Abstract
With the deeper study of Higgs particle, Higgs precision measurements can be served to probe new physics indirectly. In many new physics models, vector-like quarks $T_L,~T_R$ occur naturally. It is important to probe their couplings with standard model particles. In this work, we consider the singlet $T_L,~T_R$ extended models and show how to constrain the $Tth$ couplings through the $h\rightarrow\gamma Z$ decay at high-luminosity LHC. Firstly, we derive the perturbative unitarity bounds on $|y_{L,~R}^{tT}|$ with other couplings set to be zeros simply. To optimize the situation, we take $m_T$ = 400 GeV and $s_L$ = 0.2 considering the experimental constraints. Under this benchmark point, we find that the future bounds from $h\rightarrow\gamma Z$ decay can limit the real parts of $y_{L,~R}^{tT}$ in the positive direction to be O(1) because of the double enhancement. For the real parts of $y_{L,~R}^{tT}$ in the negative direction, it is always surpassed by the perturbative unitarity. Moreover, we find that the top quark electric dipole moment can give stronger bounds (especially the imaginary parts of $y_{L,~R}^{tT}$) than the perturbative unitarity and $h\rightarrow\gamma Z$ decay in the off-axis regions for some scenarios.
Highlights
The standard model (SM) of elementary particle physics was proposed in the 1960s [1], and it has been verified up to now to be quite successful
It is strongly constrained for the mixings between heavy particles and the first two generations because of the bounds from flavor physics [17,18,19]
Let us start with the model by adding a pair of singlet fermions TL, TR to the SM, which is dubbed as the VLQT model
Summary
The standard model (SM) of elementary particle physics was proposed in the 1960s [1], and it has been verified up to now to be quite successful. Many of these BSM models predict the existence of heavy fermions, for example, composite Higgs models [2,3], little Higgs models [4,5], grand unified theories [6], and extra-dimension models [7] In these models, there can be a heavy up-type quark T, which interacts with the SM particles through TbW; TtZ; Tth interactions. There can be a heavy up-type quark T, which interacts with the SM particles through TbW; TtZ; Tth interactions Analyses on these couplings may tell us some clues about the new physics.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have