Testing frozen-in pNGB dark matter with a long-lived dark Higgs

TL;DR

This paper investigates a Higgs portal dark matter model where a pseudo-Nambu-Goldstone boson is produced via freeze-in, emphasizing the role of long-lived dark Higgs particles in collider and cosmological contexts.

Contribution

It introduces a novel scenario linking freeze-in dark matter production with long-lived dark Higgs phenomenology, highlighting the importance of reheating dynamics.

Findings

Dark Higgs can be long-lived and detectable at colliders.

Reheating temperature critically affects freeze-in dark matter abundance.

Collider searches for LLPs can shed light on reheating processes.

Abstract

We consider a simple Higgs portal dark matter (DM) model, where the Standard Model is extended with a complex singlet scalar. The imaginary part of the scalar becomes a massive and stable pseudo-Nambu-Goldstone boson, serving as the DM candidate, while the real part gives rise to a second (dark) Higgs boson. We focus on the freeze-in production of the DM, paying particular attention to low-reheating temperature scenarios, where the dark Higgs can be a long-lived particle (LLP). We also explore the phenomenology of this dark Higgs at the LHC and the Future Circular Collider in hadron-hadron mode, discussing its discovery prospects in regions of parameter space consistent with current DM constraints. Our results emphasize the impact of the cosmic reheating dynamics on the DM freeze-in production and their critical role in interpreting collider signatures. Furthermore, our findings suggest that LLP searches may provide insights into the fundamental dynamics of reheating.