Dark Atoms of Dark Matter from New Stable Quarks and Leptons
  The nonbaryonic dark matter of the Universe can consist of new stable charged
leptons and quarks, if they are hidden in elusive "dark atoms" of composite
dark matter. Such possibility can be compatible with the severe constraints on
anomalous isotopes, if there exist stable particles with charge -2 and there
are no stable particles with charges +1 and -1. These conditions cannot be
realized in supersymmetric models, but can be satisfied in several recently
developed alternative scenarios. The excessive -2 charged particles are bound
with primordial helium in O-helium "atoms", maintaining specific
nuclear-interacting form of the Warmer than Cold Dark Matter. The puzzles of
direct dark matter searches appear in this case as a reflection of nontrivial
nuclear physics of O-helium.
