Top-quark rare decays with flavor violation* *This work is supported by the National Natural Science Foundation of China (12075074), the Natural Science Foundation of Hebei Province, China (A2020201002, A2022201022, A2022201017, A2023201040), the Natural Science Foundation of Hebei Education Department, China (QN2022173), the Post-graduate's Innovation Fund Project of Hebei University (HBU2024SS042), and the Youth Top-notch Talent Support Program of the Hebei

Abstract

In the present study, we investigated the decays of the top quark: , , , and . They are extremely rare processes in the standard model (SM). As the extension of the minimal supersymmetric standard model (MSSM), the SSM features new superfields such as the right-handed neutrinos and three Higgs singlets. We analyzed the effects of different sensitive parameters on the results and made reasonable theoretical predictions, thereby providing a useful reference for future experimental development. Considering the constraint set by the updated experimental data, the numerical results show that the branching ratios of the four processes, i.e., , can reach the same order of magnitude as their experimental upper limits. Among them, has the most evident effect on these processes and is the main parameter; , , , , , , and are also important parameters for the processes, and have effects on the numerical results.