Identifying the nature of dark matter at e- e+ colliders

In this work, we consider the process e(+) + e(-) -> b (b) over bar + is not an element of(T), at the future electron-positron colliders such as the International Linear Collider and Compact Linear Collider, to look for the dark matter (DM) effect and identify its nature at two different center-of-mass energies E-c.m. = 500 GeV and 1 TeV. For this purpose, we take two extensions of the standard model, in which the DM could be a real scalar or a heavy right-handed neutrino (RHN) similar to many models motivated by neutrino mass. In the latter extension, the charged leptons are coupled to the RHNs via a lepton flavor violating interaction that involves a charged singlet scalar. After discussing different constraints, we define a set of kinematical cuts that suppress the background and generate different distributions that are useful in identifying the DM nature. The use of polarized beams (like the polarization P(e(-), e(+)) = [+0.8, -0.3] at the International Linear Collider) makes the signal detection easier and the DM identification more clear, where the statistical significance gets enhanced by twice (five times) for scalar (RHN) DM.