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Measurements of $Z\gamma$ and $Z\gamma\gamma$ production in $pp$ collisions at $\sqrt{s}=$ 8 TeV with the ATLAS detector

The collaboration
Phys.Rev. D93 (2016) 112002, 2016

Abstract (data abstract)
CERN-LHC. The production of $Z$ bosons with one or two isolated high-energy photons is studied using $pp$ collisions at $\sqrt{s}$ = 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 $Z\gamma$ and $Z\gamma\gamma$ production cross sections are measured with leptonic ($e^{+}e^{-}$, $\mu^{+}\mu^{-}$, $\nu\bar{\nu}$) 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 $E_{\mathrm{T}} >$ 250 GeV from $\ell^{+}\ell^{-}\gamma$ events and with $E_{\mathrm{T}} >$ 400 GeV from $\nu\bar{\nu}\gamma$ events are used to search for anomalous triple gauge-boson couplings $ZZ\gamma$ and $Z\gamma\gamma$. The yields of events with diphoton invariant mass $m_{\gamma\gamma} >$ 200 GeV from $\ell^{+}\ell^{-}\gamma\gamma$ events and with $m_{\gamma\gamma} >$ 300 GeV from $\nu\bar{\nu}\gamma\gamma$ events are used to search for anomalous quartic gauge-boson couplings $ZZ\gamma\gamma$ and $Z\gamma\gamma\gamma$. No deviations from Standard Model predictions are observed and limits are placed on parameters used to describe anomalous triple and quartic gauge-boson couplings.

• #### Table 1

Data from Table 8 and Table 9

10.17182/hepdata.72823.v1/t1

Measured integrated cross sections for the $Z\gamma$ process for charged lepton final states at $\sqrt{s} = 8$ TeV in the...

• #### Table 2

Data from Table 8 and Table 9

10.17182/hepdata.72823.v1/t2

Measured integrated cross sections for the $Z\gamma$ process for neutrino final states at $\sqrt{s} = 8$ TeV in the extended...

• #### Table 3

Data from Table 8 and Table 9

10.17182/hepdata.72823.v1/t3

Measured integrated cross sections for the $Z\gamma\gamma$ process for charged lepton final states at $\sqrt{s} = 8$ TeV in the...

• #### Table 4

Data from Table 8 and Table 9

10.17182/hepdata.72823.v1/t4

Measured integrated cross sections for the $Z\gamma\gamma$ process for neutrino final state at $\sqrt{s} = 8$ TeV in the extended...

• #### Table 5

Data from Figure 7

10.17182/hepdata.72823.v1/t5

• #### Table 7

Data from Figure 8

10.17182/hepdata.72823.v1/t7

• #### Table 9

Data from Figure 9

10.17182/hepdata.72823.v1/t9

• #### Table 11

Data from Figure 10

10.17182/hepdata.72823.v1/t11

The cross sections as a function of $N_{\mathrm{jets}}$ for the $pp \rightarrow \ell^{+}\ell^{-}\gamma$ process in the extended fiducial region. The...