PT Journal
AU ATLAS Collaboration (Aaboud, Mea
   Alvarez Piqueras, D
   Aparisi Pozo, JA
   Bailey, AJ
   Barranco Navarro, L
   Cabrera Urban, S
   Castillo, FL
   Castillo Gimenez, V
   Cerda Alberich, L
   Costa, MJ
   Escobar, C
   Estrada Pastor, O
   Ferrer, A
   Fiorini, L
   Fullana Torregrosa, E
   Fuster, J
   Garcia, C
   Garcia Navarro, JE
   Gonzalez de la Hoz, S
   Higon-Rodriguez, E
   Jimenez Pena, J
   Lacasta, C
   Lozano Bahilo, JJ
   Madaffari, D
   Mamuzic, J
   Marti-Garcia, S
   Melini, D
   Miñano, M
   Mitsou, VA
   Rodriguez Bosca, S
   Rodriguez Rodriguez, D
   Ruiz-Martinez, A
   Salt, J
   Santra, A
   Soldevila, U
   Sanchez, J
   Valero, A
   Valls Ferrer, JA
   Vos, M
TI Search for top-quark decays t -> Hq with 36 fb(-1) of pp collision data at root s=13 TeV with the ATLAS detector
SO Journal of High Energy Physics
JI J. High Energy Phys.
PY 2019
BP 123
EP 67pp
VL 05
IS 5
DI 10.1007/JHEP05(2019)123
LA English
DE Hadron-Hadron scattering (experiments); Rare decay; Top physics
AB 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 = 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 Hbb and H (+-) decay modes, respectively. The high multiplicity of b-quark jets, or the presence of hadronically decaying -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 x 10(-3) (8.3 x 10(-4)) and 1.2 x 10(-3) (8.3 x 10(-4)), respectively. The corresponding combined observed (expected) upper limits on the |(tcH)| and |(tuH)| couplings are 0.064 (0.055) and 0.066 (0.055), respectively.
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