Warm dark matter from freeze-in at stronger coupling

TL;DR

This paper explores warm dark matter produced via freeze-in with strong Higgs coupling, highlighting collider detection prospects and the impact of Lyman-alpha bounds on low-mass dark matter.

Contribution

It introduces a scenario where low-temperature conditions allow strong Higgs coupling, leading to detectable warm dark matter with a non-thermal momentum distribution.

Findings

Lyman-alpha bounds exclude dark matter masses below 50-100 keV.

Dark matter has a highly non-thermal momentum distribution with a low-momentum cutoff.

Strong Higgs coupling enables collider detection of warm dark matter.

Abstract

We study warm Higgs portal dark matter (DM) in the framework of freeze-in at stronger coupling. This scenario assumes that the Standard Model thermal bath temperature has always been relatively low, which suppresses dark matter production. As a result, a significant DM-Higgs coupling is allowed, enabling warm dark matter detection via Higgs decay at colliders. We find that the Lyman-{\alpha} bound on the DM mass is particularly strong, excluding masses below 50-100 keV, depending on further details. The shape of the DM momentum distribution is highly non-thermal, with low momenta being effectively cut off, and not captured by the common {\alpha}{\beta}{\gamma}-parametrization.