A PQ-Symmetric High-Scale SUSY Interpretation of the LZ High-Energy Recoil

Abstract

The 248-keV nuclear-recoil-like event reported by LZ can be interpreted as near-threshold upscattering of 1.08-TeV thermal Higgsino dark matter. A neutral-Higgsino splitting of order $0.3$--$0.35$ MeV places the fixed weak-interaction cross section close to the observed LZ interval and implies electroweak gauginos at ${O}(10^7)$ GeV. This spectrum is compatible with gravity-mediated high-scale supersymmetry and a Kim--Nilles Peccei--Quinn sector. Although the GUT scale is predicted to be lower than the conventional one, proton decay is suppressed due to the high SUSY scale which also solves the conventional CP, flavor, gravitino and moduli problems. Indeed, proton decay may be probed in the future. The PQ symmetry lowers the Higgsino mass below the SUSY scale and also yields a QCD axion that solves the strong-$CP$ problem. If the axion and Higgsino constitute mixed dark matter, the halo-profile-dependent H.E.S.S. limit can be relaxed.