# Dark matter seeping through dynamic gauge kinetic mixing

## TL;DR

This paper demonstrates that loop-induced kinetic mixing between visible and dark gauge bosons can enable dark matter production via a temperature-dependent portal, with suppression from heavy fermion masses, primarily during early reheating.

## Contribution

It introduces a novel 'dynamic' portal mechanism for dark matter production through loop-driven kinetic mixing, emphasizing temperature sensitivity and suppression factors.

## Key findings

- Dark matter can be produced via a temperature-dependent kinetic mixing portal.
- Loop-driven kinetic mixing can facilitate freeze-in dark matter production.
- The suppression from heavy fermions justifies the small portal interaction strength.

## Abstract

We show for the first time that the loop-driven kinetic mixing between visible and dark Abelian gauge bosons can facilitate dark matter production in the early Universe by creating a 'dynamic' portal, which depends on the energy of the process. The required smallness of the strength of the portal interaction, suited for freeze-in, is justified by a suppression arising from the mass of a heavy vector-like fermion. The strong temperature sensitivity associated with the interaction is responsible for most of the dark matter production during the early stages of reheating.