Single Top Production in $e^{+}{e}^{-}$, $e^{-}{e}^{-}$, $\gamma e$ and $\gamma \gamma$ Collisions

Abstract

Single top quark cross section evaluations for the complete sets of tree-level diagrams in the $e^{+}{e}^{-}$, $e^{-}{e}^{-}$, $\gamma e$ and $\gamma \gamma$ modes of the next linear collider with unpolarized and polarized beams are performed within the Standard Model and beyond. From comparison of all possibilities we conclude that the process ${\gamma }_{+}{e}_L^{-}\to e^{-}t\bar{b}$ is extremely favoured due to large cross section, no $t\bar{t}$ background, high degrees of beam polarization, and exceptional sensitivities to $V_{tb}$ and anomalous $Wtb$ couplings. Similar reasons favour the process $e^{-}{e}^{-}\to e^{-}{\nu }_e\bar{t}b$ for probing top quark properties despite a considerably lower cross section. Less favourable are processes like $e^{+}{e}^{-},\gamma \gamma \to e^{-}{\nu }_{e}t\bar{b}$. Three processes were chosen to probe their sensitivity to anomalous $Wtb$ couplings, with best bounds found for ${\gamma }_{+}{e}_L^{-}\to e^{-}t\bar{b}$ and $e_R^{+}{e}_R^{-}\to e^{-}{\nu }_{e}t\bar{b}$.

Comments: 23 pages, 13 figures