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## Abstract / Description of output

A search for pair-produced vector-like quarks using events with exactly one lepton (e or μ), at least four jets including at least one b-tagged jet, and large missing transverse momentum is presented. Data from proton–proton col-

lisions at a centre-of-mass energy of √s =13 TeV, recorded by the ATLAS detector at the LHC from 2015 to 2018 and corresponding to an integrated luminosity of 139 fb−1, are analysed. Vector-like partners T and B of the top and bottom quarks are considered, as is a vector-like X with charge +5/3, assuming their decay into a W , Z , or Higgs boson and a third-generation quark. No significant deviations from the Standard Model expectation are observed. Upper limits on the production cross-section of T and B quark pairs as a

function of their mass are derived for various decay branching ratio scenarios. The strongest lower limits on the masses are 1.59 TeV assuming mass-degenerate vector-like quarks and branching ratios corresponding to the weak-isospin doublet model, and 1.47 TeV (1.46 TeV) for exclusive T → Z t (B/ X → W t) decays. In addition, lower limits on the T and B quark masses are derived for all possible branching ratios.

lisions at a centre-of-mass energy of √s =13 TeV, recorded by the ATLAS detector at the LHC from 2015 to 2018 and corresponding to an integrated luminosity of 139 fb−1, are analysed. Vector-like partners T and B of the top and bottom quarks are considered, as is a vector-like X with charge +5/3, assuming their decay into a W , Z , or Higgs boson and a third-generation quark. No significant deviations from the Standard Model expectation are observed. Upper limits on the production cross-section of T and B quark pairs as a

function of their mass are derived for various decay branching ratio scenarios. The strongest lower limits on the masses are 1.59 TeV assuming mass-degenerate vector-like quarks and branching ratios corresponding to the weak-isospin doublet model, and 1.47 TeV (1.46 TeV) for exclusive T → Z t (B/ X → W t) decays. In addition, lower limits on the T and B quark masses are derived for all possible branching ratios.

Original language | English |
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Article number | 719 |

Pages (from-to) | 1-31 |

Number of pages | 31 |

Journal | The European Physical Journal C |

Volume | 83 |

Issue number | 8 |

DOIs | |

Publication status | Published - 10 Aug 2023 |

## Keywords / Materials (for Non-textual outputs)

- Symmetry-Breaking
- Measuring Masses