Accelerator Neutrinos

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Measurement of Z boson production in Pb-Pb collisions at √SNN = 2.76 TeV with the ATLAS detector

Physical Review Letters 110:2 (2013) 022301-1-022301-18

Authors:

G Aad, T Abajyan, B Abbott, J Abdallah, S Abdel Khalek, AA Abdelalim, O Abdinov, R Aben, B Abi, M Abolins, OS Abou Zeid, H Abramowicz, H Abreu, BS Acharya, L Adamczyk, DL Adams, TN Addy, J Adelman, S Adomeit, P Adragna, T Adye, S Aefsky, JA Aguilar-Saavedra, M Agustoni, M Aharrouche, SP Ahlen, F Ahles, A Ahmad, M Ahsan, G Aielli, T Akdogan, TPA Åkesson, G Akimoto, AV Akimov, MS Alam, MA Alam, J Albert, S Albrand, M Aleksa, IN Aleksandrov, F Alessandria, C Alexa, G Alexander, G Alexandre, T Alexopoulos, M Alhroob, M Aliev, G Alimonti, J Alison, BMM Allbrooke, PP Allport, SE Allwood-Spiers, J Almond, A Aloisio, R Alon, A Alonso, F Alonso, A Altheimer, B Alvarez Gonzalez, MG Alviggi, K Amako, C Amelung, VV Ammosov, SP Amor Dos Santos, A Amorim, N Amram, C Anastopoulos, LS Ancu, N Andari, T Andeen, CF Anders, G Anders, KJ Anderson, A Andreazza, V Andrei, ML Andrieux, XS Anduaga, 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, ATH Arce, S Arfaoui, JF Arguin, E Arik, M Arik

Abstract:

The ATLAS experiment has observed 1995 Z boson candidates in data corresponding to 0:15 nb-1 of integrated luminosity obtained in the 2011 LHC Pb + Pb run at √SNN = 2.76 TeV. The Z bosons are reconstructed via dielectron and dimuon decay channels, with a background contamination of less than 3%. Results from the two channels are consistent and are combined. Within the statistical and systematic uncertainties, the per-event Z boson yield is proportional to the number of binary collisions estimated by the Glauber model. The elliptic anisotropy of the azimuthal distribution of the Z boson with respect to the event plane is found to be consistent with zero.
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Measurement of isolated-photon pair production in pp collisions at √s=7TeV with the ATLAS detector

Journal of High Energy Physics 2013:1 (2013)

Authors:

G Aad, T Abajyan, B Abbott, J Abdallah, SA Khalek, AA Abdelalim, O Abdinov, R Aben, B Abi, M Abolins, OS Abouzeid, H Abramowicz, H Abreu, BS Acharya, L Adamczyk, DL Adams, TN Addy, J Adelman, S Adomeit, P Adragna, T Adye, S Aefsky, JA Aguilar-Saavedra, M Agustoni, M Aharrouche, SP Ahlen, F Ahles, A Ahmad, M Ahsan, G Aielli, TPA Åkesson, G Akimoto, AV Akimov, MS Alam, MA Alam, J Albert, S Albrand, M Aleksa, IN Aleksandrov, F Alessandria, C Alexa, G Alexander, G Alexandre, T Alexopoulos, M Alhroob, M Aliev, G Alimonti, J Alison, BMM Allbrooke, PP Allport, SE Allwood-Spiers, J Almond, A Aloisio, R Alon, A Alonso, F Alonso, A Altheimer, BA Gonzalez, MG Alviggi, K Amako, C Amelung, VV Ammosov, SP Amor Dos Santos, A Amorim, N Amram, C Anastopoulos, LS Ancu, N Andari, T Andeen, CF Anders, G Anders, KJ Anderson, A Andreazza, V Andrei, ML Andrieux, XS 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, ATH Arce, S Arfaoui, JF Arguin, S Argyropoulos, E Arik

Abstract:

