New Dissipation Mechanisms from Multi-level Dark Matter Scattering

TL;DR

This paper explores complex self-scattering behaviors in multi-level dark matter, revealing new dissipation mechanisms like halo cooling and drag forces driven by inelastic interactions and resonant effects.

Contribution

It introduces a comprehensive calculation of inelastic scattering cross-sections in a two-component dark matter model, highlighting novel dissipation phenomena.

Findings

Resonant enhancement of scattering due to Sommerfeld effect.

Identification of inelastic processes causing halo cooling.

Discovery of a new drag force between colliding halos.

Abstract

Multi-level dark matter with diagonal and off-diagonal interactions shows a rich phenomenology in its self-scattering. If the interactions are mediated by a particle that is less massive than the dark matter, Sommerfeld effect can lead to resonant enhancement of the scattering. For mediators lighter than the level separation, dark matter particles can upscatter to excited states and de-excite by emitting these mediators. We compute these cross-sections, both above and below the kinematic threshold, in a generic two-component dark matter model and identify the large inelastic cross-section as a result of maximal mixing between the two states. A new route for cooling of large dark matter halos and a new drag force between two colliding halos are identified and shown to arise purely from the inelastic scattering.