Displaced new physics at colliders and the early universe before its first second

TL;DR

This paper explores how displaced vertices at colliders can reveal insights into non-standard early universe cosmology, particularly the reheating phase, through minimal freeze-in dark matter scenarios.

Contribution

It demonstrates that collider signals from long-lived particles can provide indirect constraints on the universe's reheating temperature and early history.

Findings

Displaced collider events can indicate non-standard cosmological histories.

Reheating temperature bounds can be inferred from collider signatures.

Displaced vertices are compatible with freeze-in dark matter in non-standard cosmologies.

Abstract

Displaced vertices at colliders, arising from the production and decay of long-lived particles, probe dark matter candidates produced via freeze-in. If one assumes a standard cosmological history, these decays happen inside the detector only if the dark matter is very light because of the relic density constraint. Here, we argue how displaced events could very well point to freeze-in within a non-standard early universe history. Focusing on the cosmology of inflationary reheating, we explore the interplay between the reheating temperature and collider signatures for minimal freeze-in scenarios. Observing displaced events at the LHC would allow to set an upper bound on the reheating temperature and, in general, to gather indirect information on the early history of the universe.