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

Aad, G. and Abbott, B. and Abdallah, J. and Khalek, S. A. and Abdinov, O. and Krasznahorkay, Attila and Nagai, Yoshikazu and Pásztor, Gabriella and Tóth, József (2015) Measurements of Higgs boson production and couplings in the four-lepton channel in pp collisions at center-of-mass energies of 7 and 8TeV with the ATLAS detector. PHYSICAL REVIEW D, 91 (1). ISSN 2470-0010

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Abstract

The final ATLAS Run 1 measurements of Higgs boson production and couplings in the decay channel H → ZZ∗ → ` +` −` 0+` 0−, where `, `0 = e or µ, 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 → ZZ∗ → 4` signal is observed with a significance of 8.1 standard deviations, with an expectation of 6.2 standard deviations, at mH = 125.36 GeV, the combined ATLAS measurement of the Higgs boson mass from the H → γγ and H → ZZ∗ → 4` channels. The production rate relative to the Standard Model expectation, the signal strength, is measured in four different production categories in the H → ZZ∗ → 4` channel. The measured signal strength, at this mass, and with all categories combined, is 1.44 +0.40 −0.33. The signal strength for Higgs boson production in gluon fusion or in association with tt¯ or b ¯b pairs is found to be 1.7 +0.5 −0.4 , while the signal strength for vector-boson fusion combined with W H/ZH associated production is found to be 0.3 +1.6 −0.9 .

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