Measurements of Higgs boson production and couplings in the four-lepton channel in $pp$ collisions at center-of-mass energies of 7 and 8 TeV with the ATLAS detector

Abstract

The final ATLAS Run 1 measurements of Higgs boson production and couplings in the decay channel $H\to Z{Z}^{\ast }\to {\ell }^{+}{\ell }^{-}{\ell }^{{}^{\prime }+}{\ell }^{{}^{\prime }-}$, where $\ell ,{\ell }^{{}^{\prime }}=e$ or $\mu$, are presented. These measurements were performed using $pp$ collision data corresponding to integrated luminosities of 4.5 fb${}^{-1}$ and 20.3 fb${}^{-1}$ at center-of-mass energies of 7 TeV and 8 TeV, respectively, recorded with the ATLAS detector at the LHC. The $H\to Z{Z}^{\ast }\to 4\ell$ signal is observed with a significance of 8.1 standard deviations, with an expectation of 6.2 standard deviations, at $m_H$ = 125.36 GeV, the combined ATLAS measurement of the Higgs boson mass from the $H\to \gamma \gamma$ and $H\to Z{Z}^{\ast }\to 4\ell$ channels. The production rate relative to the Standard Model expectation, the signal strength, is measured in four different production categories in the $H\to Z{Z}^{\ast }\to 4\ell$ channel. The measured signal strength, at this mass, and with all categories combined, is 1.44 ${}_{-0.33}^{+0.40}$. The signal strength for Higgs boson production in gluon fusion or in association with $t\bar{t}$ or $b\bar{b}$ pairs is found to be 1.7 ${}_{-0.4}^{+0.5}$, while the signal strength for vector-boson fusion combined with $WH/ZH$ associated production is found to be 0.3 ${}_{-0.9}^{+1.6}$.

40 pages plus author list + cover pages (54 pages total), 21 figures, 12 tables, submitted to Physical Review D, All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HIGG-2013-21/

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