Univers) CEA Saclay (Commissariat à l’Energie Atomique et aux Energies Alternatives) Gif-sur-Yvette France Department of Physics Stockholm University Stockholm Sweden The Oskar Klein Centre Stockholm Sweden INFN Gruppo Collegato di Udine Trieste Italy ICTP Trieste Italy AGH University of Science and Technology Faculty of Physics and Applied Computer Science Krakow Poland Physics Department Brookhaven National Laboratory Upton New York USA Department of Physics Hampton University Hampton Virginia USA Department of Physics Yale University New Haven Connecticut USA Fakultät für Physik Ludwig-Maximilians-Universität München München Germany Particle Physics Department Rutherford Appleton Laboratory Didcot United Kingdom Department of Physics Brandeis University Waltham Massachusetts USA Vinca Institute of Nuclear Sciences University of Belgrade Belgrade Serbia Departamento de Fisica Teorica y del Cosmos and CAFPE Universidad de Granada Granada Spain Albert Einstein Center for Fundamental Physics and Labora

A search is presented for microscopic black holes in a like-sign dimuon final state in proton–proton collisions at s=8 TeV. The data were collected with the ATLAS detector at the Large Hadron Collider in 2012 and correspond to an integrated luminosity of 20.3 fb−1. Using a high track multiplicity requirement, 0.6±0.2 background events from Standard Model processes are predicted and none observed. This result is interpreted in the context of low-scale gravity models and 95% C.L. lower limits on microscopic black hole masses are set for different model assumptions.

关键词： BLACK holes (Astronomy) MICROSCOPY MUONS PARTICLES (Nuclear physics) -- Multiplicity PROTON-proton interactions LUMINOSITY GRAVITY LARGE Hadron Collider (France & Switzerland)

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Search for nonpointing photons in the diphoton and ETmiss final state in s=7 TeV proton-proton collisions using the ATLAS detector

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Physical Review D 2013年第1期88卷 012001-012001页

作者： G. Aad T. Abajyan B. Abbott J. Abdallah S. Abdel Khalek A. A. Abdelalim O. Abdinov R. Aben B. Abi M. Abolins O. S. AbouZeid H. Abramowicz H. Abreu Y. Abulaiti B. S. Acharya L. Adamczyk D. L. Adams T. N. Addy J. Adelman S. Adomeit T. Adye S. Aefsky J. A. Aguilar-Saavedra M. Agustoni S. P. Ahlen F. Ahles A. Ahmad M. Ahsan G. Aielli T. P. A. Åkesson G. Akimoto A. V. Akimov M. A. Alam J. Albert S. Albrand M. J. Alconada Verzini M. Aleksa I. N. Aleksandrov F. Alessandria C. Alexa G. Alexander G. Alexandre T. Alexopoulos M. Alhroob M. Aliev G. Alimonti J. Alison B. M. M. Allbrooke L. J. Allison P. P. Allport S. E. Allwood-Spiers J. Almond A. Aloisio R. Alon A. Alonso F. Alonso A. Altheimer B. Alvarez Gonzalez M. G. Alviggi K. Amako Y. Amaral Coutinho C. Amelung V. V. Ammosov S. P. Amor Dos Santos A. Amorim S. Amoroso N. Amram C. Anastopoulos L. S. Ancu N. Andari T. Andeen C. F. Anders G. Anders K. J. Anderson A. Andreazza V. Andrei X. S. Anduaga S. Angelidakis P. Anger A. Angerami F. Anghinolfi A. Anisenkov N. Anjos A. Annovi A. Antonaki M. Antonelli A. Antonov J. Antos F. Anulli M. Aoki L. Aperio Bella R. Apolle G. Arabidze I. Aracena Y. Arai A. T. H. Arce S. Arfaoui J.-F. Arguin S. Argyropoulos E. Arik M. Arik A. J. Armbruster O. Arnaez V. Arnal A. Artamonov G. Artoni D. Arutinov S. Asai N. Asbah S. Ask B. Åsman L. Asquith K. Assamagan R. Astalos A. Astbury M. Atkinson B. Auerbach E. Auge K. Augsten M. Aurousseau G. Avolio D. Axen G. Azuelos Y. Azuma M. A. Baak G. Baccaglioni C. Bacci A. M. Bach H. Bachacou K. Bachas M. Backes M. Backhaus J. Backus Mayes E. Badescu P. Bagiacchi P. Bagnaia Y. Bai D. C. Bailey T. Bain J. T. Baines O. K. Baker S. Baker P. Balek F. Balli E. Banas P. Banerjee Sw. Banerjee D. Banfi A. Bangert V. Bansal H. S. Bansil L. Barak S. P. Baranov T. Barber E. L. Barberio D. Barberis M. Barbero D. Y. Bardin T. Barillari M. Barisonzi T. Barklow N. Barlow B. M. Barnett R. M. Barnett A. Baroncelli G. Barone A. J. Barr F. Barreiro J. Barreiro Guimarães da Costa R. Bartoldus A. E. Barton V. Bartsch A. Ba Fakultät für Mathematik und Physik Albert-Ludwigs-Universität Freiburg Germany Physikalisches Institut University of Bonn Bonn Germany Homer L. Dodge Department of Physics and Astronomy University of Oklahoma Norman Oklahoma USA Institut de Física d’Altes Energies and Departament de Física de la Universitat Autònoma de Barcelona and ICREA Barcelona Spain LAL Université Paris-Sud and CNRS/IN2P3 Orsay France Section de Physique Université de Genève Geneva Switzerland Institute of Physics Azerbaijan Academy of Sciences Baku Azerbaijan Nikhef National Institute for Subatomic Physics and University of Amsterdam Amsterdam Netherlands Department of Physics Oklahoma State University Stillwater Oklahoma USA Department of Physics and Astronomy Michigan State University East Lansing Michigan USA Department of Physics University of Toronto Toronto Ontario Canada Raymond and Beverly Sackler School of Physics and Astronomy Tel Aviv University Tel Aviv Israel DSM/IRFU (Institut de Recherches sur les Lois Fondamentales de l’Univers) CEA Saclay (Commissariat à l’Energie Atomique et aux Energies Alternatives) Gif-sur-Yvette France Department of Physics Stockholm University Sweden The Oskar Klein Centre Stockholm Sweden INFN Gruppo Collegato di Udine Italy ICTP Trieste Italy AGH University of Science and Technology Faculty of Physics and Applied Computer Science Krakow Poland Physics Department Brookhaven National Laboratory Upton New York USA Department of Physics Hampton University Hampton Virginia USA Department of Physics Yale University New Haven Connecticut USA Fakultät für Physik Ludwig-Maximilians-Universität München München Germany Particle Physics Department Rutherford Appleton Laboratory Didcot United Kingdom Department of Physics Brandeis University Waltham Massachusetts USA Departamento de Fisica Teorica y del Cosmos and CAFPE Universidad de Granada Granada Spain Albert Einstein Center for Fundamental Physics and Laboratory for High Energy Phys

