Self-interacting scalar dark matter with local Z₃symmetry

We construct a self-interacting scalar dark matter (DM) model with local discrete Z 3 symmetry that stabilizes a weak scale scalar dark matter X . The model assumes a hidden sector with a local U(1) X dark gauge symmetry, which is broken spontaneously into Z 3 subgroup by nonzero VEV of dark Higgs field ϕ X (⟨ ϕ X ⟩≠0). Compared with global Z 3 DM models, the local Z 3 model has two new extra fields: a dark gauge field Z ' and a dark Higgs field ϕ (a remnant of the U(1) X breaking). After imposing various constraints including the upper bounds on the spin-independent direct detection cross section and thermal relic density, we find that the scalar DM with mass less than 125 GeV is allowed in the local Z 3 model, in contrary to the global Z 3 model. This is due to new channels in the DM pair annihilations open into Z ' and ϕ in the local Z 3 model. Most parts of the newly open DM mass region can be probed by XENON1T and other similar future experiments. Also if ϕ is light enough (a few MeV ≲ m ϕ ≲ O(100) MeV), it can generate a right size of DM self-interaction and explain the astrophysical small scale structure anomalies. This would lead to exotic decays of Higgs boson into a pair of dark Higgs bosons, which could be tested at LHC and ILC.