Can LLP detectors probe the reheating temperature? A case study of vector dark matter

TL;DR

This paper investigates how long-lived particle detectors can constrain the reheating temperature of the universe by studying a vector dark matter model with collider and cosmological implications.

Contribution

It introduces a vector dark matter model with a long-lived scalar and demonstrates how LLP searches can set bounds on the reheating temperature.

Findings

Far detectors can probe parameter space inaccessible to traditional methods.

LLP signatures from scalar decay provide new bounds on reheating temperature.

Collider and cosmological constraints complement each other in this model.

Abstract

We study an extension of the singlet-scalar Higgs portal featuring a dark vector $V_\mu$ and a real scalar $\phi$. The vector is a dark matter (DM) candidate, while $\phi$ is long-lived and decays via higher-dimensional operators. We explore the DM production via freeze-in at low and high reheating temperatures. At colliders, the decay $\phi\to Z+V$ yields distinctive long-lived particle (LLP) signatures. We explore the interplay between cosmological constraints and LLP searches at the LHC and FCC-hh, showing that far detectors can probe otherwise inaccessible parameter space and place novel bounds on the reheating temperature.