Search for flavour-changing neutral current top quark decays $t\to Hq$ in $pp$ collisions at $\sqrt{s}=8$ TeV with the ATLAS detector

G. Aad; M.K. Ayoub; A. Bassalat; C. Bécot; S. Binet; C. Bourdarios; D. Delgove; J-B. de Vivie De Regie; L. Duflot; M. Escalier; L. Fayard; D. Fournier; E.L. Gkougkousis; J-F. Grivaz; T. Guillemin; F. Hariri; S. Henrot-Versille; J. Hrivnac; L. Iconomidou-Fayard; M. Kado; A. Lounis; N. Makovec; N. Morange; C. Nellist; P. Petroff; L. Poggioli; P. Puzo; A. Renaud; D. Rousseau; G. Rybkin; A.C. Schaffer; E. Scifo; L. Serin; S. Simion; R. Tanaka; D. Zerwas; Zhongkai Zhang; Y. Zhao; Z. Barnovska; N. Berger; M. Delmastro; L. Di Ciaccio; S. Elles; T. Hryn’ova; S. Jézéquel; I. Koletsou; R. Lafaye; J. Leveque; P. Mastrandrea; G. Sauvage; E. Sauvan; O. Simard; T. Todorov; E. Yatsenko; I. Wingerter-Seez; L. Alio; M. Barbero; Y. Coadou; C. Diaconu; S. Diglio; F. Djama; O. Duccu; L. Feligioni; J. Gao; G.D. Hallewell; F. Hubaut; S.J. Kahn; E. B. F. G. Knoops; E. Le Guirriec; J. Liu; K. Liu; D. Madaffari; K. Mochizuki; E. Monnier; S. Muanza; Y. Nagai; E. Nagy; P. Pralavorio; A. Rozanov; T. Serre; M. Talby; R.E. Ticse Torres; E. Tiouchichine; S. Tisserant; J. Toth; F. Touchard; L. Vacavant; S. Albrand; J. Collot; S. Crépé-Renaudin; P.A. Delsart; C. Gabaldon; M.H. Genest; J.Y. Hostachy; F. Ledroit-Guillon; A. Lleres; A. Lucotte; F. Malek; C. Monini; J. Stark; B. Trocmé; M. Wu; D. Boumediene; E. Busato; D. Calvet; S. Calvet; J. Donini; E. Dubreuil; G. Gilles; Ph. Gris; H. Liao; R. Madar; D. Pallin; S.M. Romano Saez; C. Santoni; D. Simon; T. Theveneaux-Pelzer; F. Vazeille

doi:10.1007/JHEP12(2015)061

Journal articles

Search for flavour-changing neutral current top quark decays $t\to Hq$ in $pp$ collisions at $\sqrt{s}=8$ TeV with the ATLAS detector

G. Aad ¹ M.K. Ayoub ² A. Bassalat ² C. Bécot ² S. Binet ² C. Bourdarios ² D. Delgove ² J-B. de Vivie De Regie ² L. Duflot ² M. Escalier ² L. Fayard ² D. Fournier ² E.L. Gkougkousis ² J-F. Grivaz ² T. Guillemin ² F. Hariri ² S. Henrot-Versille ² J. Hrivnac ² L. Iconomidou-Fayard ² M. Kado ² A. Lounis ² N. Makovec ² N. Morange ² C. Nellist ² P. Petroff ² L. Poggioli ² P. Puzo ² A. Renaud ² D. Rousseau ² G. Rybkin ² A.C. Schaffer ² E. Scifo ² L. Serin ² S. Simion ² R. Tanaka ² D. Zerwas ² Zhongkai Zhang ² Y. Zhao ² Z. Barnovska ³ N. Berger ³ M. Delmastro ³ L. Di Ciaccio ³ S. Elles ³ T. Hryn’ova ³ S. Jézéquel ³ I. Koletsou ³ R. Lafaye ³ J. Leveque ³ P. Mastrandrea G. Sauvage ³ E. Sauvan ¹ O. Simard ³ T. Todorov ³ E. Yatsenko ³ I. Wingerter-Seez ³ L. Alio ¹ M. Barbero Y. Coadou ¹ C. Diaconu ¹ S. Diglio ¹ F. Djama ¹ O. Duccu ^{4, 1} L. Feligioni ¹ J. Gao ¹ G.D. Hallewell ¹ F. Hubaut ¹ S.J. Kahn ¹ E. B. F. G. Knoops ¹ E. Le Guirriec ¹ J. Liu ¹ K. Liu ¹ D. Madaffari ¹ K. Mochizuki ¹ E. Monnier ¹ S. Muanza ¹ Y. Nagai ¹ E. Nagy ¹ P. Pralavorio ¹ A. Rozanov ¹ T. Serre ¹ M. Talby ¹ R.E. Ticse Torres ¹ E. Tiouchichine ¹ S. Tisserant ¹ J. Toth ¹ F. Touchard ¹ L. Vacavant ¹ S. Albrand ⁵ J. Collot ⁵ S. Crépé-Renaudin ⁵ P.A. Delsart ⁵ C. Gabaldon ⁵ M.H. Genest ⁵ J.Y. Hostachy ⁵ F. Ledroit-Guillon ⁵ A. Lleres ⁵ A. Lucotte ⁵ F. Malek ⁵ C. Monini ⁵ J. Stark ⁵ B. Trocmé ⁵ M. Wu ⁵ D. Boumediene ⁶ E. Busato ⁶ D. Calvet ⁶ S. Calvet ⁶ J. Donini ⁶ E. Dubreuil ⁶ G. Gilles ⁶ Ph. Gris ⁶ H. Liao ⁶ R. Madar ⁶ D. Pallin ⁶ S.M. Romano Saez ⁶ C. Santoni ⁶ D. Simon ⁶ T. Theveneaux-Pelzer ⁶ F. Vazeille ⁶

