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Search for top-quark decays t → Hq with 36 fb−1 of pp collision data at √s = 13 TeV with the ATLAS detector

, ; Aaboud, M; Åkesson, Torsten LU ; Bocchetta, Simona LU ; Bryngemark, Lene LU ; Corrigan, Eric LU ; Doglioni, Caterina LU ; Gregersen, Kristian LU ; Brottmann Hansen, Eva LU and Hedberg, Vincent LU , et al. (2019) In Journal of High Energy Physics 2019(5).
Abstract
A search for flavour-changing neutral current decays of a top quark into an up-type quark (q = u, c) and the Standard Model Higgs boson, t → Hq, is presented. The search is based on a dataset of pp collisions at s = 13 TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider and corresponding to an integrated luminosity of 36.1 fb−1. Two complementary analyses are performed to search for top-quark pair events in which one top quark decays into Wb and the other top quark decays into Hq, and target the H→ bb¯ and H → τ+τ− decay modes, respectively. The high multiplicity of b-quark jets, or the presence of hadronically decaying τ-leptons, is exploited in the two analyses respectively. Multivariate techniques are... (More)
A search for flavour-changing neutral current decays of a top quark into an up-type quark (q = u, c) and the Standard Model Higgs boson, t → Hq, is presented. The search is based on a dataset of pp collisions at s = 13 TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider and corresponding to an integrated luminosity of 36.1 fb−1. Two complementary analyses are performed to search for top-quark pair events in which one top quark decays into Wb and the other top quark decays into Hq, and target the H→ bb¯ and H → τ+τ− decay modes, respectively. The high multiplicity of b-quark jets, or the presence of hadronically decaying τ-leptons, is exploited in the two analyses respectively. Multivariate techniques are used to separate the signal from the background, which is dominated by top-quark pair production. No significant excess of events above the background expectation is found, and 95% CL upper limits on the t → Hq branching ratios are derived. The combination of these searches with ATLAS searches in diphoton and multilepton final states yields observed (expected) 95% CL upper limits on the t → Hc and t → Hu branching ratios of 1.1 × 10−3 (8.3 × 10−4) and 1.2 × 10−3 (8.3 × 10−4), respectively. The corresponding combined observed (expected) upper limits on the |λtcH| and |λtuH| couplings are 0.064 (0.055) and 0.066 (0.055), respectively.[Figure not available: see fulltext.] © 2019, The Author(s). (Less)
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Contribution to journal
publication status
published
subject
keywords
Hadron-Hadron scattering (experiments), Rare decay, Top physics
in
Journal of High Energy Physics
volume
2019
issue
5
publisher
Springer Verlag
external identifiers
  • scopus:85066135451
ISSN
1126-6708
DOI
10.1007/JHEP05(2019)123
language
English
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yes
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8300f83b-fb49-4af1-b57d-452cb60efd1e
date added to LUP
2019-06-13 08:07:33
date last changed
2019-07-02 04:48:00
@article{8300f83b-fb49-4af1-b57d-452cb60efd1e,
  abstract     = {A search for flavour-changing neutral current decays of a top quark into an up-type quark (q = u, c) and the Standard Model Higgs boson, t → Hq, is presented. The search is based on a dataset of pp collisions at s = 13 TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider and corresponding to an integrated luminosity of 36.1 fb−1. Two complementary analyses are performed to search for top-quark pair events in which one top quark decays into Wb and the other top quark decays into Hq, and target the H→ bb¯ and H → τ+τ− decay modes, respectively. The high multiplicity of b-quark jets, or the presence of hadronically decaying τ-leptons, is exploited in the two analyses respectively. Multivariate techniques are used to separate the signal from the background, which is dominated by top-quark pair production. No significant excess of events above the background expectation is found, and 95% CL upper limits on the t → Hq branching ratios are derived. The combination of these searches with ATLAS searches in diphoton and multilepton final states yields observed (expected) 95% CL upper limits on the t → Hc and t → Hu branching ratios of 1.1 × 10−3 (8.3 × 10−4) and 1.2 × 10−3 (8.3 × 10−4), respectively. The corresponding combined observed (expected) upper limits on the |λtcH| and |λtuH| couplings are 0.064 (0.055) and 0.066 (0.055), respectively.[Figure not available: see fulltext.] © 2019, The Author(s).},
  articleno    = {123},
  author       = {,  and Aaboud, M and Åkesson, Torsten and Bocchetta, Simona and Bryngemark, Lene and Corrigan, Eric and Doglioni, Caterina and Gregersen, Kristian and Brottmann Hansen, Eva and Hedberg, Vincent and Jarlskog, Göran and Kalderon, Charles and Kellermann, Edgar and Konya, Balazs and Lytken, Else and Mankinen, Katja and Marcon, Caterina and Mjörnmark, Ulf and Mullier, Geoffrey and Pöttgen, Ruth and Poulsen, Trine and Smirnova, Oxana and Zwalinski, L},
  issn         = {1126-6708},
  keyword      = {Hadron-Hadron scattering (experiments),Rare decay,Top physics},
  language     = {eng},
  number       = {5},
  publisher    = {Springer Verlag},
  series       = {Journal of High Energy Physics},
  title        = {Search for top-quark decays t → Hq with 36 fb−1 of pp collision data at √s = 13 TeV with the ATLAS detector},
  url          = {http://dx.doi.org/10.1007/JHEP05(2019)123},
  volume       = {2019},
  year         = {2019},
}