Cosmological Constraints on Long-Lived Particles Using Dimension-Six Effective Operators

TL;DR

This paper explores how long-lived particles decaying into dark matter affect early universe processes, using effective operators to constrain their properties based on cosmological observations.

Contribution

It introduces a framework using dimension-six effective operators to analyze cosmological constraints on LLP decays into dark matter.

Findings

LLP decays can disrupt Big Bang Nucleosynthesis if lifetime exceeds 10^4 seconds.

Decays contribute to effective neutrino species, affecting cosmological parameters.

Parameter space is constrained by BBN, CMB, structure formation, and BAO data.

Abstract

Long-lived particles (LLPs) provide an interesting window into physics beyond the Standard Model, offering characteristic signatures at colliders and in cosmology. In this work, we investigate LLPs decays into dark matter. If the lifetime of LLPs are longer than $10^4$s, the decay products can disrupt the synthesis of light nuclei in the early universe and alter Big Bang Nucleosynthesis (BBN) predictions. If the LLP is much heavier than the dark matter particle, the decay contributes to the number of effective neutrino species, $N_{eff}$. We describe these decays via dimension-six effective operators and outline the parameter space in which such decays obey cosmological bounds stemming from BBN, structure formation, Cosmic Microwave Background, and Baryon Acoustic Oscillation data.