A Vector-Like Lepton Interpretation of the High-Energy Nuclear Recoil Candidate in LUX-ZEPLIN

The LUX-ZEPLIN (LZ) experiment has recently reported a nuclear-recoil candidate at E R=248 plus or minus23 stat plus or minus23 sys, keV in an exposure of 2.84, tonne,yr. At this unusually high recoil energy, the spin-independent (SI) xenon response is strongly suppressed, motivating dark matter interactions with a harder recoil spectrum. We show that elastic spin-dependent (SD) scattering through the nonrelativistic operator O 4= S DM times S N provides a simple realization of such a spectrum. We consider singlet-doublet Majorana dark matter, for which a diagonal Z coupling generates the required SD interaction. The accompanying Higgs-mediated SI interaction would generically produce too many low-energy recoils, but can be suppressed along a Higgs blind spot while retaining a nonzero Z coupling. We find a region of the Higgs blind spot that simultaneously predicts an O(1) event rate in the LZ high-recoil window and reproduces the observed thermal relic abundance. The same SD interaction leads to solar capture, allowing this region to be tested independently with solar-neutrino searches. Current IceCube limits already probe part of the LZ-compatible thermal parameter space, while a viable region remains. Additional xenon exposure and improved solar-neutrino searches can therefore provide complementary tests of this interpretation.