  Detectors at a high-energy muon collider must be protected from the decay
products of beam muons by installing shielding material around the beam pipe.
In this article, the impact of these blind detector regions on new-physics
signatures with invisible final-state particles is shown by studying the
production of sleptons, the superpartners of leptons. Special attention is
given to large backgrounds from two-photon collisions. It is demonstrated how
the influence of these backgrounds can be controlled by implementing suitable
cuts or running at two different center-of-mass energies, thus permitting
precision measurements of the mass and spin of the sleptons. However, these
methods become ineffective for small mass differences between the sleptons and
their decay products, and it will be difficult to analyze the slepton signal at
a muon collider in this case.
