Can direct detection reach thermal higgsino dark matter above the fog?
In plain words
A leading heavy dark matter candidate, the higgsino from supersymmetry, would weigh about 1.1 TeV and interact very weakly with nuclei. The question is whether its scattering rate lies above the neutrino background where detectors can still find it.
Precise statement
For a nearly pure higgsino with thermal relic mass near 1.1 TeV, the spin-independent cross section $\sigma_{SI}$ comes from loop diagrams and from tree-level mixing suppressed by the bino and wino masses $M_1$, $M_2$. The question is $\sigma_{SI}$ as a function of $M_1$, $M_2$ and $\tan\beta$, including higher-order QCD and nuclear matrix-element uncertainties, compared with the xenon and argon neutrino-fog boundary at 1.1 TeV. An answer states for which gaugino masses a planned xenon or argon detector of about 1000 tonne-year exposure has $3\sigma$ discovery reach.
What would settle it
Extension of the heavy-WIMP effective theory NLO computation (Hill and Solon, Phys. Rev. D 91, 043505, 2015) to gaugino-mixed higgsinos, mapping $\sigma_{\mathrm{SI}}(M_1, M_2, \tan \beta)$ with hadronic uncertainties against the xenon and argon fog boundary at $1.1\,\mathrm{TeV}$.
Status in the literature
The pure-higgsino limit was computed at NLO by Hill and Solon (2015); the mixing-dependent reach is not mapped against the fog.