Interpreting the High-Recoil LUX-ZEPLIN Event with Bino-/Singlino-like and Higgsino Dark Matter

The LUX-ZEPLIN (LZ) experiment has recently reported a nuclear-recoil candidate at E R 248 keV. We study two supersymmetric interpretations based on distinct neutralino couplings to the Z boson. In the elastic case, a bino- or singlino-like neutralino scatters through a diagonal axial Z coupling set by the Higgsino asymmetry X=N 13 2-N 14 squared rather than by the total Higgsino fraction. Since the spin-dependent blind spot does not coincide with the spin-independent one, Higgs-mediated scattering can be suppressed while retaining X about10-2. In the MSSM this favors low β, in tension with the observed Higgs mass for a few-TeV squark spectrum, a tension relieved by the tree-level quartic of the NMSSM. An explicit NMSSM benchmark with m χ 500 GeV and X 0.007, below current LZ limits, obtains its relic abundance from a singlet-like pseudoscalar resonance just above threshold, which also suppresses present-day annihilation. In the inelastic case, a pseudo-Dirac Higgsino scatters endothermically, with a splitting of a few hundred keV generated by gauginos at the PeV scale which can be lowered by opposite-sign bino-wino cancellation, or by weak singlino mixing; the minimal thermal realization is strongly constrained by solar-neutrino searches. The two mechanisms predict distinct recoil spectra away from the candidate.