Direct Detection of the Wino- and Higgsino-like Neutralino Dark Matters at One-Loop Level

The neutralino-nucleon ($\tilde{\chi}^0$-$N$) scattering is an important process for direct dark matter searches. The tree-level neutralino-nucleon scattering mediated by one Higgs or $Z$ boson exchange is suppressed in a pure gaugino or Higgsino limit. The one-loop corrections to the scattering cross section may not be neglected when the tree-level cross section is as close as the proposed sensitivities of the future search experiments. In this paper we discuss the one-loop contribution to the neutralino-nucleon scattering mediated by $W$ or $Z$ boson exchange for a wino- or Higgsino-like LSP. The contribution is not suppressed by any SUSY particle mass or mixing. The correction may significantly alter the tree-level cross section when $\sigma_{\tilde{\chi}^0 N}\sim 10^{-45}$ cm$^{2}$ or less.