# Long life stau in the minimal supersymmetric standard model

## TL;DR

This paper investigates the lifetime of the stau in the minimal supersymmetric standard model, focusing on scenarios with a neutralino LSP and a nearly degenerate stau NLSP, covering a vast range of possible lifetimes.

## Contribution

It provides detailed calculations of the stau lifetime considering various decay modes and explores the impact of slepton mixing on lepton flavor violation.

## Key findings

- Stau lifetime varies from 10^{-22} to 10^{16} seconds.
- Lifetime depends on the mass difference between stau and neutralino.
- Potential implications for lepton flavor violation are discussed.

## Abstract

We study the stau lifetime in a scenario with the LSP taken to be a neutralino and the NLSP being a stau, based on the minimal supersymmetric Standard Model. The mass difference between the LSP and NLSP, $\delta m$, must satisfy $\delta m/m_{\tilde{\chi}} \sim$ a few % or less for coannihilation to occur, where $m_{\tilde{\chi}}$ is the neutralino mass. We calculate the stau lifetime from the decay modes $\tilde{\tau}\to \tilde{\chi}\tau$, $\tilde{\chi}\nu_\tau\pi$, and $\tilde{\chi}\nu_\tau\mu(e)\nu_{\mu(e)}$ and discuss its dependence on various parameters. We find that the lifetime is in the range $10^{-22}$--$10^{16}$ sec for $10^{-2} \le \delta m \le 10$ GeV. We also discuss the connection with lepton flavor violation if there is mixing between sleptons.