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Search for flavour-changing neutral current interactions of the top quark and the Higgs boson in events with a pair of τ -leptons in pp collisions at √s = 13 TeV with the ATLAS detector ATLAS Collaboration

Abstract

A search for flavour-changing neutral current (FCNC) tqH interactions involving a top quark, another up-type quark (q = u, c), and a Standard Model (SM) Higgs boson decaying into a τ -lepton pair (H → τ +τ −) is presented. The search is based on a dataset of pp collisions at √ s = 13 TeV that corresponds to an integrated luminosity of 139 fb−1 recorded with the ATLAS detector at the Large Hadron Collider. Two processes are considered: single top quark FCNC production in association with a Higgs boson (pp → tH), and top quark pair production in which one of top quarks decays into W b and the other decays into qH through the FCNC interactions. The search selects events with two hadronically decaying τ -lepton candidates (τhad) or at least one τhad with an additional lepton (e, µ), as well as multiple jets. Event kinematics is used to separate signal from the background through a multivariate discriminant. A slight excess of data is observed with a significance of 2.3σ above the expected SM background, and 95% CL upper limits on the t → qH branching ratios are derived. The observed (expected) 95% CL upper limits set on the t → cH and t → uH branching ratios are 9.4 × 10−4 (4.8 +2.2 −1.4 × 10−4 ) and 6.9 × 10−4 (3.5 +1.5 −1.0 × 10−4 ), respectively. The corresponding combined observed (expected) upper limits on the dimension-6 operator Wilson coefficients in the effective tqH couplings are Ccφ < 1.35 (0.97) and Cuφ < 1.16 (0.82).

Item Metadata

Title
Search for flavour-changing neutral current interactions of the top quark and the Higgs boson in events with a pair of τ -leptons in pp collisions at √s = 13 TeV with the ATLAS detector
Creator
ATLAS Collaboration
Publisher
Springer Berlin Heidelberg
Date Issued
2023-06-23
Description
A search for flavour-changing neutral current (FCNC) tqH interactions involving a top quark, another up-type quark (q = u, c), and a Standard Model (SM) Higgs boson decaying into a τ -lepton pair (H → τ +τ −) is presented. The search is based on a dataset of pp collisions at √ s = 13 TeV that corresponds to an integrated luminosity of 139 fb−1 recorded with the ATLAS detector at the Large Hadron Collider. Two processes are considered: single top quark FCNC production in association with a Higgs boson (pp → tH), and top quark pair production in which one of top quarks decays into W b and the other decays into qH through the FCNC interactions. The search selects events with two hadronically decaying τ -lepton candidates (τhad) or at least one τhad with an additional lepton (e, µ), as well as multiple jets. Event kinematics is used to separate signal from the background through a multivariate discriminant. A slight excess of data is observed with a significance of 2.3σ above the expected SM background, and 95% CL upper limits on the t → qH branching ratios are derived. The observed (expected) 95% CL upper limits set on the t → cH and t → uH branching ratios are 9.4 × 10−4 (4.8 +2.2 −1.4 × 10−4 ) and 6.9 × 10−4 (3.5 +1.5 −1.0 × 10−4 ), respectively. The corresponding combined observed (expected) upper limits on the dimension-6 operator Wilson coefficients in the effective tqH couplings are Ccφ < 1.35 (0.97) and Cuφ < 1.16 (0.82).
Subject
Flavour Changing Neutral Currents; Hadron-Hadron Scattering; Higgs Physics; Top Physics
Genre
Article
Type
Text
Language
eng
Date Available
2023-09-15
Provider
Vancouver : University of British Columbia Library
Rights
Attribution 4.0 International (CC BY 4.0)
DOI
10.14288/1.0435886
URI
http://hdl.handle.net/2429/85941
Affiliation
Science, Faculty of; TRIUMF; Non UBC; Physics and Astronomy, Department of
Citation
Journal of High Energy Physics. 2023 Jun 23;2023(6):155
Publisher DOI
10.1007/JHEP06(2023)155
Peer Review Status
Reviewed
Scholarly Level
Faculty; Researcher
Copyright Holder
The Author(s)
Rights URI
http://creativecommons.org/licenses/by/4.0/
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Attribution 4.0 International (CC BY 4.0)