The top quark rare decays with flavor violation

Abstract

In the present study, we investigate the decays of the top quark $t\rightarrow c\gamma$, $t\rightarrow cg$, $t\rightarrow cZ$ and $t\rightarrow ch$. They are extremely rare processes in the Standard Model (SM). As the $U(1)_X$ extension of the minimal supersymmetric standard model, the $U(1)_X$SSM features new superfields such as the right-handed neutrinos and three Higgs singlet states. We analyze the effects of different sensitivity parameters on the results and make reasonable theorecial predictions useful for future experimental developments. Considering the constraint of the updated experimental data, the numerical results show that the branching ratios of all four processes $t\rightarrow c\gamma,~cg,~cZ,~ch$ can reach the same order of magnitude as their experimental upper limits. Among them, $\tan\beta$ has the most obvious effect on each process and is the main parameter. $g_X$, $g_{YX}$, $\mu$, $M_2$, $\lambda_H$, $M_{U23}^2$ and $M_{Q23}^2$ are important parameters for the processes, and have effects on the numerical results.Comment: pages 22, figures 1