Prethermalization Production of Dark Matter

TL;DR

This paper investigates how dark matter can be produced during the prethermal phase after inflation, showing that the production mechanism depends on the energy dependence of the cross section and the scale of supersymmetry.

Contribution

It analyzes the role of prethermalization in dark matter production, highlighting the dependence on the cross section's energy scaling and supersymmetry scale.

Findings

Prethermal phase can dominate dark matter production for certain cross sections.

Entropy production during reheating suppresses nonthermal contributions for some models.

Nonthermal production is significant in high-scale supersymmetry models.

Abstract

At the end of inflation, the inflaton field decays into an initially nonthermal population of relativistic particles which eventually thermalize. We consider the production of dark matter from this relativistic plasma, focusing on the prethermal phase. We find that for a production cross section $\sigma(E)\sim E^n$ with $n> 2$, the present dark matter abundance is produced during the prethermal phase of its progenitors. For $n\le 2$, entropy production during reheating makes the nonthermal contribution to the present dark matter abundance subdominant compared to that produced thermally. As specific examples, we verify that the nonthermal contribution is irrelevant for gravitino production in low scale supersymmetric models ($n=0$) and is dominant for gravitino production in high scale supersymmetry models ($n=6$).