title: Gauge coupling unification and nonequilibrium thermal dark matter.
abstract: We study a new mechanism for the production of dark matter in the Universe which does not rely on thermal equilibrium. Dark matter is populated from the thermal bath subsequent to inflationary reheating via a massive mediator whose mass is above the reheating scale T(RH). To this end, we consider models with an extra U(1) gauge symmetry broken at some intermediate scale (M(int) ≃ 10(10)-10(12) GeV). We show that not only does the model allow for gauge coupling unification (at a higher scale associated with grand unification) but it can provide a dark matter candidate which is a standard model singlet but charged under the extra U(1). The intermediate scale gauge boson(s) which are predicted in several E6/SO(10) constructions can be a natural mediator between dark matter and the thermal bath. We show that the dark matter abundance, while never having achieved thermal equilibrium, is fixed shortly after the reheating epoch by the relation T(RH)(3)/M(int)(4). As a consequence, we show that the unification of gauge couplings which determines M(int) also fixes the reheating temperature, which can be as high as T(RH) ≃ 10(11) GeV.
authors.affiliation: Laboratoire de Physique Théorique Université Paris-Sud, F-91405 Orsay, France.
authors.forename: Yann
authors.initials: Y
authors.lastname: Mambrini
authors.affiliation: William I. Fine Theoretical Physics Institute, School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: Keith A
authors.initials: KA
authors.lastname: Olive
authors.affiliation: Laboratoire de Physique Théorique Université Paris-Sud, F-91405 Orsay, France.
authors.forename: Jérémie
authors.initials: J
authors.lastname: Quevillon
authors.affiliation: Instituto de Fisica Teorica, IFT-UAM/CSIC, 28049 Madrid, Spain.
authors.forename: Bryan
authors.initials: B
authors.lastname: Zaldívar