Fermionic Dark Matter and New Scalar Production in $e^+e^- \to H^+H^-$ at Colliders
We investigate the pair production process $e^+e^- \to H^+H^-$ in the framework of the scotogenic model. The production mechanism receives contributions at tree level from photon and $Z$-boson exchange, as well as from $t$-channel exchange of the new singlet right-handed fermions $N_{1,2,3}$. where neutrino masses are generated radiatively and one of the singlet right-handed fermions serves as a viable dark matter candidate. We evaluate the individual contributions of these diagrams and compute the total production cross section after imposing all relevant theoretical and experimental constraints on the model parameters, including those associated with dark matter relic abundance and direct detection limits. Our results demonstrate that the dominant contribution to the cross section originates from the exchange of the singlet fermions $N_{1,2,3}$, particularly from the dark matter component of the spectrum. In addition, we examine the dependence of the cross section on the center-of-mass energy for several benchmark scenarios in the allowed parameter space. These predictions can be probed at future high-energy $e^+e^-$ colliders, providing a sensitive test of the scotogenic framework and the role of fermionic dark matter, as well as enabling more stringent constraints on the model parameters.