Search for top-quark decays t -> Hq with 36 fb(-1) of pp collision data at root s=13 TeV with the ATLAS detector

M. Aaboud; G. Aad; B. Abbott; O. Abdinov; B Abeloos; DK Abhayasinghe; S.H. Abidi; Ossama Sherif Alexander AbouZeid; NL Abraham; H. Abramowicz; H. Abreu; Y. Abulaiti; B.S. Acharya; Sosuke Adachi; L. Adamczyk; J. Adelman; M. Adersberger; A. Adiguzel; T. Adye; A. A. Affolder; Y.  Afik; C. Agheorghiesei; J. A. Aguilar-Saavedra; F. Ahmadov; G. Aielli; S. Akatsuka; T. P. A. Akesson; E. Akilli; Flavia de Almeida Dias; Geert-Jan Besjes; Milena Bajic; Mogens Dam; Gorm Aske Gram Krohn Galster; Alejandro Alonso Diaz; Jørgen Beck Hansen; Peter Henrik Hansen; Jørn Dines Hansen; James William Monk; hqz214 hqz214; Simon Holm Stark; Troels Christian Petersen; Graig Wiglesworth; Stefania Xella; ATLAS

doi:10.1007/JHEP05(2019)123

Search for top-quark decays t -> Hq with 36 fb(-1) of pp collision data at root s=13 TeV with the ATLAS detector

M. Aaboud, G. Aad, B. Abbott, O. Abdinov, B Abeloos, DK Abhayasinghe, S.H. Abidi, Ossama Sherif Alexander AbouZeid, NL Abraham, H. Abramowicz, H. Abreu, Y. Abulaiti, B.S. Acharya, Sosuke Adachi, L. Adamczyk, J. Adelman, M. Adersberger, A. Adiguzel, T. Adye, A. A. AffolderY. Afik, C. Agheorghiesei, J. A. Aguilar-Saavedra, F. Ahmadov, G. Aielli, S. Akatsuka, T. P. A. Akesson, E. Akilli, Flavia de Almeida Dias, Geert-Jan Besjes, Milena Bajic, Mogens Dam, Gorm Aske Gram Krohn Galster, Alejandro Alonso Diaz, Jørgen Beck Hansen, Peter Henrik Hansen, Jørn Dines Hansen, James William Monk, hqz214 hqz214, Simon Holm Stark, Troels Christian Petersen, Graig Wiglesworth, Stefania Xella, ATLAS

Experimental Particle Physics

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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 |λ_tcH| and |λ_tuH| couplings are 0.064 (0.055) and 0.066 (0.055), respectively.[Figure not available: see fulltext.]

Original language	English
Article number	123
Journal	The Journal of High Energy Physics
Volume	2019
Issue number	5
Number of pages	67
ISSN	1126-6708
DOIs	https://doi.org/10.1007/JHEP05(2019)123
Publication status	Published - 21 May 2019

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Aaboud, M., Aad, G., Abbott, B., Abdinov, O., Abeloos, B., Abhayasinghe, DK., Abidi, S. H., AbouZeid, O. S. A., Abraham, NL., Abramowicz, H., Abreu, H., Abulaiti, Y., Acharya, B. S., Adachi, S., Adamczyk, L., Adelman, J., Adersberger, M., Adiguzel, A., Adye, T., ... ATLAS (2019). Search for top-quark decays t -> Hq with 36 fb(-1) of pp collision data at root s=13 TeV with the ATLAS detector. The Journal of High Energy Physics, 2019(5), Article 123. https://doi.org/10.1007/JHEP05(2019)123

