This Letter reports on a search for off-shell production of the Higgs boson using 139 fb−1 of pp collision data at s= 13 TeV collected by the ATLAS detector at the Large Hadron Collider. The signature is a pair of Z bosons, with contributions from both the production and subsequent decay of a virtual Higgs boson and the interference of that process with other processes. The two observable final states are ZZ→4ℓ and ZZ→2ℓ2ν with ℓ=e or μ. In the ZZ→4ℓ final state, a dense Neural Network is used to enhance analysis sensitivity with respect to matrix element-based discrimination. The background-only hypothesis is rejected with an observed (expected) significance of 3.3 (2.2) standard deviations, representing experimental evidence for off-shell Higgs boson production. Assuming that no new particles enter the production of the virtual Higgs boson, its total width can be deduced from the measurement of its off-shell production cross-section. The measured total width of the Higgs boson is 4.5−2.5+3.3 MeV, and the observed (expected) upper limit on the total width is found to be 10.5 (10.9) MeV at 95% confidence level.

Evidence of off-shell Higgs boson production from ZZ leptonic decay channels and constraints on its total width with the ATLAS detector / Betti, Alessandra; DE SALVO, Alessandro; Di Domenico, Antonio.; Dionisi, Carlo.; Bini, Cesare; Luci, Claudio; POMPA PACCHI, Elena; Morodei, Federico; Lacava, Francesco; SAFAI TEHRANI, Francesco; Artoni, Giacomo; Santi, Lorenzo; Padovano, Giovanni; Martinelli, Luca; Maiani, Luciano; Bauce, Matteo; Gauzzi, Paolo; Gentile, Simonetta; Giagu, Stefano; Ippolito, Valerio; Padovano, Giovanni. - In: PHYSICS LETTERS. SECTION B. - ISSN 0370-2693. - 846:(2023), pp. 1-29. [10.1016/j.physletb.2023.138223]

Evidence of off-shell Higgs boson production from ZZ leptonic decay channels and constraints on its total width with the ATLAS detector

Betti Alessandra;De Salvo Alessandro;Di Domenico Antonio.;Dionisi Carlo.;Bini Cesare;Luci Claudio;Pompa Pacchi Elena;Morodei Federico;Lacava Francesco;Safai Tehrani Francesco;Artoni Giacomo;Santi Lorenzo;Padovano Giovanni;Martinelli Luca;Maiani Luciano;Bauce Matteo;Gauzzi Paolo;Gentile Simonetta;Giagu Stefano;Ippolito Valerio;Padovano Giovanni
2023

Abstract

This Letter reports on a search for off-shell production of the Higgs boson using 139 fb−1 of pp collision data at s= 13 TeV collected by the ATLAS detector at the Large Hadron Collider. The signature is a pair of Z bosons, with contributions from both the production and subsequent decay of a virtual Higgs boson and the interference of that process with other processes. The two observable final states are ZZ→4ℓ and ZZ→2ℓ2ν with ℓ=e or μ. In the ZZ→4ℓ final state, a dense Neural Network is used to enhance analysis sensitivity with respect to matrix element-based discrimination. The background-only hypothesis is rejected with an observed (expected) significance of 3.3 (2.2) standard deviations, representing experimental evidence for off-shell Higgs boson production. Assuming that no new particles enter the production of the virtual Higgs boson, its total width can be deduced from the measurement of its off-shell production cross-section. The measured total width of the Higgs boson is 4.5−2.5+3.3 MeV, and the observed (expected) upper limit on the total width is found to be 10.5 (10.9) MeV at 95% confidence level.
2023
HEP; Z boson; Higgs boson width; standard model
01 Pubblicazione su rivista::01a Articolo in rivista
Evidence of off-shell Higgs boson production from ZZ leptonic decay channels and constraints on its total width with the ATLAS detector / Betti, Alessandra; DE SALVO, Alessandro; Di Domenico, Antonio.; Dionisi, Carlo.; Bini, Cesare; Luci, Claudio; POMPA PACCHI, Elena; Morodei, Federico; Lacava, Francesco; SAFAI TEHRANI, Francesco; Artoni, Giacomo; Santi, Lorenzo; Padovano, Giovanni; Martinelli, Luca; Maiani, Luciano; Bauce, Matteo; Gauzzi, Paolo; Gentile, Simonetta; Giagu, Stefano; Ippolito, Valerio; Padovano, Giovanni. - In: PHYSICS LETTERS. SECTION B. - ISSN 0370-2693. - 846:(2023), pp. 1-29. [10.1016/j.physletb.2023.138223]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1694192
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