Determine the nature of the LUX–ZEPLIN high-recoil event

Determine whether the high-recoil event reported by the LUX–ZEPLIN Collaboration is a statistical fluctuation or a possible signature of endothermic inelastic dark matter.

Background

The paper interprets a single LUX–ZEPLIN event at a nuclear-recoil energy of approximately 248 keV as potentially arising from endothermic inelastic dark matter. The proposed explanation requires a dark-matter mass above roughly 500 GeV and a mass splitting of order 300 keV, with a representative benchmark near 1.105 TeV and 350 keV.

Because the analysis is based on one event and an illustrative two-bin likelihood treatment, the interpretation remains unresolved. Additional LUX–ZEPLIN data are needed to establish whether the event reflects an ordinary statistical fluctuation or evidence for the inelastic dark-matter scenario; the planned CRESST upgrade offers a complementary test of the preferred parameter region.

References

Long-lived parent decays are mentioned as a possible source, while a quantitative realization is left open.

— Endothermic Dark Matter at LZ from a Decaying Parent  (2609.37545 - Jho et al., 29 Sep 2026) in Section 1, Introduction

Future LZ data will determine whether the reported event is a statistical fluctuation or a possible signature of inelastic dark matter, while the planned CRESST upgrade provides a complementary test of the preferred parameter region.

— Inelastic Dark Matter Signature at High Recoil Energy in LUX-ZEPLIN and CRESST  (2609.01475 - Su et al., 1 Sep 2026) in Conclusion

Interestingly, the origin of such an excess event remains unresolved from our known background arising from the SM interactions.

— Atmospheric neutrino up-scattering explanation of LZ 2026 excess  (2609.04185 - Jeesun et al., 3 Sep 2026) in Introduction, opening paragraph

A central caveat to our results, however, is that LZ does not publish the acceptance for WIMP-like events in this sideband; we assume unit acceptance, but if that is substantially lower it would relieve the tension we point out.

— Confronting the Higgsino Interpretation of the LZ Event with the High-Energy Sideband  (2609.04175 - Rodd et al., 3 Sep 2026) in Section 1 and Discussion

While we are unable to compare these results directly to LZ data, we find that solar observations are capable of sensitively probing this class of models.

— Solar Neutrino Constraints on Inelastic Dark Matter Scattering in Light of Recent LUX-ZEPLIN Observations  (2609.11833 - Nguyen et al., 10 Sep 2026) in Section 3, Section “Results” (discussion surrounding Fig. 4)

The key question is whether an $a$-mediated interaction can account for the high-energy event while remaining consistent with the low-energy recoil data.

— Can Nuclear Recoils and Solar Neutrinos Resolve the Composition of Singlino-Higgsino Dark Matter?  (2610.09753 - Lian et al., 7 Oct 2026) in Section “Elastic scattering with closed transitions”