The ATLAS experiment at the LHC has measured the production cross section of events with two isolated photons in the final state, in proton-proton collisions at √s=7TeV . The full data set collected in 2011, corresponding to an integrated luminosity of 4.9 fb-1, is used. The amount of background, from hadronic jets and isolated electrons, is estimated with data-driven techniques and subtracted. The total cross section, for two isolated photons with transverse energies above 25 GeV and 22 GeV respectively, in the acceptance of the electromagnetic calorimeter (|η| < 1.37 and 1.52 < |η| < 2.37) and with an angular separation ΔR > 0.4, is 44.0-4.2+3.2 pb. The differential cross sections as a function of the di-photon invariant mass, transverse momentum, azimuthal separation, and cosine of the polar angle of the largest transverse energy photon in the Collins-Soper di-photon rest frame are also measured. The results are compared to the prediction of leading-order parton-shower and next-to-leading-order and next-to-next-to-leading-order parton-level generators.[Figure not available: see fulltext.] © 2013 CERN for the benefit of the ATLAS collaboration.
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Measurement of the production cross section of jets in association with a Z boson in pp collisions at √s=7 TeV with the ATLAS detector

Journal of High Energy Physics 2013:7 (2013)

Authors:

G Aad, T Abajyan, B Abbott, J Abdallah, S Abdel Khalek, AA Abdelalim, O Abdinov, R Aben, B Abi, M Abolins, OS Abouzeid, H Abramowicz, H Abreu, Y Abulaiti, BS Acharya, L Adamczyk, DL Adams, TN Addy, J Adelman, S Adomeit, T Adye, S Aefsky, JA Aguilar-Saavedra, M Agustoni, SP Ahlen, F Ahles, A Ahmad, M Ahsan, G Aielli, TPA Åkesson, G Akimoto, AV Akimov, MA Alam, J Albert, S Albrand, M Aleksa, IN Aleksandrov, F Alessandria, C Alexa, G Alexander, G Alexandre, T Alexopoulos, M Alhroob, M Aliev, G Alimonti, J Alison, BMM Allbrooke, LJ Allison, PP Allport, SE Allwood-Spiers, J Almond, A Aloisio, R Alon, A Alonso, F Alonso, A Altheimer, B Alvarez Gonzalez, MG Alviggi, K Amako, C Amelung, VV Ammosov, SP Amor Dos Santos, A Amorim, S Amoroso, N Amram, C Anastopoulos, LS Ancu, N Andari, T Andeen, CF Anders, G Anders, KJ Anderson, A Andreazza, V Andrei, XS 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, ATH Arce, S Arfaoui, JF Arguin, S Argyropoulos, E Arik, M Arik, AJ Armbruster

Abstract:

Measurements of the production of jets of particles in association with a Z boson in pp collisions at √s=7 TeV are presented, using data corresponding to an integrated luminosity of 4.6 fb-1 collected by the ATLAS experiment at the Large Hadron Collider. Inclusive and differential jet cross sections in Z events, with Z decaying into electron or muon pairs, are measured for jets with transverse momentum p T > 30 GeV and rapidity |y| < 4.4. The results are compared to next-to-leading-order perturbative QCD calculations, and to predictions from different Monte Carlo generators based on leading-order and next-to-leading-order matrix elements supplemented by parton showers. [Figure not available: see fulltext.] © 2013 CERN for the benefit of the ATLAS collaboration.
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Publisher’s Note: T2K neutrino flux prediction [Phys. Rev. D 87, 012001 (2013)]

Physical Review D American Physical Society (APS) 87:1 (2013) 019902

Authors:

