Full-shape BOSS constraints on dark matter interacting with dark radiation and lifting the $S_8$ tension

TL;DR

This paper uses full-shape galaxy clustering data combined with CMB and BAO measurements to constrain models of dark matter interacting with dark radiation, aiming to reduce the $S_8$ tension and explore underlying particle physics.

Contribution

It provides new constraints on ETHOS models of dark matter-dark radiation interactions, linking cosmological data with particle physics models like non-Abelian gauge interactions.

Findings

Reduced $S_8$ tension to about 1 sigma with specific dark sector parameters.

Derived lower bounds on dark gauge coupling strength compatible with structure formation.

Identified temperature-dependent interaction scenarios consistent with observational bounds.

Abstract

In this work we derive constraints on interacting dark matter-dark radiation models from a full-shape analysis of BOSS-DR12 galaxy clustering data, combined with Planck legacy cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) measurements. We consider a set of models parameterized within the effective theory of structure formation (ETHOS), quantifying the lifting of the $S_8$ tension in view of KiDS weak-lensing results. The most favorable scenarios point to a fraction $f\sim 10-100\%$ of interacting dark matter as well as a dark radiation temperature that is smaller by a factor $\xi\sim 0.1-0.15$ compared to the CMB, leading to a reduction of the tension to the $\sim 1\sigma$ level. The temperature dependence of the interaction rate favored by relaxing the $S_8$ tension is realized for a weakly coupled unbroken non-Abelian $SU(N)$ gauge interaction in the dark sector. To map our results onto this $SU(N)$ model, we compute higher-order corrections due to Debye screening. We find a lower bound $\alpha_d\equiv g_d^2/(4\pi)\gtrsim 10^{-8} (10^{-9})$ for dark matter mass $1000 (1)$ GeV for relaxing the $S_8$ tension, consistent with upper bounds from galaxy ellipticities and compatible with self-interactions relevant for small-scale structure formation.