Strong Dark Matter Self-Interaction from a Stable Scalar Mediator

Understand

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.