Decaying dark atom constituents and cosmic positron excess

Abstract

We present a scenario where dark matter is in the form of dark atoms that can accommodate the experimentally observed excess of positrons in PAMELA and AMS-02 while being compatible with the constraints imposed on the gamma-ray ux from Fermi/LAT. This scenario assumes that the dominant component of dark matter is in the form of a bound state between a helium nucleus and a - 2 particle and a small component is in the form of a WIMP-like dark atom compatible with direct searches in underground detectors. One of the constituents of this WIMP-like state is a + 2 metastable particle with a mass of 1 TeV or slightly below that by decaying to e+ e+, μ+ μ+ and τ+ τ+ produces the observed positron excess. These decays can naturally take place via GUT interactions. If it exists, such a metastable particle can be found in the next run of LHC. The model predicts also the ratio of leptons over baryons in the universe to be close to - 3. © 2014 K. Belotsky et al.