Blind Spots for neutralino Dark Matter in the MSSM with an intermediate m_A

We study the spin-independent neutralino Dark Matter scattering off heavy nuclei in the MSSM. We identify analytically the blind spots in direct detection for intermediate values of $m_A$. In the region where $\mu$ and $M_{1,2}$ have opposite signs, there is not only a reduction of the lightest CP-even Higgs coupling to neutralinos, but also a destructive interference between the neutralino scattering through the exchange of the lightest CP-even Higgs and that through the exchange of the heaviest CP-even Higgs. At critical values of $m_A$, the tree-level contribution from the light Higgs exchange cancels the contribution from the heavy Higgs, so the scattering cross section vanishes. We denote these configurations as blind spots, since they provide a generalization of the ones previously discussed in the literature, which occur at very large values of $m_A$. We show that the generalized blind spots may occur in regions of parameter space that are consistent with the obtention of the proper neutralino relic density, and can be tested by non-standard Higgs boson searches and EWino searches at the LHC and future linear colliders.