Scientific article
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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 \sqrt{s} = 13 TeV with the ATLAS detector

ContributorsATLAS Collaboration
Published inThe journal of high energy physics, vol. 2023, 155
Publication date2023
First online date2023-06-23

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 $ \sqrt{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 Wb and the other decays into qH through the FCNC interactions. The search selects events with two hadronically decaying τ-lepton candidates (τ$_{had}$) or at least one τ$_{had}$ 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\times {10}^{-4}\left({4.8}_{-1.4}^{+2.2}\times {10}^{-4}\right) $ and $ 6.9\times {10}^{-4}\left({3.5}_{-1.0}^{+1.5}\times {10}^{-4}\right) $, respectively. The corresponding combined observed (expected) upper limits on the dimension-6 operator Wilson coefficients in the effective tqH couplings are C$_{cϕ}$< 1.35 (0.97) and C$_{uϕ}$< 1.16 (0.82).

  • Flavour Changing Neutral Currents
  • Hadron-Hadron Scattering
  • Higgs Physics
  • Top Physics
  • P p: colliding beams
  • Neutral current: flavor changing
  • P p: scattering
  • Operator: Wilson
  • Top: pair production
  • Top: single production
  • Higgs particle: associated production
  • Top: rare decay
  • Higgs particle: leptonic decay
  • Tau: pair production
  • Tau: hadronic decay
  • Final state: ((n)jet)
  • Final state: ((n)jet lepton)
  • Top: branching ratio
  • Branching ratio: upper limit
  • Operator: higher-dimensional
  • Dimension: 6
  • Background
  • CERN LHC Coll
  • Kinematics
  • Experimental results
  • 13000 GeV-cms
Citation (ISO format)
ATLAS Collaboration. Search for flavour-changing neutral current interactions of the top quark and the Higgs boson in events with a pair of <i>τ</i>-leptons in <i>pp </i>collisions at <i> \sqrt{s} </i> = 13 TeV with the ATLAS detector. In: The journal of high energy physics, 2023, vol. 2023, p. 155. doi: 10.1007/jhep06(2023)155
Main files (1)
Article (Published version)
ISSN of the journal1029-8479

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