| Přispěvatelé: |
Aad, G, Aloisio, Alberto, Alviggi, Mariagrazia, Canale, Vincenzo, DELLA VOLPE, Domenico, Merola, Leonardo, Conventi, Francesco, DELLA PIETRA, Massimo, Perrella, Sabrina, Rossi, Elvira, Cirotto, Francesco, SANCHEZ PINEDA, ARTURO RODOLFO, Carlino, Gianpaolo, DE ASMUNDIS, Riccardo, DI DONATO, Camilla, Doria, Alessandra, Iengo, Paolo, Izzo, Vincenzo, Sekhniaidze, Givi, Et, A. l. |
| Popis: |
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. © 2016 CERN, for the ATLAS Collaboration. |
