Signatures of Self-Interacting Dark Matter in the Matter Power Spectrum and the CMB

TL;DR

This paper explores a self-interacting dark matter model with a decaying dark photon, revealing implications for the matter power spectrum and CMB, and suggesting future observational prospects for dark sector properties.

Contribution

It introduces a novel dark matter model with dark photon decay, connecting galactic halo observations to early universe asymmetries and cosmological signatures.

Findings

Dark matter produced asymmetrically in the early universe.

Presence of dark radiation and late kinetic decoupling.

Strong constraints from Lyman-alpha forest measurements.

Abstract

We consider a self-interacting dark matter model in which the massive dark photon mediating the self-interaction decays to light dark fermions to avoid over-closing the universe. We find that if the model is constrained to explain the dark matter halos inferred for spiral galaxies and galaxy clusters simultaneously, there is a strong indication that dark matter is produced asymmetrically in the early universe. It also implies the presence of dark radiation, late kinetic decoupling for dark matter, and a suppressed linear power spectrum due to dark acoustic damping. The Lyman-$\alpha$ forest power spectrum measurements put a strong upper limit on the damping scale and the model has little room to reduce the abundances of satellite galaxies. Future observations in the matter power spectrum and the CMB, in tandem with the impact of self-interactions in galactic halos, makes it possible to measure the gauge coupling and masses of the dark sector particles even when signals in conventional dark matter searches are absent.