Scalar dark matter (DM) can have dimensionful coupling to the Higgs boson—the soft portal into DM—which is predicted to be unsuppressed by the underlying $SO(10)$ grand unified theory (GUT). The dimensionful coupling can be large, $\mu /v\gg 1$, without spoiling the perturbativity of low energy theory up to the GUT scale. We show that the soft portal into DM naturally triggers radiative electroweak symmetry breaking (EWSB) via large 1-loop DM corrections to the effective potential. In this scenario, EWSB, the DM thermal freeze-out cross section, and DM scattering on nuclei are all dominated by the same coupling, predicting the DM mass range to be $700\mathrm{GeV}<M_{\mathrm{DM}}<2\mathrm{TeV}$. The spin-independent direct detection cross section is predicted to be just below the present experimental bounds.

• Received 18 December 2009

DOI:https://doi.org/10.1103/PhysRevLett.104.201301