Cosmological Constraints on Invisible Decay of Dark Matter

TL;DR

This paper investigates how the decay of dark matter into neutrinos affects the universe's expansion, using supernova and CMB data to set constraints on the decay rate, finding it to be very slow over cosmic timescales.

Contribution

It provides new cosmological constraints on the decay rate of dark matter into neutrinos using observational data, which was previously less well understood.

Findings

Decay rate of dark matter into neutrinos is constrained to be very slow.

Dark matter decay has minimal impact on astrophysical processes.

Universe's expansion history can limit dark matter decay properties.

Abstract

The cold dark matter may be in a meta-stable state and decays to other particles with a very long lifetime. If the decaying products of the dark matter are weakly interacting, e.g. neutrinos, then it would have little impact on astrophysical processes and is therefore difficult to observe. However, such a decay would affect the expansion history of the Universe because of the change of the equation of state. We utilize a high-quality type Ia supernovae (SN Ia) data set selected from several resent observations and the position of the first peak of the Cosmic Microwave Background (CMB) angular spectrum given by the WMAP three-year data to constrain the dark matter decay-to-neutrino rate $\Gamma=\alpha \Gamma_{\chi}$, where $\alpha$ is the fraction of the rest mass which gets converted to neutrinos, and $\Gamma_{\chi}$ is the decay width. We find that $\Gamma^{-1} > 0.7\times10^3$ Gyr at 95.5% confidence level.