Di-Higgs production as a probe of flavor changing neutral Yukawa couplings

Abstract

Top partners are well motivated in many new physics models. Usually, vector like quarks, , are introduced to circumvent the quantum anomaly. Therefore, it is crucial to probe their interactions with standard model particles. However, flavor changing neutral couplings are always difficult to detect directly in current and future experiments. In this paper, we demonstrate how to constrain the flavor changing neutral Yukawa coupling indirectly, via the di-Higgs production. We consider the simplified model, including a pair of gauge singlet . Under the perturbative unitarity and experimental constraints, we select , and as benchmark points. After the analysis on the amplitude and evaluation of the numerical cross sections, we infer that the present constraints from di-Higgs production have already surpassed the unitarity bound because of the behavior. For the case of and , and can be bounded optimally in the range at the HL-LHC with CL. For the case of and , and can be bounded optimally in the range at the HL-LHC with CL. The anomalous triple Higgs coupling can also affect the constraints on . Finally, we determine that the top quark electric dipole moment can provide stronger bounds in the off-axis regions for some scenarios.