Primordial heavy elements in composite dark matter models

A widely accepted viewpoint is to consider candidates for cosmological dark matter as neutral and weakly interacting particles, as well as to consider only light elements in the pregalactic chemical composition. It is shown that stable charged leptons and quarks can exist and, hidden in elusive atoms, play the role of dark matter. The inevitable consequence of realistic scenarios with such composite atom-like dark matter is existence of significant or even dominant fraction of "atoms", binding heavy -2 charged particles and He-4 nuclei. Being alpha-particles with shielded electric charge, such atoms catalyse a new path of nuclear transformations in the period of Big Bang Nucleosynthesis, which result in primordial heavy elements. The arguments are given, why such scenario escapes immediate contradiction with observations and challenges search for heavy stable charged particles in cosmic rays and at accelerators.Comment: Prepared for Proceedings of Blois2007 Conferenc

Probes for 4th generation constituents of dark atoms in Higgs boson studies at the LHC

The nonbaryonic dark matter of the Universe can consist of new stable charged species, bound in heavy neutral "atoms" by ordinary Coulomb interaction. Stable $\bar U$ (anti-$U$)quarks of 4th generation, bound in stable colorless ($\bar U \bar U \bar U$) clusters, are captured by the primordial helium, produced in Big Bang Nucleosynthesis, thus forming neutral "atoms" of O-helium (OHe), a specific nuclear interacting dark matter that can provide solution for the puzzles of direct dark matter searches. However, the existence of the 4th generation quarks and leptons should influence the production and decay rates of Higgs boson and is ruled out by the experimental results of the Higgs boson searches at the LHC, if the Higgs boson coupling to 4th generation fermions with is not suppressed. Here we argue that the difference between the three known quark-lepton families and the 4th family can naturally lead to suppression of this coupling, relating the accelerator test for such a composite dark matter scenario to the detailed study of the production and modes of decay of the 125.5 GeV boson, discovered at the LHC.Comment: Prepared for the Special issue "Dark atoms and dark radiation" of Advances in High Energy Physic

Remark on the minimal seesaw model and leptogenesis with tri/bi-maximal mixing

We have studied a leptogenesis scenario in the framework of the minimal seesaw model with tri/bi-maximal mixing. Usually, at least one of the elements in the Dirac mass matrix is fixed to be zero, for example, we denote it by $b_2=0$. We have pointed out that the absolute value of the CP asymmetry has several minimums and maximums with non-zero $b_2$. Thus one can expect that more rich phenomena, such as an enhanced leptogenesis, are hidden in the $b_2 \neq 0$ space.Comment: 9 pages, 7 figures, uses RevTex4. To appear in Physcal Review

Dark matter from stable charged particles?

Particle physics candidates for cosmological dark matter are usually considered as neutral and weakly interacting. However stable charged leptons and quarks can also exist and, hidden in elusive atoms, play the role of dark matter. The necessary condition for such scenario is absence of stable particles with charge -1 and effective mechanism for suppression of free positively charged heavy species. These conditions are realized in several recently developed scenarios. In scenario based on Walking Technicolor model excess of stable particles with charge -2 and the corresponding dark matter density is naturally related with the value and sign of cosmological baryon asymmetry. The excessive charged particles are bound with primordial helium in techni-O-helium "atoms", maintaining specific nuclear-interacting form of dark matter. Some properties of techni-O-helium Universe are discussed.Comment: Invited contribution to the book "Einstein and Hilbert: Dark Matter", Ed. V.Dvoeglazo