Flavour-changing top decays in the aligned two-Higgs-doublet model

Abstract

We perform a complete one-loop computation of the two-body flavour-changing top decays t → ch and t → cV (V = γ, Z), within the aligned two-Higgs-doublet model. We evaluate the impact of the model parameters on the associated branching ratios, taking into account constraints from flavour data and measurements of the Higgs properties. Assuming that the 125 GeV Higgs corresponds to the lightest CP-even scalar of the CP-conserving aligned two-Higgs-doublet model, we find that the rates for such flavour-changing top decays lie below the expected sensitivity of the future high-luminosity phase of the LHC. Measurements of the Higgs signal strength in the di-photon channel are found to play an important role in limiting the size of the t → ch decay rate when the charged scalar of the model is light.

Flavour-changing top decays in the aligned two-Higgs-doublet model

“…We obtain the upper bounds on Br(t → cV ) (V = γ, Z) and Br(t → ch) for benchmark values of the charged Higgs mass shown in table 1 [20]. The direct searches of a charged Higgs at the LHC via top decays put stringent limits on the parameter ς d within the mass range 90 GeV < M H ± < 150 GeV, providing |ς d | 10.…”

“…Now, we present our results of the flavour-changing top-quark decays t → ch and t → cV (V = γ, Z) [20]. We have computed them in the Feynman gauge and have checked the gauge independence by additionally performing all calculations in the unitary gauge.…”

“…saturates either the h → 2γ limits or the perturbativity bound [20]. Prior to the Higgs discovery, it was found that a light charged Higgs could enhance considerably the decay rate of t → ch within the type-II 2HDM for large values of tan β and the cubic…”

“…Top FCNC decays Gauhar Abbas Table 1: Upper bounds on Br(t → cV ) (V = γ, Z) and Br(t → ch) in the CP-conserving A2HDM [20]. Higgs coupling λ h H + H − , and even touch the level of the expected sensitivity at the high luminosity LHC: Br(t → ch) ∼ 10 −5 [36,37].…”

“…In this article, we present our investigations on the flavour-changing top-quark decays t → ch and t → cV (V = γ, Z), within the framework of the CP-conserving A2HDM [20]. These decays are highly suppressed in the SM due to the GIM mechanism and occur only at the loop level.…”