Probing models with near degeneracy of the chargino and lightest supersymmetric particle at a lineare+e−collider

For some choices of soft supersymmetry-breaking parameters, the lighest supersymmetric particle is a stable neutralino ${\tilde{\chi }}_1^0$ that is almost degenerate in mass with the lightest chargino ${\tilde{\chi }}_1^{\pm }$ $\left(\Delta m_{\tilde{\chi }}\equiv m_{{\tilde{\chi }}_1^{\pm }}-m_{{\tilde{\chi }}_1^0}\sim m_{\pi }-\mathrm{few}\mathrm{}\mathrm{GeV}\right),$ and all other sparticles are relatively heavy. We discuss the potential of a $\sqrt{s}\sim 600\mathrm{GeV}$ $e^{+}{e}^{-}$ collider for studying such models.