Confronting Dark Matter Freeze-In during Reheating with Constraints from Inflation

TL;DR

This paper examines how non-instantaneous reheating after inflation affects dark matter production via freeze-in, influencing particle decay predictions and collider search constraints.

Contribution

It introduces a detailed analysis of reheating dynamics' impact on dark matter freeze-in, emphasizing the importance of inflation models and accurate reheating temperature definitions.

Findings

Reheating dynamics significantly alter dark matter production predictions.

Decay lengths of parent particles are larger with non-instantaneous reheating.

LLP searches can probe inflationary reheating scenarios.

Abstract

We investigate the production of particle Dark Matter (DM) in a minimal freeze-in model considering a non-instantaneous reheating phase after inflation. We demonstrate that for low reheating temperatures, bosonic or fermionic reheating from monomial potentials can lead to a different evolution in the DM production and hence to distinct predictions for the parent particle lifetime and mass, constrained by long-lived particle (LLP) searches. We highlight that such scenario predicts parent particle decay lengths larger compared to using the instantaneous reheating approximation. Moreover, we demonstrate the importance of an accurate definition of the reheating temperature and emphasize its relevance for the correct interpretation of experimental constraints. We explore different models of inflation, which can lead to the considered reheating potential. We find that the extent to which the standard DM freeze-in production can be modified crucially depends on the underlying inflationary model. Based on the latest CMB constraints, we derive lower limits on the decay length of the parent particle and confront these results with the corresponding reach of LLP searches. Our findings underscore the impact of the specific dynamics of inflation on DM freeze-in production and highlight their importance for the interpretation of collider signatures. At the same time, our results indicate the potential for LLP searches to shed light on the underlying dynamics of reheating.