A search has been performed for photons originating in the decay of a neutral long-lived particle, exploiting the capabilities of the ATLAS electromagnetic calorimeter to make precise measurements of the flight direction of photons, as well as the calorimeter’s excellent time resolution. The search has been made in the diphoton plus missing transverse energy final state, using the full data sample of 4.8 fb−1 of 7 TeV proton-proton collisions collected in 2011 with the ATLAS detector at the LHC. No excess is observed above the background expected from Standard Model processes. The results are used to set exclusion limits in the context of gauge mediated supersymmetry breaking models, with the lightest neutralino being the next-to-lightest supersymmetric particle and decaying with a lifetime in excess of 0.25 ns into a photon and a gravitino.

关键词： Search nonpointing photons diphoton Atlas Collisions atlas Disintegration Searches terminal states Calorimeters Photon detector

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Search for long-lived stopped R-hadrons decaying out of time with pp collisions using the ATLAS detector

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Physical Review D 2013年第11期88卷 112003-112003页

作者： G. Aad T. Abajyan B. Abbott J. Abdallah S. Abdel Khalek O. Abdinov R. Aben B. Abi M. Abolins O. S. AbouZeid H. Abramowicz H. Abreu Y. Abulaiti B. S. Acharya L. Adamczyk D. L. Adams T. N. Addy J. Adelman S. Adomeit T. Adye S. Aefsky T. Agatonovic-Jovin J. A. Aguilar-Saavedra M. Agustoni S. P. Ahlen A. Ahmad F. Ahmadov M. Ahsan G. Aielli T. P. A. Åkesson G. Akimoto A. V. Akimov M. A. Alam J. Albert S. Albrand M. J. Alconada Verzini M. Aleksa I. N. Aleksandrov F. Alessandria C. Alexa G. Alexander G. Alexandre T. Alexopoulos M. Alhroob M. Aliev G. Alimonti L. Alio J. Alison B. M. M. Allbrooke L. J. Allison P. P. Allport S. E. Allwood-Spiers J. Almond A. Aloisio R. Alon A. Alonso F. Alonso A. Altheimer B. Alvarez Gonzalez M. G. Alviggi K. Amako Y. Amaral Coutinho C. Amelung V. V. Ammosov S. P. Amor Dos Santos A. Amorim S. Amoroso N. Amram C. Anastopoulos L. S. Ancu N. Andari T. Andeen C. F. Anders G. Anders K. J. Anderson A. Andreazza V. Andrei X. S. Anduaga S. Angelidakis P. Anger A. Angerami F. Anghinolfi A. V. Anisenkov N. Anjos A. Annovi A. Antonaki M. Antonelli A. Antonov J. Antos F. Anulli M. Aoki L. Aperio Bella R. Apolle G. Arabidze I. Aracena Y. Arai A. T. H. Arce S. Arfaoui J-F. Arguin S. Argyropoulos E. Arik M. Arik A. J. Armbruster O. Arnaez V. Arnal O. Arslan A. Artamonov G. Artoni S. Asai N. Asbah S. Ask B. Åsman L. Asquith K. Assamagan R. Astalos A. Astbury M. Atkinson N. B. Atlay B. Auerbach E. Auge K. Augsten M. Aurousseau G. Avolio D. Axen G. Azuelos Y. Azuma M. A. Baak C. Bacci A. M. Bach H. Bachacou K. Bachas M. Backes M. Backhaus J. Backus Mayes E. Badescu P. Bagiacchi P. Bagnaia Y. Bai D. C. Bailey T. Bain J. T. Baines O. K. Baker S. Baker P. Balek F. Balli E. Banas Sw. Banerjee D. Banfi A. Bangert V. Bansal H. S. Bansil L. Barak S. P. Baranov T. Barber E. L. Barberio D. Barberis M. Barbero D. Y. Bardin T. Barillari M. Barisonzi T. Barklow N. Barlow B. M. Barnett R. M. Barnett A. Baroncelli G. Barone A. J. Barr F. Barreiro J. Barreiro Guimarães da Costa R. Bartoldus A. E. Barton