Stau relic density at the Big-Bang nucleosynthesis era consistent with the abundance of the light element nuclei in the coannihilation scenario

TL;DR

This paper investigates the relic density of long-lived staus in the early universe within the MSSM, linking it to light element abundances during BBN to constrain model parameters.

Contribution

It provides a detailed calculation of stau relic density during BBN and establishes parameter constraints consistent with observed light element abundances.

Findings

Stau mass should be 300-400 GeV

Mass difference between stau and neutralino around 100 MeV

Stau mixing angle $ heta_\tau$ between 0.65 and 1

Abstract

We calculate the relic density of stau at the beginning of the Big-Bang Nucleosynthesis (BBN) era in the coannihilation scenario of minimal supersymmetric standard model (MSSM). In this scenario, stau can be long-lived and form bound states with nuclei. We put constraints on the parameter space of MSSM by connecting the calculation of the relic density of stau to the observation of the light elements abundance, which strongly depends on the relic density of stau. Consistency between the theoretical prediction and the observational result, both of the dark matter abundance and the light elements abundance, requires the mass difference between the lighter stau and the lightest neutralino to be around 100MeV, the stau mass to be 300 -- 400 GeV, and the mixing angle of the left and right-handed staus to be $\sin\theta_{\tau} = (0.65 \textrm{--} 1)$.