The top quark rare decays with flavor violation

Abstract

In the present study, we investigate the decays of the top quark $t\to c\gamma$, $t\to cg$, $t\to cZ$ and $t\to ch$. They are extremely rare processes in the Standard Model (SM). As the $U(1)$ extension of the minimal supersymmetric standard model (MSSM), the $U(1{)}_X$SSM features new superfields such as the right-handed neutrinos and three Higgs singlets. We analyze the effects of different sensitive parameters on the results and make reasonable theorecial predictions, which provides a useful reference for future experimental development. Considering the constraint of the updated experimental data, the numerical results show that the branching ratios of all four processes $t\to c\gamma ,cg,cZ,ch$ 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.

Comments: pages 25, figures 27