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.]
| Original language | English |
|---|---|
| Article number | 123 |
| Journal | Journal of High Energy Physics |
| Volume | 2019 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - 2019 May 1 |
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Keywords
- Hadron-Hadron scattering (experiments)
- Rare decay
- Top physics
ASJC Scopus subject areas
- Nuclear and High Energy Physics
Cite this
Search for top-quark decays t → Hq with 36 fb−1 of pp collision data at √s = 13 TeV with the ATLAS detector. / The ATLAS Collaboration.
In: Journal of High Energy Physics, Vol. 2019, No. 5, 123, 01.05.2019.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Search for top-quark decays t → Hq with 36 fb−1 of pp collision data at √s = 13 TeV with the ATLAS detector
AU - The ATLAS Collaboration
AU - Aaboud, M.
AU - Aad, G.
AU - Abbott, B.
AU - Abbott, D. C.
AU - Abdinov, O.
AU - Abeloos, B.
AU - Abhayasinghe, D. K.
AU - Abidi, S. H.
AU - AbouZeid, O. S.
AU - Abraham, N. L.
AU - Abramowicz, H.
AU - Abreu, H.
AU - Abulaiti, Y.
AU - Acharya, B. S.
AU - Adachi, S.
AU - Adam, L.
AU - Adamczyk, L.
AU - Adamek, L.
AU - Adelman, J.
AU - Adersberger, M.
AU - Adiguzel, A.
AU - Adye, T.
AU - Affolder, A. A.
AU - Afik, Y.
AU - Agheorghiesei, C.
AU - Aguilar-Saavedra, J. A.
AU - Ahmadov, F.
AU - Aielli, G.
AU - Akatsuka, S.
AU - Åkesson, T. P.A.
AU - Akilli, E.
AU - Akimov, A. V.
AU - Alberghi, G. L.
AU - Albert, J.
AU - Albicocco, P.
AU - Alconada Verzini, M. J.
AU - Alderweireldt, S.
AU - Aleksa, M.
AU - Aleksandrov, I. N.
AU - Alexa, C.
AU - Alexandre, D.
AU - Alexopoulos, T.
AU - Alhroob, M.
AU - Ali, B.
AU - Alimonti, G.
AU - Alison, J.
AU - Alkire, S. P.
AU - Allaire, C.
AU - Mitani, Takashi
AU - Morinaga, Masahiro
PY - 2019/5/1
Y1 - 2019/5/1
N2 - 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.]
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 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.]
KW - Hadron-Hadron scattering (experiments)
KW - Rare decay
KW - Top physics
UR - http://www.scopus.com/inward/record.url?scp=85066135451&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85066135451&partnerID=8YFLogxK
U2 - 10.1007/JHEP05(2019)123
DO - 10.1007/JHEP05(2019)123
M3 - Article
AN - SCOPUS:85066135451
VL - 2019
JO - Journal of High Energy Physics
JF - Journal of High Energy Physics
SN - 1126-6708
IS - 5
M1 - 123
ER -