Dark Atoms and their decaying constituents
  The nonbaryonic dark matter of the Universe might consist of new stable
charged species, bound by ordinary Coulomb interactions in various forms of
heavy neutral "dark atoms". The existing models offer natural implementations
for the dominant and subdominant forms of dark atom components. In the
framework of Walking Technicolor the charge asymmetric excess of both stable
negatively doubly charged technilepton $\zeta^{--}$ and metastable but
longliving positively doubly charged technibaryon $UU^{++}$ can be generated in
the early Universe together with the observed baryon asymmetry. If the excess
of $\zeta$ exceeds by several orders of magnitude the excess of $UU$, dark
matter might consist dominantly by $He\zeta$ dark atoms of nuclear interacting
O-helium ($OHe$) bound state of $\zeta$ with primordial helium. Although
sparse, this subdominant component can lead to observable effects, since
leptonic decays of technibaryons $UU$ give rise to two positively charged
leptons contrary to the pairs of opposite charge leptons created in decays of
neutral particles. We show that decays of $UU^{++}\rightarrow e^+ e^+, \mu^+
\mu^+, \tau^+ \tau^+$ of the subdominant $UU\zeta$ component of dark matter,
can explain the observed high energy positron excess in the cosmic rays if the
fraction of $UU\zeta$ is $\sim 10^{-6}$ of the total dark matter density, the
mass of $UU^{++}$ about 1 TeV and the lifetime about $10^{20} $s. Optimizing
fit of recent AMS-02 data by model parameters, the predicted mass range of such
long-living double charge particle is challenging for its search at the LHC.
(abridged)
