  In the paper, we consider the processes of single top quark production in
association with dark matter particles through the t-channel in simplified
models with scalar and pseudoscalar mediators. Within the framework of these
models, we analyze the spin correlations that arise in the top quark production
process in association with dark matter, comparing them with the production of
a top quark in the Standard Model. We consider angular correlations of
kinematic variables, which define admissible regions in momentum space and can
be used experimentally to distinguish between the fraction of the total
momentum carried away by the scalar or pseudoscalar mediator.
