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Measurement of off-shell Higgs boson production in the H∗ → ZZ → 4ℓ decay channel using a neural simulation-based inference technique in 13 TeV pp collisions with the ATLAS detector

Aad, G. ; Åkesson, T.P.A. LU orcid ; Astrand, K.S.V. LU ; Doglioni, C. LU ; Ekman, P.A. LU orcid ; Hedberg, V. LU ; Herde, H. LU orcid ; Konya, B. LU ; Lytken, E. LU orcid and Poettgen, R. LU orcid , et al. (2025) In Reports on Progress in Physics 88(5).
Abstract
A measurement of off-shell Higgs boson production in the H∗ → ZZ → 4ℓ decay channel is presented. The measurement uses 140 fb−1 of proton–proton collisions at √s = 13 TeV collected by the ATLAS detector at the Large Hadron Collider and supersedes the previous result in this decay channel using the same dataset. The data analysis is performed using a neural simulation-based inference method, which builds per-event likelihood ratios using neural networks. The observed (expected) off-shell Higgs boson production signal strength in the ZZ → 4ℓ decay channel at 68% CL is 0.87+0.75−0.54 (1.00+1.04−0.95). The evidence for off-shell Higgs boson production using the ZZ → 4ℓ decay channel has an observed (expected) significance of 2.5σ (1.3σ). The... (More)
A measurement of off-shell Higgs boson production in the H∗ → ZZ → 4ℓ decay channel is presented. The measurement uses 140 fb−1 of proton–proton collisions at √s = 13 TeV collected by the ATLAS detector at the Large Hadron Collider and supersedes the previous result in this decay channel using the same dataset. The data analysis is performed using a neural simulation-based inference method, which builds per-event likelihood ratios using neural networks. The observed (expected) off-shell Higgs boson production signal strength in the ZZ → 4ℓ decay channel at 68% CL is 0.87+0.75−0.54 (1.00+1.04−0.95). The evidence for off-shell Higgs boson production using the ZZ → 4ℓ decay channel has an observed (expected) significance of 2.5σ (1.3σ). The expected result represents a significant improvement relative to that of the previous analysis of the same dataset, which obtained an expected significance of 0.5σ. When combined with the most recent ATLAS measurement in the ZZ → 2ℓ2ν decay channel, the evidence for off-shell Higgs boson production has an observed (expected) significance of 3.7σ (2.4σ). The off-shell measurements are combined with the measurement of on-shell Higgs boson production to obtain constraints on the Higgs boson total width. The observed (expected) value of the Higgs boson width at 68% CL is 4.3+2.7−1.9 (4.1+3.5−3.4) MeV. © 2025 The Author(s). (Less)
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organization
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type
Contribution to journal
publication status
published
subject
keywords
frequentist statistics, likelihood-free inference, machine learning, neural simulation-based inference, parameter inference
in
Reports on Progress in Physics
volume
88
issue
5
article number
057803
publisher
IOP Publishing
external identifiers
  • scopus:105007211941
  • pmid:40239680
ISSN
0034-4885
DOI
10.1088/1361-6633/adcd9a
language
English
LU publication?
yes
id
cb9fe45a-3bd3-4b2e-b60b-582c59f8a0d6
date added to LUP
2026-03-10 15:02:41
date last changed
2026-03-11 03:45:39
@article{cb9fe45a-3bd3-4b2e-b60b-582c59f8a0d6,
  abstract     = {{A measurement of off-shell Higgs boson production in the H∗ → ZZ → 4ℓ decay channel is presented. The measurement uses 140 fb−1 of proton–proton collisions at √s = 13 TeV collected by the ATLAS detector at the Large Hadron Collider and supersedes the previous result in this decay channel using the same dataset. The data analysis is performed using a neural simulation-based inference method, which builds per-event likelihood ratios using neural networks. The observed (expected) off-shell Higgs boson production signal strength in the ZZ → 4ℓ decay channel at 68% CL is 0.87+0.75−0.54 (1.00+1.04−0.95). The evidence for off-shell Higgs boson production using the ZZ → 4ℓ decay channel has an observed (expected) significance of 2.5σ (1.3σ). The expected result represents a significant improvement relative to that of the previous analysis of the same dataset, which obtained an expected significance of 0.5σ. When combined with the most recent ATLAS measurement in the ZZ → 2ℓ2ν decay channel, the evidence for off-shell Higgs boson production has an observed (expected) significance of 3.7σ (2.4σ). The off-shell measurements are combined with the measurement of on-shell Higgs boson production to obtain constraints on the Higgs boson total width. The observed (expected) value of the Higgs boson width at 68% CL is 4.3+2.7−1.9 (4.1+3.5−3.4) MeV. © 2025 The Author(s).}},
  author       = {{Aad, G. and Åkesson, T.P.A. and Astrand, K.S.V. and Doglioni, C. and Ekman, P.A. and Hedberg, V. and Herde, H. and Konya, B. and Lytken, E. and Poettgen, R. and Smirnova, O. and Wallin, E.J. and Zwalinski, L.}},
  issn         = {{0034-4885}},
  keywords     = {{frequentist statistics; likelihood-free inference; machine learning; neural simulation-based inference; parameter inference}},
  language     = {{eng}},
  number       = {{5}},
  publisher    = {{IOP Publishing}},
  series       = {{Reports on Progress in Physics}},
  title        = {{Measurement of off-shell Higgs boson production in the H∗ → ZZ → 4ℓ decay channel using a neural simulation-based inference technique in 13 TeV pp collisions with the ATLAS detector}},
  url          = {{http://dx.doi.org/10.1088/1361-6633/adcd9a}},
  doi          = {{10.1088/1361-6633/adcd9a}},
  volume       = {{88}},
  year         = {{2025}},
}