Dark Baryogenesis

Abstract

We first suggested a scenario in which a generic, dark chiral gauge group undergoes a first order phase transition in order to generate the observed baryon asymmetry in the universe, provide a viable dark matter candidate and explain the observed baryon-to-dark matter ratio of relic abundances [arXiv:1003.0899]. We now provide a model in which a copy of the electroweak gauge group is added to the Standard Model. We spontaneously break this new gauge group to the diagonal Z_2 center which is used to stabilize a dark matter candidate. In addition to the dark matter candidate, anomaly free messenger fermions are included which transform non-trivially under all the gauge groups. In analogy to electroweak baryogenesis, the model generates an excess of messenger "baryons". These "baryons" subsequently decay to the Standard Model and dark matter to generate an excess of Standard Model baryons. The baryon-to-dark matter number density ratio is ultimately due to the requirement of gauge anomaly freedom. Dark sphalerons generate operators which violate B - L but preserves B + L. Thus, the asymmetry is not washed out by the Standard Model. The model radiatively generates a dark matter mass of order of the electroweak vacuum expectation value suppressed by a loop factor therefore setting the dark matter-to-baryon relic abundance. We outline some distinctive experimental signatures and ensure these models are consistent with existing constraints. As first discussed in [arXiv:0907.3142], these dark matter scenarios feature long-lived particles which can be observed at colliders. We finally show how approximate global symmetries in the higgs sector stabilize both the dark and electroweak scales thereby mitigating the hierarchy problem. Light dark higgses are needed to ensure the correct relic abundance. Thus, by construction the SM and dark higgses generate masses at two- and three-loops, respectively.