General Constraints on Dark Matter Decay from the Cosmic Microwave Background

TL;DR

This paper introduces a principal component analysis method to efficiently constrain dark matter decay models using cosmic microwave background data, enabling model-independent bounds on various decay scenarios.

Contribution

It develops a simple, model-dependent detectability factor for dark matter decay effects on the CMB, validated with Planck data and MCMC methods.

Findings

Set bounds on dark matter decay lifetimes shorter than the universe's age.

Demonstrated a single-parameter characterization of decay effects.

Validated the approach with Planck 2015 data.

Abstract

Precise measurements of the temperature and polarization anisotropies of the cosmic microwave background can be used to constrain the annihilation and decay of dark matter. In this work, we demonstrate via principal component analysis that the imprint of dark matter decay on the cosmic microwave background can be approximately parameterized by a single number for any given dark matter model. We develop a simple prescription for computing this model-dependent detectability factor, and demonstrate how this approach can be used to set model-independent bounds on a large class of decaying dark matter scenarios. We repeat our analysis for decay lifetimes shorter than the age of the universe, allowing us to set constraints on metastable species other than the dark matter decaying at early times, and decays that only liberate a tiny fraction of the dark matter mass energy. We set precise bounds and validate our principal component analysis using a Markov Chain Monte Carlo approach and Planck 2015 data.