Direct detections of Majorana dark matter in vector portal.

In this paper we investigate the direct detections of Majorana dark matter (MDM) in vector portal. Considering that the tree-level scattering cross sections in these models are either dark matter velocity suppressed or spin-dependent, we calculate radiative corrections to the spin-independent cross section in effective field theory approach. Wilson coefficients of effective MDM-quark interactions are calculated at the one-loop level, and the Wilson coefficient of the effective MDM-gluon interaction is derived at the two-loop level. Numerical results show that current constraints can rule out a narrow mass range of MDM when tree-level contributions are considered, and the spin-independent cross section from radiative corrections is a few orders of magnitude smaller than the tree-level contributions. [ABSTRACT FROM AUTHOR]