Leading loop effects in pseudoscalar-Higgs portal dark matter

We examine a model with a fermionic dark matter candidate having pseudoscalar interaction with the standard model particles where its direct detection elastic scattering cross section at tree level is highly suppressed. We then calculate analytically the leading loop contribution to the spin independent scattering cross section. It turns out that these loop effects are sizable over a large region of the parameter space. Taking constraints from direct detection experiments, the invisible Higgs decay measurements, observed DM relic density, we find viable regions which are within reach in the future direct detection experiments such as XENONnT.