A recent analysis suggests that argon could be key to discerning the nature of a 248 keV recoil event observed in the LZ experiment, designed for dark matter searches. This event, which could be interpreted as the de-excitation of a pseudo-Dirac state or as the interaction of a Higgsino with halo particles, yields distinct predictions for detection in argon-based detectors. The ability to discriminate between these two interpretations lies in the interaction kinematics and nuclear form factors.

If the 248 keV signal in LZ is due to the de-excitation of a pseudo-Dirac state, a nuclear recoil line in argon is predicted at an energy of |δ|mχ/(mχ+mAr), which for a 200 GeV mass would be 336 keV. This signal would be expected at a rate ten times higher than that observed in xenon. Detecting this line and its energy, combined with the xenon data, would allow for the determination of the dark matter particle's mass. Conversely, if the event is the result of a ground-state Higgsino interacting with the fastest halo particles, no argon events would be expected, as the argon detection threshold would exceed the maximum halo particle energy.

The ratio between detection rates and recoil energies in xenon and argon depends solely on interaction kinematics and nuclear form factors, making it a robust test. Data already recorded by the DEAP-3600 experiment, which uses liquid argon, could contain tens of events if the pseudo-Dirac state hypothesis is correct. Analyzing these data, or conducting future argon experiments, would offer a direct path to confirm or refute these interpretations, shedding light on the nature of dark matter.