  Most supersymmetric models predict new particles within the reach of the next
generation of colliders. For an understanding of the model structure and the
mechanism(s) of electroweak symmetry breaking, it is important to know the
masses of the new particles precisely. The measurement of the mass of the
scalar partner of the top quark (stop) at an e+e- collider is studied. A
relatively light stop is motivated by attempts to explain electroweak
baryogenesis and can play an important role in dark matter annihilation. A
method is presented which makes use of cross-section measurements near the
pair-production threshold as well as at higher center-of-mass energies. It is
shown that this method does not only increase the statistical precision, but
also reduces the influence of systematic uncertainties, which can be important.
Numerical results are presented, based on a realistic event simulation, for two
signal selection strategies: using conventional selection cuts, and using an
Iterative Discriminant Analysis (IDA). While the analysis of stops is
particularly challenging due to the possibility of stop hadronization and
fragmentation, the general procedure could be applied to many precision mass
measurements.
