Ultraviolet Freeze-in with a Time-dependent Inflaton Decay

TL;DR

This paper investigates how a time-dependent inflaton decay rate during reheating affects ultraviolet freeze-in dark matter production, highlighting differences from constant decay assumptions and providing specific production scenarios.

Contribution

It introduces the impact of a time-dependent inflaton decay width on UV freeze-in dark matter genesis, contrasting with traditional constant decay models.

Findings

Time-dependent decay width significantly alters DM yield.

UV freeze-in can occur during reheating with high-dimension operators.

Concrete examples show varied DM production mechanisms.

Abstract

It is typically assumed that during reheating the inflaton decays with a constant decay width. However, this is not guaranteed and can have a strong impact on the dark matter (DM) genesis. In the context of the ultraviolet (UV) freeze-in mechanism, if the operators connecting the dark and visible sectors are of sufficiently high mass dimension, the bulk of the DM abundance is produced during and not after reheating. We study here the impact of a time-dependent decay width of the inflaton on the DM abundance, emphasizing the differences with respect to the cases where the decay is either instantaneous or constant. We also provide concrete examples for DM production via UV freeze-in, e.g., from 2-to-2 scatterings of standard model particles, or from inflaton scatterings or decays, elucidating how the time-dependence influences the DM yield.