The nuclear physics of OHe
  A recent composite-dark-matter scenario assumes that the dominant fraction of
dark matter consists of O-helium (OHe) dark atoms, in which a lepton-like
doubly charged particle O is bound with a primordial helium nucleus. It
liberates the physics of dark matter from unknown features of new physics, but
it demands a deep understanding of the details of known nuclear and atomic
physics, which are still unclear. Here, we consider in detail the physics of
the binding of OHe to various nuclei of interest for direct dark matter
searches. We show that standard quantum mechanics leads to bound states in the
keV region, but does not seem to provide a simple mechanism that stabilizes
them. The crucial role of a barrier in the OHe-nucleus potential is confirmed
for such a stabilization.
