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The LUX-ZEPLIN dark matter experiment detected a nuclear recoil signal at approximately 248 keV energy, which researchers have analyzed through two supersymmetric particle physics models involving neutralino interactions with ordinary matter. The study proposes either elastic scattering via neutralinos with specific coupling configurations that avoid detection blind spots, or inelastic scattering involving pseudo-Dirac Higgsinos with small mass splittings generated by heavy particles at the PeV energy scale. Both theoretical frameworks can explain the observed signal while remaining consistent with current experimental constraints and predict different recoil patterns for future observations.
Why it matters
If confirmed, this detection could provide the first direct evidence of dark matter particles, which constitute approximately 85% of the universe's matter but have never been directly observed. The work helps constrain theoretical models of supersymmetry and guides future experimental searches by predicting distinguishable signatures for different dark matter candidates.
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⚠️ Preprint – Noch nicht peer-reviewed
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Abstract: The LUX-ZEPLIN (LZ) experiment has recently reported a nuclear-recoil candidate at $E_Rsimeq248$ 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 $X=|N_{13}|^2-|N_{14}|^2$ 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 $Xsim10^{-2}$. In the MSSM this favors low $tanbeta$, 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 $m_chisimeq500$ GeV and $Xsimeq0.007$, 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.
Source: Interpreting the High-Recoil LUX-ZEPLIN Event with Bino-/Singlino-like and Higgsino Dark Matter