1 CPPM - Centre de Physique des Particules de Marseille

2 LAL - Laboratoire de l'Accélérateur Linéaire

3 LAPP - Laboratoire d'Annecy de Physique des Particules

4 NIPNE - Horia Hulubei National Institute of Physics and Nuclear Engineering

5 LPSC - Laboratoire de Physique Subatomique et de Cosmologie

6 LPC - Laboratoire de Physique Corpusculaire - Clermont-Ferrand

Abstract : A search for flavour-changing neutral current decays of a top quark to an up-type quark ($q=u, c$) and the Standard Model Higgs boson, where the Higgs boson decays to $b\bar{b}$, is presented. The analysis searches for top quark pair events in which one top quark decays to $Wb$, with the $W$ boson decaying leptonically, and the other top quark decays to $Hq$. The search is based on $pp$ collisions at $\sqrt{s}=8$ TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider and uses an integrated luminosity of 20.3 fb$^{-1}$. Data are analysed in the lepton-plus-jets final state, characterised by an isolated electron or muon and at least four jets. The search exploits the high multiplicity of $b$-quark jets characteristic of signal events, and employs a likelihood discriminant that uses the kinematic differences between the signal and the background, which is dominated by $t\bar{t} \to WbWb$ decays. No significant excess of events above the background expectation is found, and observed (expected) 95% CL upper limits of 0.56% (0.42%) and 0.61% (0.64%) are derived for the $t\to Hc$ and $t\to Hu$ branching ratios respectively. The combination of this search with other ATLAS searches in the $H \to \gamma\gamma$ and $H\to WW^*, \tau\tau$ decay modes significantly improves the sensitivity, yielding observed (expected) 95% CL upper limits on the $t\to Hc$ and $t\to Hu$ branching ratios of 0.46% (0.25%) and 0.45% (0.29%) respectively. The corresponding combined observed (expected) upper limits on the $|\lambda_{tcH}|$ and $|\lambda_{tuH}|$ couplings are 0.13 (0.10) and 0.13 (0.10) respectively. These are the most restrictive direct bounds on $tqH$ interactions measured so far.

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Journal articles

Domain :

Physics [physics] / High Energy Physics - Experiment [hep-ex]

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http://hal.in2p3.fr/in2p3-01202985
Contributor : Sabine Starita <>
Submitted on : Tuesday, September 22, 2015 - 9:53:24 AM
Last modification on : Tuesday, April 20, 2021 - 12:00:15 PM

Search for flavour-changing neutral current top quark decays $t\to Hq$ in $pp$ collisions at $\sqrt{s}=8$ TeV with the ATLAS detector

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Search for flavour-changing neutral current top quark decays $t\to Hq$ in $pp$ collisions at $\sqrt{s}=8$ TeV with the ATLAS detector

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