Abstract
Dark matter candidates are one of the profound signatures of new physics, reflecting existence of new stable particles. If such particles are charged they can bind with ordinary electrons, forming anomalous isotopes. Severe constraints on the anomalous hydrogen exclude new stable single charged particles, but the case of stable double charged particles is not excluded so easily. Similar to ordinary baryonic matter dark matter candidates can be in the form of neutral dark atoms in which new stable or sufficiently long living double charged particles are bound by ordinary Coulomb interaction. In the most simple case only negative double charged particles are bound in O-helium (OHe) dark atoms with primordial helium. OHe hypothesis can provide the solution for puzzles of direct dark matter searches by specifics of OHe interaction in the matter of underground detectors. OHe interaction in the matter can lead to formation of various exotic forms of O-nuclearities. Provided that the mass of the double charged particle is around 1.25 TeV OHe hypothesis can explain the observed positron annihilation line excess in the galactic bulge by pair production in de-excitation of OHe atoms colliding in this region. In the model of Walking Technicolor generation of primordial excess of negatively charged techniparticles (over their antiparticles) can be related to the baryon asymmetry of the Universe, giving proper relationship of baryonic and non-baryonic matter densities. Such primordial excess may be accompanied by a subdominant excess of longliving positively double charged techniparticles, whose decay to same sign pair of leptons can explain the high energy cosmic positron anomaly, detected by PAMELA and AMS02. This explanation should be confronted with the cosmic gamma ray background measured by FERMI/LAT, what put upper limit on the mass of a decaying double charged particle. It makes search for stable double charged particles at the LHC a direct probe for composite dark matter hypothesis.
Highlights
The nature of cosmological dark matter, dominating in the matter content of the modern Universe, is related to new physics
Negative results of weakly interacting massive particles (WIMPs) searches appeal to other possible beyond the Standard model (BSM) solutions for the dark matter problem
If new stable species belong to non-trivial representations of the SU(2) electroweak group, sphaleron transitions at high temperatures can provide the relation between baryon asymmetry and excess of -2 charge stable species, as it was demonstrated in the case of Walking Technicolor (WTC) [5, 16]
Summary
The nature of cosmological dark matter, dominating in the matter content of the modern Universe, is related to new physics. (ii) Free positively charged particles are already suppressed in the early Universe and the abundance of anomalous helium in the Galaxy is negligible [12] Such a charge asymmetric solution appeals to possible relationship between asymmetric dark matter and baryon asymmetry of the ordinary matter. If new stable species belong to non-trivial representations of the SU(2) electroweak group, sphaleron transitions at high temperatures can provide the relation between baryon asymmetry and excess of -2 charge stable species, as it was demonstrated in the case of WTC [5, 16] After it is formed in the Standard Big Bang Nucleosynthesis (BBN), 4He screens the O−− charged particles in composite (4He++O−−) OHe “atoms” [12]. Following Khlopov [1], Bulekov et al [17], Gani et al [18], and Khlopov [19] we review main features of dark atom cosmology and possible direct and indirect probes for its physical basis
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