Aaboud, M, Aad, G, Abbott, B, Abdinov, O, Abeloos, B, Abhayasinghe, DK, Abidi, SH, AbouZeid, OSA, Abraham, NL, Abramowicz, H, Abreu, H, Abulaiti, Y, Acharya, BS, Adachi, S, Adamczyk, L, Adelman, J, Adersberger, M, Adiguzel, A, Adye, T, Affolder, AA, Afik, Y, Agheorghiesei, C, Aguilar-Saavedra, JA, Ahmadov, F, Aielli, G, Akatsuka, S, Akesson, TPA, Akilli, E, de Almeida Dias, F, Besjes, G-J, Bajic, M, Dam, M, Galster, GAGK, Alonso Diaz, A, Hansen, JB , Hansen, PH , Hansen, JD, Monk, JW, hqz214, H, Stark, SH, Petersen, TC , Wiglesworth, G , Xella, S & ATLAS 2019, 'Search for top-quark decays t -> Hq with 36 fb(-1) of pp collision data at root s=13 TeV with the ATLAS detector', The Journal of High Energy Physics, vol. 2019, no. 5, 123. https://doi.org/10.1007/JHEP05(2019)123

@article{4f3fec4830f14b4ea7fec916e672bfbd,

title = "Search for top-quark decays t -> Hq with 36 fb(-1) of pp collision data at root s=13 TeV with the ATLAS detector",

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.]",

author = "M. Aaboud and G. Aad and B. Abbott and O. Abdinov and B Abeloos and DK Abhayasinghe and S.H. Abidi and AbouZeid, {Ossama Sherif Alexander} and NL Abraham and H. Abramowicz and H. Abreu and Y. Abulaiti and B.S. Acharya and Sosuke Adachi and L. Adamczyk and J. Adelman and M. Adersberger and A. Adiguzel and T. Adye and Affolder, {A. A.} and Y. Afik and C. Agheorghiesei and Aguilar-Saavedra, {J. A.} and F. Ahmadov and G. Aielli and S. Akatsuka and Akesson, {T. P. A.} and E. Akilli and {de Almeida Dias}, Flavia and Geert-Jan Besjes and Milena Bajic and Mogens Dam and Galster, {Gorm Aske Gram Krohn} and {Alonso Diaz}, Alejandro and Hansen, {J{\o}rgen Beck} and Hansen, {Peter Henrik} and Hansen, {J{\o}rn Dines} and Monk, {James William} and hqz214 hqz214 and Stark, {Simon Holm} and Petersen, {Troels Christian} and Graig Wiglesworth and Stefania Xella and ATLAS",

year = "2019",

month = may,

day = "21",

doi = "10.1007/JHEP05(2019)123",

language = "English",

volume = "2019",

journal = "The Journal of High Energy Physics",

issn = "1126-6708",

publisher = "Springer",

number = "5",

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TY - JOUR

T1 - Search for top-quark decays t -> Hq with 36 fb(-1) of pp collision data at root s=13 TeV with the ATLAS detector

AU - Aaboud, M.

AU - Aad, G.

AU - Abbott, B.

AU - Abdinov, O.

AU - Abeloos, B

AU - Abhayasinghe, DK

AU - Abidi, S.H.

AU - AbouZeid, Ossama Sherif Alexander

AU - Abraham, NL

AU - Abramowicz, H.

AU - Abreu, H.

AU - Abulaiti, Y.

AU - Acharya, B.S.

AU - Adachi, Sosuke

AU - Adamczyk, 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 - Akesson, T. P. A.

AU - Akilli, E.

AU - de Almeida Dias, Flavia

AU - Besjes, Geert-Jan

AU - Bajic, Milena

AU - Dam, Mogens

AU - Galster, Gorm Aske Gram Krohn

AU - Alonso Diaz, Alejandro

AU - Hansen, Jørgen Beck

AU - Hansen, Peter Henrik

AU - Hansen, Jørn Dines

AU - Monk, James William

AU - hqz214, hqz214

AU - Stark, Simon Holm

AU - Petersen, Troels Christian

AU - Wiglesworth, Graig

AU - Xella, Stefania

AU - ATLAS

PY - 2019/5/21

Y1 - 2019/5/21

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.]

U2 - 10.1007/JHEP05(2019)123

DO - 10.1007/JHEP05(2019)123

M3 - Journal article

SN - 1126-6708

VL - 2019

JO - The Journal of High Energy Physics

JF - The Journal of High Energy Physics

IS - 5

M1 - 123

ER -

Search for top-quark decays t -> Hq with 36 fb(-1) of pp collision data at root s=13 TeV with the ATLAS detector

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