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Measurements of Zγ and Zγγ production in pp collisions at s =8 TeV with the ATLAS detector

  • Author(s): Aad, G
  • Abbott, B
  • Abdallah, J
  • Abdinov, O
  • Abeloos, B
  • Aben, R
  • Abolins, M
  • Abouzeid, OS
  • Abraham, NL
  • Abramowicz, H
  • Abreu, H
  • Abreu, R
  • Abulaiti, Y
  • Acharya, BS
  • Adamczyk, L
  • Adams, DL
  • Adelman, J
  • Adomeit, S
  • Adye, T
  • Affolder, AA
  • Agatonovic-Jovin, T
  • Agricola, J
  • Aguilar-Saavedra, JA
  • Ahlen, SP
  • Ahmadov, F
  • Aielli, G
  • Akerstedt, H
  • Åkesson, TPA
  • Akimov, AV
  • Alberghi, GL
  • Albert, J
  • Albrand, S
  • Alconada Verzini, MJ
  • Aleksa, M
  • Aleksandrov, IN
  • Alexa, C
  • Alexander, G
  • Alexopoulos, T
  • Alhroob, M
  • Aliev, M
  • Alimonti, G
  • Alison, J
  • Alkire, SP
  • Allbrooke, BMM
  • Allen, BW
  • Allport, PP
  • Aloisio, A
  • Alonso, A
  • Alonso, F
  • Alpigiani, C
  • Alvarez Gonzalez, B
  • Álvarez Piqueras, D
  • Alviggi, MG
  • Amadio, BT
  • Amako, K
  • Amaral Coutinho, Y
  • Amelung, C
  • Amidei, D
  • Amor Dos Santos, SP
  • Amorim, A
  • Amoroso, S
  • Amram, N
  • Amundsen, G
  • Anastopoulos, C
  • Ancu, LS
  • Andari, N
  • Andeen, T
  • Anders, CF
  • Anders, G
  • Anders, JK
  • Anderson, KJ
  • Andreazza, A
  • Andrei, V
  • Angelidakis, S
  • Angelozzi, I
  • Anger, P
  • Angerami, A
  • Anghinolfi, F
  • Anisenkov, AV
  • Anjos, N
  • Annovi, A
  • Antonelli, M
  • Antonov, A
  • Antos, J
  • Anulli, F
  • Aoki, M
  • Aperio Bella, L
  • Arabidze, G
  • Arai, Y
  • Araque, JP
  • Arce, ATH
  • Arduh, FA
  • Arguin, JF
  • Argyropoulos, S
  • Arik, M
  • Armbruster, AJ
  • Armitage, LJ
  • Arnaez, O
  • Arnold, H
  • Arratia, M
  • et al.
Abstract

The production of Z bosons with one or two isolated high-energy photons is studied using pp collisions at s=8 TeV. The analyses use a data sample with an integrated luminosity of 20.3 fb-1 collected by the ATLAS detector during the 2012 LHC data taking. The Zγ and Zγγ production cross sections are measured with leptonic (e+e-, μ+μ-, νν) decays of the Z boson, in extended fiducial regions defined in terms of the lepton and photon acceptance. They are then compared to cross-section predictions from the Standard Model, where the sources of the photons are radiation off initial-state quarks and radiative Z-boson decay to charged leptons, and from fragmentation of final-state quarks and gluons into photons. The yields of events with photon transverse energy ET>250 GeV from +-γ events and with ET>400 GeV from ννγ events are used to search for anomalous triple gauge-boson couplings ZZγ and Zγγ. The yields of events with diphoton invariant mass mγγ>200 GeV from +-γγ events and with mγγ>300 GeV from ννγγ events are used to search for anomalous quartic gauge-boson couplings ZZγγ and Zγγγ. No deviations from Standard Model predictions are observed and limits are placed on parameters used to describe anomalous triple and quartic gauge-boson couplings.

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