K Abe, N Abgrall, H Aihara, T Akiri, JB Albert, C Andreopoulos, S Aoki, A Ariga, T Ariga, S Assylbekov, D Autiero, M Barbi, GJ Barker, G Barr, M Bass, M Batkiewicz, F Bay, SW Bentham, V Berardi, BE Berger, S Berkman, I Bertram, D Beznosko, S Bhadra, FDM Blaszczyk, A Blondel, C Bojechko, S Boyd, A Bravar, C Bronner, DG Brook-Roberge, N Buchanan, RG Calland, J Caravaca Rodriguez, SL Cartwright, R Castillo, M-G Catanesi, A Cervera, D Cherdack, G Christodoulou, A Clifton, J Coleman, SJ Coleman, G Collazuol, K Connolly, A Curioni, A Dabrowska, I Danko, R Das, S Davis, M Day, JPAM de Andre, P de Perio, G De Rosa, T Dealtry, C Densham, F Di Lodovico, S Di Luise, J Dobson, T Duboyski, F Dufour, J Dumarchez, S Dytman, M Dziewiecki, M Dziomba, S Emery, A Ereditato, L Escudero, LS Esposito, AJ Finch, E Frank, M Friend, Y Fujii, Y Fukuda, V Galymov, A Gaudin, S Giffin, C Giganti, K Gilje, T Golan, JJ Gomez-Cadenas, M Gonin, N Grant, D Gudin, P Guzowski, DR Hadley, A Haesler, MD Haigh, D Hansen, T Hara, M Hartz, T Hasegawa, NC Hastings, Y Hayato, C Hearty, RL Helmer, J Hignight, A Hillairet, A Himmel, T Hiraki, J Holeczek, S Horikawa, K Huang, A Hyndman, AK Ichikawa, K Ieki, M Ieva, M Ikeda, J Imber, J Insler, T Ishida, T Ishii, SJ Ives, K Iyogi, A Izmaylov, B Jamieson, RA Johnson, JH Jo, P Jonsson, KK Joo, GV Jover-Manas, CK Jung, H Kaji, T Kajita, H Kakuno, J Kameda, Y Kanazawa, D Karlen, I Karpikov, E Kearns, M Khabibullin, F Khanam, A Khotjantsev, D Kielczewska, T Kikawa, A Kilinski, JY Kim, J Kim, SB Kim, B Kirby, J Kisiel, P Kitching, T Kobayashi, G Kogan, A Konaka, LL Kormos, A Korzenev, K Koseki, Y Koshio, K Kowalik, I Kreslo, W Kropp, H Kubo, Y Kudenko, S Kumaratunga, R Kurjata, T Kutter, J Lagoda, K Laihem, A Laing, M Laveder, M Lawe, KP Lee, C Licciardi, IT Lim, T Lindner, C Lister, RP Litchfield, A Longhin, GD Lopez, L Ludovici, M Macaire, L Magaletti, K Mahn, M Malek, S Manly, A Marchionni, AD Marino, J Marteau, JF Martin, T Maruyama, J Marzec, P Masliah, EL Mathie, C Matsumura, K Matsuoka, V Matveev, K Mavrokoridis, E Mazzucato, N McCauley, KS McFarland, C McGrew, T McLachlan, M Messina, C Metelko, M Mezzetto, P Mijakowski, CA Miller, A Minamino, O Mineev, S Mine, A Missert, M Miura, L Monfregola, S Moriyama, Th A Mueller, A Murakami, M Murdoch, S Murphy, J Myslik, T Nagasaki, T Nakadaira, M Nakahata, T Nakai, K Nakajima, K Nakamura, S Nakayama, T Nakaya, K Nakayoshi, D Naples, TC Nicholls, C Nielsen, K Nishikawa, Y Nishimura, HM O’Keeffe, Y Obayashi, R Ohta, K Okumura, W Oryszczak, SM Oser, M Otani, RA Owen, Y Oyama, MY Pac, V Palladino, V Paolone, D Payne, GF Pearce, O Perevozchikov, JD Perkin, ES Pinzon Guerra, P Plonski, E Poplawska, B Popov, M Posiadala, J-M Poutissou, R Poutissou, P Przewlocki, B Quilain, E Radicioni, PN Ratoff, M Ravonel, MA Rayner, M Reeves, E Reinherz-Aronis, F Retiere, PA Rodrigues, E Rondio, B Rossi, S Roth, A Rubbia, D Ruterbories, R Sacco, K Sakashita, F Sánchez, E Scantamburlo, K Scholberg, J Schwehr, M Scott, DI Scully, Y Seiya, T Sekiguchi, H Sekiya, M Shibata, M Shiozawa, S Short, Y Shustrov, P Sinclair, B Smith, RJ Smith, M Smy, JT Sobczyk, H Sobel, M Sorel, L Southwell, P Stamoulis, J Steinmann, B Still, R Sulej, A Suzuki, K Suzuki, SY Suzuki, Y Suzuki, T Szeglowski, M Szeptycka, R Tacik, M Tada, S Takahashi, A Takeda, Y Takeuchi, HA Tanaka, M Tanaka, MM Tanaka, IJ Taylor, D Terhorst, R Terri, LF Thompson, A Thorley, S Tobayama, W Toki, T Tomura, Y Totsuka, C Touramanis, T Tsukamoto, M Tzanov, Y Uchida, K Ueno, A Vacheret, M Vagins, G Vasseur, T Wachala, AV Waldron, CW Walter, J Wang, D Wark, MO Wascko, A Weber, R Wendell, G Wikström, RJ Wilkes, MJ Wilking, C Wilkinson, Z Williamson, JR Wilson, RJ Wilson, T Wongjirad, Y Yamada, K Yamamoto, C Yanagisawa, T Yano, S Yen, N Yershov, M Yokoyama, T Yuan, A Zalewska, L Zambelli, K Zaremba, M Ziembicki, ED Zimmerman, M Zito, J Żmuda
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Search for charged Higgs bosons through the violation of lepton universality in tt events using pp collision data at √S=7 TeV with the ATLAS experiment

