Searches for lepton-flavour-violating decays of the Higgs boson into eτ and μτ in √s = 13 TeV pp collisions with the ATLAS detector

The ATLAS collaboration

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Abstract

This paper presents direct searches for lepton flavour violation in Higgs boson decays, H → eτ and H → μτ, performed using data collected with the ATLAS detector at the LHC. The searches are based on a data sample of proton-proton collisions at a centre-of-mass energy s = 13 TeV, corresponding to an integrated luminosity of 138 fb −1. Leptonic (τ → ℓν ντ) and hadronic (τ → hadrons ντ) decays of the τ-lepton are considered. Two background estimation techniques are employed: the MC-template method, based on data-corrected simulation samples, and the Symmetry method, based on exploiting the symmetry between electrons and muons in the Standard Model backgrounds. No significant excess of events is observed and the results are interpreted as upper limits on lepton-flavour-violating branching ratios of the Higgs boson. The observed (expected) upper limits set on the branching ratios at 95% confidence level, B (H → eτ) < 0.20% (0.12%) and B (H → μτ) < 0.18% (0.09%), are obtained with the MC-template method from a simultaneous measurement of potential H → eτ and H → μτ signals. The best-fit branching ratio difference, B (H → μτ) → B (H → eτ), measured with the Symmetry method in the channel where the τ-lepton decays to leptons, is (0.25 ± 0.10)%, compatible with a value of zero within 2.5σ. [Figure not available: see fulltext.].

Original languageEnglish
Article number166
JournalJournal of High Energy Physics
Volume2023
Issue number7
DOIs
StatePublished - Jul 2023

Funding

FundersFunder number
CEA-DRF
Cantons of Bern and Geneva
DNSRCIN2P3-CNRS
EU-ESF
GenT Programmes Generalitat Valenciana, Spain
La Caixa Banking Foundation
MIZŠ
MNE
Norwegian Financial Mechanism2014-2021
PROMETEO
RGC
UNCESCI/013
Wallenberg Foundation
National Science Foundation
U.S. Department of Energy
Alexander von Humboldt-Stiftung
CRC Health Group21/SCI/017
CRC Health Group
Canarie
H2020 Marie Skłodowska-Curie Actions
Multiple Sclerosis Scientific Research Foundation
CERN
Compute Canada
Göran Gustafssons Stiftelser
Natural Sciences and Engineering Research Council of Canada
National Research Council Canada
Canada Foundation for Innovation
Science and Technology Facilities Council
Leverhulme Trust
European Research Council
European Cooperation in Science and Technology
Australian Research Council
National Stroke Foundation
Neurosurgical Research Foundation
Helmholtz-Gemeinschaft
Minerva Foundation
Deutsche Forschungsgemeinschaft
Agence Nationale de la Recherche
Japan Society for the Promotion of Science
Ministry of Education, Culture, Sports, Science and Technology
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
Danmarks Grundforskningsfond
Fundação de Amparo à Pesquisa do Estado de São Paulo
National Natural Science Foundation of China
Ministerstvo Školství, Mládeže a Tělovýchovy
Fundação para a Ciência e a Tecnologia
Bundesministerium für Bildung und Forschung
Chinese Academy of Sciences
Austrian Science Fund
Generalitat de Catalunya
Ministry of Science and Technology of the People's Republic of China
Agencia Nacional de Promoción Científica y Tecnológica
Nederlandse Organisatie voor Wetenschappelijk Onderzoek
Bundesministerium für Wissenschaft, Forschung und Wirtschaft
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Nella and Leon Benoziyo Center for Neurological Diseases, Weizmann Institute of Science
Israel Science Foundation
Instituto Nazionale di Fisica Nucleare
Narodowe Centrum Nauki
Javna Agencija za Raziskovalno Dejavnost RS
Ministarstvo Prosvete, Nauke i Tehnološkog Razvoja
Ministerio de Ciencia e Innovación
Centre National pour la Recherche Scientifique et Technique
Staatssekretariat für Bildung, Forschung und Innovation
Horizon 2020
British Columbia Knowledge Development Fund
European Regional Development Fund
Defence Science Institute
Narodowa Agencja Wymiany Akademickiej
Institutul de Fizică Atomică
Agencia Nacional de Investigación y Desarrollo
Royal Society of South Australia
Irish Rugby Football Union

    Keywords

    • Hadron-Hadron Scattering

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