Argon as the test of two interpretations of the LZ 248 keV recoil

Abstract

Argon decides what the LZ 248 keV recoil is. Read as an excited pseudo-Dirac state dropping to its ground state, the event predicts a nuclear-recoil line in argon at |δ|\,m_χ/(m_χ+m_{\rm Ar}), 336 keV at 200 GeV, at ten times the xenon rate, and the two line positions fix the mass. Read as a ground-state Higgsino lifted by the fastest halo particles, it predicts no argon events, since the argon threshold exceeds the halo maximum. The ratio depends only on kinematics and form factors, and the DEAP-3600 data already recorded hold tens of expected events.