Sparticle Masses from Kinematic Fitting at a Muon Collider
  Three case studies are presented of slepton pair production followed by two-body or quasi-two-body decays at a muon collider. Precision mass measurements are possible using a variety of kinematic fitting methods. Standard Model and supersymmetric backgrounds are easily controlled by kinematic cuts. In all three cases it appears that detector resolutions, not backgrounds or statistics, will dominate the final error bars. Polarized beams are not necessary to control SM backgrounds. However, without polarization it may be difficult in some cases to disentangle slepton_right from slepton_left signals. 
Joseph D. Lykken