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Scientific article
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English

Search for a new scalar resonance in flavour-changing neutral-current top-quark decays t \rightarrow qX (q=u,c), with X \rightarrow b\bar{b}, in proton-proton collisions at \sqrt{s}=13 TeV with the ATLAS detector

ContributorsATLAS Collaboration
Published inThe journal of high energy physics, vol. 2023, 199
Publication date2023
First online date2023-07-26
Abstract

A search for flavour-changing neutral-current decays of a top quark into an up-type quark (either up or charm) and a light scalar particle X decaying into a bottom anti-bottom quark pair is presented. The search focuses on top-quark pair production where one top quark decays to qX, with X → $ b\overline{b} $, and the other top quark decays according to the Standard Model, with the W boson decaying leptonically. The final state is thus characterised by an isolated electron or muon and at least four jets. Events are categorised according to the multiplicity of jets and jets tagged as originating from b-quarks, and a neural network is used to discriminate between signal and background processes. The data analysed correspond to 139 fb$^{−1}$ of proton–proton collisions at a centre-of-mass energy of 13 TeV, recorded with the ATLAS detector at the LHC. The 95% confidence-level upper limits between 0.019% and 0.062% are derived for the branching fraction $ \mathcal{B} $(t → uX) and between 0.018% and 0.078% for the branching fraction $ \mathcal{B} $(t → cX), for masses of the scalar particle X between 20 and 160 GeV.

eng
Keywords
  • Hadron-Hadron Scattering
  • P p: colliding beams
  • Resonance: production
  • Top: rare decay
  • Neutral current: flavor changing
  • P p: scattering
  • Top: pair production
  • Bottom: pair production
  • W: leptonic decay
  • Jet: multiplicity
  • Scalar particle: mass
  • Resonance: scalar
  • Top: branching ratio: upper limit
  • ATLAS
  • Final state: ((n)jet lepton)
  • Jet: bottom
  • Bottom: particle identification
  • Muon
  • Electron
  • CERN LHC Coll
  • Charm
  • Up
  • Background
  • Bottom anti-bottom
  • Neural network
  • Data analysis method
  • Experimental results
  • 13000 GeV-cms
Citation (ISO format)
ATLAS Collaboration. Search for a new scalar resonance in flavour-changing neutral-current top-quark decays <i>t \rightarrow qX (q=u,c), </i>with <i>X \rightarrow b\bar{b}, </i>in proton-proton collisions at <i>\sqrt{s}=13 </i>TeV with the ATLAS detector. In: The journal of high energy physics, 2023, vol. 2023, p. 199. doi: 10.1007/jhep07(2023)199
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ISSN of the journal1029-8479
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