Finite Temperature NLO Corrections in Relativistic Scatterings: Implications for Dark Matter Freeze-In

TL;DR

This paper calculates NLO thermal corrections to relativistic scatterings in the early Universe, showing they can significantly alter dark matter abundance predictions by up to 30%.

Contribution

It provides the first detailed analysis of finite temperature NLO effects on scalar dark matter freeze-in production.

Findings

NLO corrections can change dark matter yield by approximately 30%.

Thermal mass corrections alone overestimate the reduction in scattering rates.

Finite temperature NLO effects can modify the relic abundance by around 10%.

Abstract

We study the next-to-leading order (NLO) virtual and thermal corrections to relativistic $2 \rightarrow 2$ scattering processes involving scalar particles in the early Universe thermal plasma. Taking the example of freeze-in production of scalar dark matter pairs through these scatterings, we evaluate the impact of the NLO corrections to the annihilation rate and the dark matter yield. We find that including only thermal mass corrections to a leading order interaction rate can overestimate the reduction in these rates, and the full NLO corrections can modify the DM abundance predictions by $\mathcal{O}(30\%)$. It is also observed that while the virtual NLO effects are larger, the finite temperature NLO corrections to the matrix elements in the relativistic regime can modify the DM abundance by $\mathcal{O}(10\%)$, in comparison to the virtual NLO corrections.