Measurements of four-lepton production in $pp$ collisions at $\sqrt{s}=$ 8 TeV with the ATLAS detector

Abstract

The four-lepton ($4\ell$, $\ell =e,\mu$) production cross section is measured in the mass range from 80 to 1000 GeV using 20.3 fb${}^{-1}$ of data in $pp$ collisions at $\sqrt{s}=8$ TeV collected with the ATLAS detector at the LHC. The $4\ell$ events are produced in the decays of resonant $Z$ and Higgs bosons and the non-resonant $ZZ$ continuum originating from $q\bar{q}$, $gg$, and $qg$ initial states. A total of 476 signal candidate events are observed with a background expectation of $26.2\pm 3.6$ events, enabling the measurement of the integrated cross section and the differential cross section as a function of the invariant mass and transverse momentum of the four-lepton system. In the mass range above $180$ GeV, assuming the theoretical constraint on the $q\bar{q}$ production cross section calculated with perturbative NNLO QCD and NLO electroweak corrections, the signal strength of the gluon-fusion component relative to its leading-order prediction is determined to be ${\mu }_{gg}=2.4\pm 1.0(stat.)\pm 0.5(syst.)\pm 0.8(theory)$.

20 pages plus author list + cover pages (37 pages total), 5 figures, 6 tables, submitted to Physics Letters B, All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2014-15/

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