Journal of High Energy Physics 2013:3 (2013)

Authors:

G Aad, T Abajyan, B Abbott, J Abdallah, SA Khalek, AA Abdelalim, O Abdinov, R Aben, B Abi, M Abolins, OS Abouzeid, H Abramowicz, H Abreu, BS Acharya, L Adamczyk, DL Adams, TN Addy, J Adelman, S Adomeit, P Adragna, T Adye, S Aefsky, JA Aguilar-Saavedra, M Agustoni, M Aharrouche, SP Ahlen, F Ahles, A Ahmad, M Ahsan, G Aielli, TPA Åkesson, G Akimoto, AV Akimov, MA Alam, J Albert, S Albrand, M Aleksa, IN Aleksandrov, F Alessandria, C Alexa, G Alexander, G Alexandre, T Alexopoulos, M Alhroob, M Aliev, G Alimonti, J Alison, BMM Allbrooke, PP Allport, SE Allwood-Spiers, J Almond, A Aloisio, R Alon, A Alonso, F Alonso, A Altheimer, BA Joffe, MG Alviggi, K Amako, C Amelung, VV Ammosov, SP Amor Dos Santos, A Amorim, N Amram, C Anastopoulos, LS Ancu, N Andari, T Andeen, CF Anders, G Anders, KJ Anderson, A Andreazza, V Andrei, ML Andrieux, XS 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, ATH Arce, S Arfaoui, JF Arguin, S Argyropoulos, E Arik, M Arik

Abstract:

In several extensions of the Standard Model, the top quark can decay into a bottom quark and a light charged Higgs boson H +, t → bH +, in addition to the Standard Model decay t → bW. Since W bosons decay to the three lepton generations equally, while H + maypredominantlydecayinto τν, charged Higgs bosons can be searched for using the violation of lepton universality in top quark decays. The analysis in this paper is based on 4.6 fb-1 of proton-proton collision data at √s=7 TeV collected by the ATLAS experiment at the Large Hadron Collider. Signatures containing leptons (e or μ) and/or a hadronically decaying τ (τ had) are used. Event yield ratios between e + τ had and e + μ, as well as between μ + τ had andμ + e, final states are measured in the data and compared to predictions from simulations. This ratio-based method reduces the impact of systematic uncertainties in the analysis. No significant deviation from the Standard Model predictions is observed. With the assumption that the branching fraction ℬ (H + → τν) is 100%, upper limits in the range 3.2%-4.4% can be placed on the branching fraction ℬ (t → bH +) for charged Higgs boson masses m H+ in the range 90-140 GeV. After combination with results from a search for charged Higgs bosons in t\overline{t} decays using the τ had + jets final state, upper limits on ℬ (t → bH +) can be set in the range 0.8%-3.4%, for m H+ in the range 90-160 GeV.[Figure not available: see fulltext.] © 2013 Cern for the benefit of the ATLAS collaboration.
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