Abstract
The inelastic dark matter model is one kind of popular models for the light dark matter (DM) below O(1) GeV. If the mass splitting between DM excited and ground states is small enough, the co-annihilation becomes the dominant channel for thermal relic density and the DM excited state can be long-lived at the collider scale. We study scalar and fermion inelastic dark matter models for mathcal{O} (1) GeV DM at Belle II with U(1)D dark gauge symmetry broken into its Z2 subgroup. We focus on dilepton displaced vertex signatures from decays of the DM excited state. With the help of precise displaced vertex detection ability at Belle II, we can explore the DM spin, mass and mass splitting between DM excited and ground states. Especially, we show scalar and fermion DM candidates can be discriminated and the mass and mass splitting of DM sector can be determined within the percentage of deviation for some benchmark points. Furthermore, the allowed parameter space to explain the excess of muon (g− 2)μ is also studied and it can be covered in our displaced vertex analysis during the early stage of Belle II experiment.
Highlights
The null signal result from direct detection provides severe bounds on the cross section of dark matter (DM) and nuclear scattering above a few GeV [4,5,6]
If the mass splitting between DM excited and ground states is small enough, the co-annihilation becomes the dominant channel for thermal relic density and the DM excited state can be long-lived at the collider scale
We study scalar and fermion inelastic dark matter models for O(1) GeV DM at Belle II with U(1)D dark gauge symmetry broken into its Z2 subgroup
Summary
The scalar and fermion inelastic (or excited) DM models with U(1)D gauge symmetry are reviewed . We consider a dark sector with two singlet complex scalars Φ and φ = (φ2 + iφ1)/ 2 as the dark Higgs and dark matter sectors, respectively. We consider a dark sector with the singlet complex scalar Φ and Dirac fermion χ as the dark Higgs and dark matter sectors, respectively. Both Φ and χ are charged under U(1)D, but neutral of the SM gauge symmetry. For the partial decay width of φ2(χ2) → φ1(χ1)π+π−, we rescale the partial decay width of φ2(χ2) → φ1(χ1)μ+μ− with the measured R(s) values in ref. [68]
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