Strong dark matter self-interaction from a stable scalar mediator

Abstract

In face of the small-scale structure problems of the collisionless cold dark matter (DM) paradigm, a popular remedy is to introduce a strong DM self-interaction which can be generated nonperturbatively by a MeV-scale light mediator. However, if such the mediator is unstable and decays into SM particles, the model is severely constrained by the DM direct and indirect detection experiments. In the present paper, we study a model of a self-interacting fermionic DM, endowed with a light stable scalar mediator. In this model, the DM relic abundance is dominated by the fermionic DM particle which is generated mainly via the freeze-out of its annihilations to the stable mediator. Since this channel is invisible, the DM indirect detection constraints should be greatly relaxed. Furthermore, the direct detection signals are suppressed to an unobservable level since fermionic DM scatterings with a nucleon appear at one-loop level. By further studying the bounds from the CMB and BBN on the visible channels involving the dark sector, we show that there is a large parameter space which can generate appropriate DM self-interactions at dwarf galaxy scales, while remaining compatible with other experimental constraints.

Multi-scalar signature of self-interacting dark matter in the NMSSM and beyond

“…There have been many solutions proposed to alleviate the tension. One class of solutions assumes different DM thermal history [15,25,57]. For example, in ref.…”

“…For example, in ref. [15], they assume the scalar mediator to be stable and annihilate into an extra scalar, constituting a subdominant DM. In the second class of solutions, the DM direct detection rate is suppressed by introducing CP-violating scalar sector [38] or inelastic DM-nucleon scattering [37], so that a large singlet scalar-SM Higgs mixing is allowed, i.e.…”

“…A viable SIDM scenario requires the DM self-scattering cross section that is suppressed at higher velocity and increases toward smaller velocity. Such feature can be implemented if the DM self-interaction is mediated by a light (O(1) MeV) scalar or vector particle [6][7][8][9][10][11][12][13][14][15][16][17].…”

Multi-scalar signature of self-interacting dark matter in the NMSSM and beyond

“…There have been many solutions proposed to alleviate the tension. One class of solutions assumes different DM thermal history [15,25,58]. For example, in Ref.…”

Maximally self-interacting dark matter: models and predictions

“…On the other hand, to explain the diversity of galactic rotation curves [13], where v ∼ 100 km/s, it is preferred to be σ/m ∼ 1 cm 2 /g [14,15]. This velocity dependence call for particle-physics model buildings: DM with a light mediator [16][17][18][19][20][21][22][23][24], DM with a resonant mediator [25,26], and composite DM [27][28][29][30][31][32][33][34]. Hereafter, we focus on an elastic scattering, while an inelastic scattering may also introduce the scale-dependence of core formation [35][36][37][38][39].…”