Relic Density Of Dark Matter In The Inert Doublet Model Beyond Leading Order For The Low Mass Region. Ii. Coannihilation

We examine the relic density of the light mass dark matter region in the inert doublet model (IDM) when the dominant process is due to coannihilation between the lightest neutral scalars of the model. The full one-loop electroweak corrections are computed in an on shell scheme and are found to be well approximated as an effective cross section expressed in terms of Z observables. The elcetroweak corrections to the subdominant process, which consists of an annihilation into an on shell W and an off shell W, that is calculated as a annihilation into a three-body final state, is also performed. In the calculation of the latter in this case of coannihilation, although the SM Higgs exchange is absent, it is induced at one loop, but the cross section does not show a peak behavior despite the crossing of the Higgs resonance. This cross section reveals an important dependence on a parameter that describes the self-interaction of the new scalars (solely within the dark sector), a parameter which is not accessible in tree-level calculations of standard model-IDM interactions.