Constraining the flavor changing Higgs couplings to the top-quark at the LHC

Abstract

Abstract:We study the flavor-changing couplings of the Higgs-boson with the top-quark using the processes: (a) pp −→ tt, (b) pp −→tj, and, (c) pp −→tjh at the LHC in light of current discovery of a 126 GeV Higgs-Boson. Sensitivities for the flavor-changing couplings are estimated using the LHC data that was collected until spring 2013. It is found that the process (c) is the most capable of yielding the best upper bound on the flavor-changing couplings with 2σ level sensitivities of |ξ 2 tc + ξ 2 tu | 1/2 7.3 × 10 −3 and 2.9 × 10 −3 resulting from t → blν l , h → jj with the 7 TeV and 8 TeV centre-of-mass energies respectively using existing data from the LHC. The corresponding bounds from h → bb are worse by a factor of about 1.8.

Search for top quark decays t → qH with H → γγ using the ATLAS detector

“…Examples of such extensions are the quark-singlet model (QS) [18][19][20], two-Higgs-doublet models (2HDM) of type I, with explicit flavour conservation, and of type II, such as the minimal supersymmetric standard model (MSSM) [21][22][23][24][25][26][27]. In 2HDM without explicit flavour conservation (type III) [28][29][30][31][32][33][34][35][36], the tc(u)H couplings are present at tree level. For a review of the different models see ref.…”

Enhancing thj production from top-Higgs FCNC couplings

“…was reported by the CMS collaboration from a combination of the multilepton channel and the diphoton plus lepton channel [67]. Except for the widely studied t → qh decays, the importance of the single top+Higgs production pp → th in probing the top-Higgs FCNC couplings has been also emphasized in the recent theoretical studies [68][69][70][71][72][73]. 1 The recent reviews, see examples.…”

Exploring the top-Higgs FCNC couplings at polarized linear colliders with top spin observables

“…Combining the analysis of the different Higgs decay channels, based at √ s = 8 TeV and an integrated luminosity of 20.3 (19.7) fb −1 , the 95% CL upper limits obtained by ATLAS (CMS) [10,12] are Br(t → cH) ≤ 4.6(4.0) × 10 −3 and Br(t → uH) ≤ 4.5(5.5) × 10 −3 . On the phenomenological side the sensitivity of LHC measurements to these non-standard flavor violating couplings in the top sector has been explored in great details, considering (a) the top quark pair production [13][14][15][16], (b) the single top + Higgs production [3,17] and (c) single top + W production [18]. The analysis of the tqH coupling has also been carried out in the context of the next generation e − e + linear colliders, the International Linear Collider (ILC) and the Compact Linear Collider (CLIC) [19,20].…”

“…The additional FCNC decay processes give positive contributions to Γ t , proportional to (| g tq | 2 + | g qt | 2 ) and from the experimentally observed Γ t an upper bound on | g tq | 2 + | g qt | 2 can be obtained. These flavor changing couplings can also lead to the three body decay h → t * (→ W + b)q, where top is produced off-shell and q = u, c. Then total width of the Higgs gets modified and the couplings g tq , g qt can be independently constrained from the measurement of the Higgs decay width at the LHC [14].…”