Supersymmetry at Linear Colliders: The Importance of Being e-e-
  Advantages of the e-e- option at linear colliders for the study of supersymmetry are highlighted. The fermion number violating process $e^- e^- \to \selectron^- \selectron^-$ provides unique opportunities for studies of slepton masses and flavor mixings. In particular, slepton mass measurements at the 100 MeV level through threshold scans of scalar pair production may be possible. Such measurements are over an order of magnitude better than those possible in e+e- mode, require far less integrated luminosity, and may lead to precise, model-independent measurements of $\tan\beta$. Implications for studying gauginos and the importance of accurate beam polarimetry are also discussed. 
Jonathan L. Feng (LBNL and UC Berkeley)