title: Probing the Dark Sector with Dark Matter Bound States.
abstract: A model of the dark sector where O(few  GeV) mass dark matter particles χ couple to a lighter dark force mediator V, m_{V}≪m_{χ}, is motivated by the recently discovered mismatch between simulated and observed shapes of galactic halos. Such models, in general, provide a challenge for direct detection efforts and collider searches. We show that for a large range of coupling constants and masses, the production and decay of the bound states of χ, such as 0^{-+} and 1^{--} states, η_{D} and ϒ_{D}, is an important search channel. We show that e^{+}e^{-}→η_{D}+V or ϒ_{D}+γ production at B factories for α_{D}>0.1 is sufficiently strong to result in multiple pairs of charged leptons and pions via η_{D}→2V→2(l^{+}l^{-}) and ϒ_{D}→3V→3(l^{+}l^{-}) (l=e,μ,π). The absence of such final states in the existing searches performed at BABAR and Belle sets new constraints on the parameter space of the model. We also show that a search for multiple bremsstrahlung of dark force mediators, e^{+}e^{-}→χχ[over ¯]+nV, resulting in missing energy and multiple leptons, will further improve the sensitivity to self-interacting dark matter.
authors.affiliation: Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Haipeng
authors.initials: H
authors.lastname: An
authors.affiliation: California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Bertrand
authors.initials: B
authors.lastname: Echenard
authors.affiliation: Department of Physics and Astronomy, University of Victoria, Victoria, British Columbia, V8P 1A1 Canada.|Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5, Canada.
authors.forename: Maxim
authors.initials: M
authors.lastname: Pospelov
authors.affiliation: Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang