# Detecting hidden sector dark matter at HL-LHC and HE-LHC via long-lived stau decays

## TL;DR

This paper explores the detection of hidden sector dark matter at HL-LHC and HE-LHC through the observation of long-lived stau decays into hidden sector neutralinos, which produce distinctive displaced tracks.

## Contribution

It proposes a novel method to identify hidden sector dark matter via long-lived stau decays resulting in displaced tracks at future colliders.

## Key findings

- Displaced tau tracks can signal hidden sector neutralinos.
- Simulations show detectability at HL-LHC and HE-LHC.
- Small mass gap and mixing enhance decay signatures.

## Abstract

We investigate a class of models where the supergravity model with the standard model gauge group is extended by a hidden sector $U(1)_X$ gauge group and where the lightest supersymmetric particle is the neutralino in the hidden sector. We investigate this possibility in a class of models where the stau is the lightest supersymmetric particle in the MSSM sector and the next-to-lightest supersymmetric particle of the $U(1)_X$-extended SUGRA model. In this case the stau will decay into the neutralino of the hidden sector. For the case when the mass gap between the stau and the hidden sector neutralino is small and the mixing between the $U(1)_Y$ and $U(1)_X$ is also small, the stau can decay into the hidden sector neutralino and a tau which may be reconstructed as a displaced track coming from a high $p_T$ track of the charged stau. Simulations for this possibility are carried out for HL-LHC and HE-LHC. The discovery of such a displaced track from a stau will indicate the presence of hidden sector dark matter.