Measurement of the 4l Cross Section at the Z Resonance and Determination of the Branching Fraction of Z->4l in pp Collisions at sqrt(s) = 7 and 8 TeV with ATLAS

Abstract

Measurements of four-lepton (4$\ell$, $\ell =e,\mu$) production cross sections at the $Z$ resonance in $pp$ collisions at the LHC with the ATLAS detector are presented. For dilepton and four-lepton invariant mass region $m_{{\ell }^{+}{\ell }^{-}}>5$ GeV and $80<m_{4\ell }<100$ GeV, the measured cross sections are $76\pm 18\text{ (stat) }\pm 4\text{ (syst) }\pm 1.4\text{ (lumi) }$ fb and $107\pm 9\text{ (stat) }\pm 4\text{ (syst) }\pm 3.0\text{ (lumi) }$ fb at $\sqrt{s}$ = 7 and 8 TeV, respectively. By subtracting the non-resonant 4$\ell$ production contributions and normalizing with $Z\to {\mu }^{+}{\mu }^{-}$ events, the branching fraction for the $Z$ boson decay to $4\ell$ is determined to be $\left(3.20\pm 0.25\text{ (stat)}\pm 0.13\text{ (syst)}\right)\times 10^{-6}$, consistent with the Standard Model prediction.

6 pages plus author list (20 pages total), 2 figures, 1 table, submitted to PRL, All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2013-08/

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