Probing the dark sector with dark matter bound states

A model of the dark sector where O(few GeV) mass dark matter particles χ couple to a lighter dark force mediator V, mVmχ, 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, ηD and D, is an important search channel. We show that e+e-→ηD+V or D+γ production at B factories for αD>0.1 is sufficiently strong to result in multiple pairs of charged leptons and pions via ηD→2V→2(l+l-) and 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+nV, resulting in missing energy and multiple leptons, will further improve the sensitivity to self-interacting dark matter.