Abstract

The ATLAS collaboration has carried a set of measurements that provide stringent tests of the electroweak sector of Standard Model, specifically on di- and multiboson production cross sections and on triple and quartic gauge-boson couplings. Such measurements include cross sections for WV (V=W or Z) production in the leptonic or semileptonic channels, the production of a W or Z boson in association with photons, a Z boson in the vector-boson fusion channel and two same-charge W bosons in the vectorboson scattering channel. These measurements are compared to (N)NLO predictions of the Standard Model and provide model-independent constraints on new physics, by setting limits on anomalous gauge-boson couplings.An analysis of the inclusive four-lepton lineshape has been carried out in the mass range from 80 to 1000 GeV, where several distinct physics processes give rise to the production of 4-lepton final state, namely the single Z resonant processes, the Higgs production at 125 GeV, as well as continuum ZZ production processes with qq and gg initial states.

Highlights

  • Electroweak (EW) precision measurements at LHC provide a good way to test the expectations of the Standard Model in the EW sector

  • Since no significant differences between measurement and expectation are found, limits where set on anomalous quartic gauge couplings

  • W√ Z and WW decaying leptonically and semi-leptonically were compared to theory predictions at s = 8 TeV and no deviations were found to the Standard Model√expectation

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Summary

Introduction

Electroweak (EW) precision measurements at LHC provide a good way to test the expectations of the Standard Model in the EW sector. Many diboson processes play an important background role for other analyses like measurements of Higgs boson properties or searches for signatures beyond the Standard Model. Deviations from SM gauge interactions, like anomalous triple gauge couplings (aTGCs), could lead to changes in the production cross section, especially in the high boson pair mass range. One can search for anomalous couplings, and the expected triple and quartic gauge coupling can be studied at proton proton collisions at the LHC like Vector Boson. Measuring the VBS cross section is a good way to probe EW symmetry breaking.

Experimental Setup and Physics Object Definitions
Wγ and Zγ cross section measurement
Measurement of four lepton production
Measurement of electroweak production of Z boson in association with two jets
Evidence of Wγγ production
Findings
Conclusion and Outlook
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