Measurements of Z γ and Z γγ production in pp collisions at ffiffi s p = 8 TeV with the ATLAS detector

This document is made available in accordance with publisher policies and may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the URL above for details on accessing the published version. Copyright and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable, the material made available in SRO has been checked for eligibility before being made available. Copies of full text items generally can be reproduced, displayed or performed and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Measurements of Zγ and Zγγ production in pp collisions at ffiffi s p =8 TeV with the ATLAS detector G. Aad et al. The production of Z bosons with one or two isolated high-energy photons is studied using pp collisions at ffiffi ffi s p ¼ 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 þ e − , μ þ μ − , ν¯ ν) 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 E T > 250 GeV from l þ l − γ events and with E T > 400 GeV from ν¯ νγ events are used to search for anomalous triple gauge-boson couplings ZZγ and Zγγ. The yields of events with diphoton invariant mass m γγ > 200 GeV from l þ l − γγ events and with m γγ > 300 GeV from ν¯ νγγ events are used to search for anomalous quartic gauge-boson couplings ZZγγ and Zγγγ. No …

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