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



Aad, G, Abbott, B, Abeling, K, Abicht, NJ, Abidi, SH, Aboulhorma, A, Abramowicz, H, Abreu, H, Abulaiti, Y, Abusleme Hoffman, AC
et al (show 2922 more authors) (2023) Searches for lepton-flavour-violating decays of the Higgs boson into eτ and μτ in √s=13 TeV pp collisions with the ATLAS detector. JOURNAL OF HIGH ENERGY PHYSICS, 2023 (7). 166-.

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Abstract

<jats:title>A<jats:sc>bstract</jats:sc> </jats:title><jats:p>This paper presents direct searches for lepton flavour violation in Higgs boson decays, <jats:italic>H</jats:italic> → <jats:italic>eτ</jats:italic> and <jats:italic>H</jats:italic> → <jats:italic>μτ</jats:italic>, 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 <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \sqrt{s} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math></jats:alternatives></jats:inline-formula> = 13 TeV, corresponding to an integrated luminosity of 138 fb<jats:sup><jats:italic>−</jats:italic>1</jats:sup>. Leptonic (<jats:italic>τ</jats:italic> → <jats:italic>ℓν</jats:italic><jats:sub><jats:italic>ℓ</jats:italic></jats:sub><jats:italic>ν</jats:italic><jats:sub><jats:italic>τ</jats:italic></jats:sub>) and hadronic (<jats:italic>τ</jats:italic> → hadrons <jats:italic>ν</jats:italic><jats:sub><jats:italic>τ</jats:italic></jats:sub>) decays of the <jats:italic>τ</jats:italic>-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, <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \mathcal{B} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>B</mml:mi> </mml:math></jats:alternatives></jats:inline-formula>(<jats:italic>H</jats:italic> → <jats:italic>eτ</jats:italic>) <jats:italic>&lt;</jats:italic> 0<jats:italic>.</jats:italic>20% (0<jats:italic>.</jats:italic>12%) and <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \mathcal{B} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>B</mml:mi> </mml:math></jats:alternatives></jats:inline-formula>(<jats:italic>H</jats:italic> → <jats:italic>μτ</jats:italic> ) <jats:italic>&lt;</jats:italic> 0<jats:italic>.</jats:italic>18% (0<jats:italic>.</jats:italic>09%), are obtained with the MC-template method from a simultaneous measurement of potential <jats:italic>H</jats:italic> → <jats:italic>eτ</jats:italic> and <jats:italic>H</jats:italic> → <jats:italic>μτ</jats:italic> signals. The best-fit branching ratio difference, <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \mathcal{B} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>B</mml:mi> </mml:math></jats:alternatives></jats:inline-formula>(<jats:italic>H</jats:italic> → <jats:italic>μτ</jats:italic>) → <jats:inline-formula><jats:alternatives><jats:tex-math>$$ \mathcal{B} $$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>B</mml:mi> </mml:math></jats:alternatives></jats:inline-formula>(<jats:italic>H</jats:italic> → <jats:italic>eτ</jats:italic>), measured with the Symmetry method in the channel where the <jats:italic>τ</jats:italic>-lepton decays to leptons, is (0<jats:italic>.</jats:italic>25 ± 0<jats:italic>.</jats:italic>10)%, compatible with a value of zero within 2<jats:italic>.</jats:italic>5<jats:italic>σ</jats:italic>.</jats:p>

Item Type: Article
Uncontrolled Keywords: Hadron-Hadron Scattering
Divisions: Faculty of Science and Engineering > School of Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 09 Aug 2023 10:25
Last Modified: 18 Mar 2024 04:09
DOI: 10.1007/JHEP07(2023)166
Open Access URL: https://link.springer.com/article/10.1007/JHEP07(2...
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3172096