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Constraints on the off-shell Higgs boson signal strength in the high-mass ZZ and WW final states with the ATLAS detector

CollaborationWith : Ancu, Lucian Stefan / Barone, Gaetano / Bell, William / Benhar Noccioli, Eleonora / Bilbao De Mendizabal, Javier / Camacho Toro, Reina / Clark, Allan Geoffrey / Delitzsch, Chris Malena / Della Volpe, Domenico / Doglioni, Caterina / Ferrere, Didier / Gadomski, Szymon / Golling, Tobias / Gonzalez Sevilla, Sergio / Gramling, Johanna Léna / Guescini, Francesco / Iacobucci, Giuseppe / Katre, Akshay / La Rosa, Alessandro / Mermod, Philippe / Miucci, Antonio / Muenstermann, Daniel / Picazio, Attilio / Ristic, Branislav / Tykhonov, Andrii / Vallecorsa, Sofia / Wu, Xin
Published in The European Physical Journal. C, Particles and Fields. 2015, vol. 75, no. 7, 335
Collection Open Access - SCOAP3
Abstract Measurements of the ZZ and WW final states in the mass range above the 2mZ and 2mW thresholds provide a unique opportunity to measure the off-shell coupling strength of the Higgs boson. This paper presents constraints on the off-shell Higgs boson event yields normalised to the Standard Model prediction (signal strength) in the ZZ→4ℓ , ZZ→2ℓ2ν and WW→eνμν final states. The result is based on pp collision data collected by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 20.3 fb -1 at a collision energy of s=8 TeV. Using the CLs method, the observed 95 % confidence level (CL) upper limit on the off-shell signal strength is in the range 5.1–8.6, with an expected range of 6.7–11.0. In each case the range is determined by varying the unknown gg→ZZ and gg→WW background K-factor from higher-order quantum chromodynamics corrections between half and twice the value of the known signal K-factor. Assuming the relevant Higgs boson couplings are independent of the energy scale of the Higgs boson production, a combination with the on-shell measurements yields an observed (expected) 95 % CL upper limit on ΓH/ΓHSM in the range 4.5–7.5 (6.5–11.2) using the same variations of the background K-factor. Assuming that the unknown gg→VV background K-factor is equal to the signal K-factor, this translates into an observed (expected) 95 % CL upper limit on the Higgs boson total width of 22.7 (33.0) MeV.
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ATLAS COLLABORATION. Constraints on the off-shell Higgs boson signal strength in the high-mass ZZ and WW final states with the ATLAS detector. In: The European Physical Journal. C, Particles and Fields, 2015, vol. 75, n° 7, p. 335. doi: 10.1140/epjc/s10052-015-3542-2 https://archive-ouverte.unige.ch/unige:74434

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Deposited on : 2015-07-31

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