Long life stau in the minimal supersymmetric standard model

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.

Comments: 15 pages, 5 figures