V. Bartsch A. Bas Fakultät für Mathematik und Physik Albert-Ludwigs-Universität Freiburg Germany Physikalisches Institut University of Bonn Bonn Germany Homer L. Dodge Department of Physics and Astronomy University of Oklahoma Norman Oklahoma USA Institut de Física d’Altes Energies and Departament de Física de la Universitat Autònoma de Barcelona Barcelona Spain LAL Université Paris-Sud and CNRS/IN2P3 Orsay France Institute of Physics Azerbaijan Academy of Sciences Baku Azerbaijan Nikhef National Institute for Subatomic Physics and University of Amsterdam Amsterdam Netherlands Department of Physics Oklahoma State University Stillwater Oklahoma USA Department of Physics and Astronomy Michigan State University East Lansing Michigan USA Department of Physics University of Toronto Toronto Ontario Canada Raymond and Beverly Sackler School of Physics and Astronomy Tel Aviv University Tel Aviv Israel DSM/IRFU (Institut de Recherches sur les Lois Fondamentales de l’Univers) CEA Saclay (Commissariat à l’Energie Atomique et aux Energies Alternatives) Gif-sur-Yvette France Department of Physics Stockholm University Sweden The Oskar Klein Centre Stockholm Sweden INFN Gruppo Collegato di Udine Italy ICTP Trieste Italy AGH University of Science and Technology Faculty of Physics and Applied Computer Science Krakow Poland Physics Department Brookhaven National Laboratory Upton New York USA Department of Physics Hampton University Hampton Virginia USA Department of Physics Yale University New Haven Connecticut USA Fakultät für Physik Ludwig-Maximilians-Universität München München Germany Particle Physics Department Rutherford Appleton Laboratory Didcot United Kingdom Department of Physics Brandeis University Waltham Massachusetts USA Vinca Institute of Nuclear Sciences University of Belgrade Belgrade Serbia Departamento de Fisica Teorica y del Cosmos and CAFPE Universidad de Granada Granada Spain Albert Einstein Center for Fundamental Physics and Laboratory for High Energy

An updated search is performed for gluino, top squark, or bottom squark R-hadrons that have come to rest within the ATLAS calorimeter, and decay at some later time to hadronic jets and a neutralino, using 5.0 and 22.9 fb−1 of pp collisions at 7 and 8 TeV, respectively. Candidate decay events are triggered in selected empty bunch crossings of the LHC in order to remove pp collision backgrounds. Selections based on jet shape and muon system activity are applied to discriminate signal events from cosmic ray and beam-halo muon backgrounds. In the absence of an excess of events, improved limits are set on gluino, stop, and sbottom masses for different decays, lifetimes, and neutralino masses. With a neutralino of mass 100 GeV, the analysis excludes gluinos with mass below 832 GeV (with an expected lower limit of 731 GeV), for a gluino lifetime between 10 μs and 1000 s in the generic R-hadron model with equal branching ratios for decays to qq¯χ˜0 and gχ˜0. Under the same assumptions for the neutralino mass and squark lifetime, top squarks and bottom squarks in the Regge R-hadron model are excluded with masses below 379 and 344 GeV, respectively.

关键词： NUCLEAR counters HADRONS -- Decay COLLISIONS (Nuclear physics) CALORIMETRY MUONS

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