  The physics potential of an intense source of low-energy muons is studied.
Such a source is a necessary stage towards building the neutrino factories and
muon colliders which are being considered at present. The CERN Neutrino Factory
could deliver muon beams with intensities 3-4 orders of magnitude higher than
available now, with large freedom in the choice of the time structure.
Low-energy muon physics contributes to many fields of basic research, including
rare muon decays, i.e., decays that do not conserve muon number, measurements
of fundamental constants, the muon anomalous magnetic moment, determination of
the Lorentz structure of the weak interaction, QED tests, CPT tests, proton and
nuclear charge distributions (even for short-lived isotopes), and condensed
matter physics. In studying the experimental programme, we analyse the present
limitations, list the requirements on the new muon beams, and describe some
ideas on how to implement these beam lines in a CERN neutrino factory complex.
