Measurements of Zγ and Zγγ production in pp collisions at √s = 8 TeV with the ATLAS detector
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<sup>-1</sup> collected by the ATLAS detector during the 2012 LHC data taking. The Zγ and Zγγ produ...
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| Autores principales: | , , , , , , |
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| Formato: | Articulo |
| Lenguaje: | Inglés |
| Publicado: |
2016
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| Materias: | |
| Acceso en línea: | http://sedici.unlp.edu.ar/handle/10915/86795 |
| Aporte de: |
| Sumario: | 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<sup>-1</sup> collected by the ATLAS detector during the 2012 LHC data taking. The Zγ and Zγγ production cross sections are measured with leptonic (e<sup>+</sup>e<sup>-</sup>, μ<sup>+</sup>μ<sup>-</sup>, 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 E<sub>T</sub>>250 GeV from ℓ<sup>+</sup>ℓ<sup>-</sup>γ events and with E<sub>T</sub>>400 GeV from νν¯γ events are used to search for anomalous triple gauge-boson couplings ZZγ and Zγγ. The yields of events with diphoton invariant mass m<sub>γγ</sub>>200 GeV from ℓ<sup>+</sup>ℓ<sup>-</sup>γγ events and with m<sub>γγ</sub>>300 GeV from νν¯γγ 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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