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Scientific article
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English

Searches for lepton-flavour-violating decays of the Higgs boson into $e\tau$ and $\mu\tau$ in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector

ContributorsATLAS Collaboration
Published inThe journal of high energy physics, vol. 2023, 166
Publication date2023
First online date2023-07-21
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 $ \sqrt{s} $ = 13 TeV, corresponding to an integrated luminosity of 138 fb$^{−1}$. Leptonic (τ → ℓν$_{ℓ}$ν$_{τ}$) and hadronic (τ → hadrons ν$_{τ}$) 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, $ \mathcal{B} $(H → eτ) < 0.20% (0.12%) and $ \mathcal{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, $ \mathcal{B} $(H → μτ) → $ \mathcal{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.

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Keywords
  • Hadron-Hadron Scattering
  • P p: colliding beams
  • Higgs particle: leptonic decay
  • Higgs particle: rare decay
  • P p: scattering
  • Lepton: flavor: violation
  • Higgs particle: branching ratio
  • Branching ratio: upper limit
  • Background
  • ATLAS
  • Muon
  • Electron
  • Tau: particle identification
  • Tau: leptonic decay
  • Tau: hadronic decay
  • CERN LHC Coll
  • Statistical analysis
  • Data analysis method
  • Experimental results
  • Higgs particle --> electron tau
  • Higgs particle --> muon tau
  • 13000 GeV-cms
Citation (ISO format)
ATLAS Collaboration. Searches for lepton-flavour-violating decays of the Higgs boson into $e\tau$ and $\mu\tau$ in $\sqrt{s}=13$ TeV $pp$ collisions with the ATLAS detector. In: The journal of high energy physics, 2023, vol. 2023, p. 166. doi: 10.1007/jhep07(2023)166
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Article (Published version)
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ISSN of the journal1029-8479
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