Freezing-in Cannibals with Low-reheating Temperature

TL;DR

This paper explores how a non-instantaneous reheating phase and dark sector self-interactions, especially cannibalization processes, influence the freeze-in production of dark matter, revealing new phenomenological possibilities.

Contribution

It introduces a detailed numerical analysis of dark matter freeze-in considering prolonged reheating and cannibalistic self-interactions, highlighting their impact on dark matter abundance and thermal history.

Findings

Reveals significant effects of non-instantaneous reheating on dark matter production.

Demonstrates the role of self-interactions in modifying dark sector thermalization.

Identifies new parameter space for light dark matter detection.

Abstract

The freeze-in mechanism provides a compelling framework for dark matter (DM) production, particularly suited to scenarios involving feeble interactions with the Standard Model (SM). In this work, we highlight a possible interplay of a non-instantaneous reheating phase and dark sector self-interactions, specifically $2 \to 3$ and $3 \to 2$ cannibalization processes. As an example we study the freeze-in production of a complex scalar DM candidate stabilized by a $\mathbb{Z}_3$ symmetry permitting cubic self-couplings, enabling number-changing interactions that drive internal thermalization and significantly modify the dark sector number density and temperature evolution. We numerically solve the coupled Boltzmann equations for the DM number density and temperature alongside the evolving SM bath, accurately capturing the dynamics of a prolonged reheating epoch. Our analysis reveals a rich and distinctive phenomenology arising from the interplay between the Universe's thermal history, Higgs portal mediated production, and cannibalistic self-interactions. Compared to scenarios with instantaneous reheating or negligible self-interactions, our framework opens new viable regions in parameter space, particularly for light DM, potentially within reach of future probes.