The Four Basic Ways of Creating Dark Matter Through a Portal

TL;DR

This paper explores four fundamental mechanisms by which dark matter could have been produced via portals connecting it to the Standard Model, analyzing their relic densities and experimental testability.

Contribution

It introduces a unified phase diagram for dark matter production mechanisms through two portals and highlights the experimental prospects for probing these scenarios.

Findings

Four distinct dark matter production regimes identified.

Relic density shapes form a 'Mesa' in the phase diagram.

Kinetic mixing portal scenarios are testable by upcoming experiments.

Abstract

We consider the possibility that along the thermal history of the Universe, dark matter (DM) would have been created from Standard Model particles, either through a kinetic mixing portal to an extra U(1) gauge field, or through the Higgs portal. Depending solely on the DM particle mass, on the portal and on the DM hidden sector interaction, we show how the observed DM relic density can be obtained. There are four possible freeze-in/reannihilation/freeze-out regimes, which together result in a simple characteristic relic density phase diagram, with the shape of a "Mesa". In the case of the kinetic mixing portal, we show that, unlike other freeze-in scenarios discussed in the literature, the freeze-in regime can be probed by forthcoming DM direct detection experiments. These results are well representative {of} any scenario where a DM hidden sector would be created out of the Standard Model {sector}.