Dark Matter Dilution Mechanism through the Lens of Large Scale Structure

TL;DR

This paper investigates how the decay of a long-lived particle affects dark matter abundance and the primordial matter power spectrum, using large scale structure data to constrain models with dark matter dilution mechanisms.

Contribution

It derives the first stringent limit on the decay branching ratio to dark matter from large scale structure observations, providing a new test for dark matter dilution models.

Findings

Stringent limit on dilutor's branching ratio to dark matter from SDSS data.

Excludes large parameter space for right-handed neutrino warm dark matter.

Demonstrates the impact of decay processes on primordial matter power spectrum.

Abstract

Entropy production is a necessary ingredient for addressing the over-population of thermal relics. It is widely employed in particle physics models for explaining the origin of dark matter. A long-lived particle that decays to the known particles, while dominating the universe, plays the role of the dilutor. We point out the impact of its partial decay to dark matter on the primordial matter power spectrum. For the first time, we derive a stringent limit on the branching ratio of the dilutor to dark matter from large scale structure observation using the SDSS data. This offers a novel tool for testing models with a dark matter dilution mechanism. We apply it to the left-right symmetric model and show that it firmly excludes a large portion of parameter space for right-handed neutrino warm dark matter.