Rare decay of the top quarkt→cll¯and single top quark production at the ILC

Abstract

We perform a complete and detailed analysis of the flavor changing neutral current rare top quark decays $t\ensuremath{\rightarrow}c{l}^{+}{l}^{\ensuremath{-}}$ and $t\ensuremath{\rightarrow}c{\ensuremath{\nu}}_{i}{\overline{\ensuremath{\nu}}}_{i}$ at one-loop level in the standard model, two Higgs doublet models (I and II), and in minimal supersymmetric standard model (MSSM). The branching ratios are very small in all models, $\mathcal{O}({10}^{\ensuremath{-}14})$, except for the case of the unconstrained MSSM, where they can reach $\mathcal{O}({10}^{\ensuremath{-}6})$ for ${e}^{+}{e}^{\ensuremath{-}}$, ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$, and ${\ensuremath{\nu}}_{i}{\overline{\ensuremath{\nu}}}_{i}$, and $\mathcal{O}({10}^{\ensuremath{-}5})$ for ${\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$. This branching ratio is comparable to the ones for $t\ensuremath{\rightarrow}cV,\text{ }\text{ }cH$. We also study the production rates of single top and the forward-backward asymmetry in ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}t\overline{c}$ and comment on the observability of such a signal at the International Linear Collider.