Self-interacting dark matter through the Higgs portal

We study self-interacting dark matter coupled to the Standard Model via the Higgs portal. We consider a scenario where dark matter is a thermal relic with strong enough self-interactions that can alleviate the problems of collisionless dark matter. We study constraints from direct-detection searches, the LHC, and big bang nucleosynthesis. We show that the tension between these constraints and the need for sufficiently strong self-interactions with light mediators can be alleviated by coupling the mediator to either active or sterile neutrinos. Future direct-detection data offers great potential and can be used to find evidence of a light mediator and verify that dark matter scatters via long-range self-interactions.