The short distance behavior of dark matter (DM) at galaxy scales exhibits several features not explained by the typical cold dark matter with velocity-independent cross section. We discuss a particle physics model with a hidden sector interacting feebly with the visible sector where a dark fermion self-interacts via a dark force with a light dark photon as the mediator. We study coupled Boltzmann equations involving two temperatures, one for each sector. We fit the velocity-dependent DM cross section to the data from scales of dwarf galaxies to clusters consistent with relic density constraint.

• Received 2 August 2020
• Revised 12 January 2021
• Accepted 17 March 2021

DOI:https://doi.org/10.1103/PhysRevD.103.075014

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Published by the American Physical Society