Direct Detection is testing Freeze-in

TL;DR

This paper demonstrates that current direct detection experiments can test the Freeze-in production mechanism of dark matter, especially in models involving light mediators, linking detection prospects with small-scale structure solutions.

Contribution

It is the first to show that direct detection experiments can probe Freeze-in dark matter models with light mediators, connecting detection with cosmological and astrophysical implications.

Findings

Direct detection experiments can test Freeze-in dark matter scenarios.

Light mediators enable self-interactions addressing small-scale structure problems.

FIMP candidates can have detectable signals via light mediator exchange.

Abstract

Dark Matter (DM) may belong to a hidden sector that is only feebly interacting with the Standard Model (SM) and may have never been in thermal equilibrium in the Early Universe. In this case, the observed abundance of dark matter particles could have built up through a process known as Freeze-in. We show that, for the first time, direct detection experiments are testing this DM production mechanism. This applies to scenarios where the SM and hidden sectors communicate through a light mediator particle of mass less than a few MeV. Through the exchange of such light mediator, the very same FIMP candidates can have self-interactions that are in the range required to address the small scale structure issues of collisionless cold dark matter.