Fermilab's Intensity Frontier

Particle physics experiments at the intensity frontier aim to probe nature through precision studies of the properties and interactions of its basic constituents, using intense particle beams and innovative detectors. We review the physics potential of several of these experiments, especially those that can be very effectively pursued at Fermilab in the near and intermediate future, assuming that a new intense proton source Project X will be available. We concentrate on flavor-violating phenomena that have been identified as the main particle physics drivers for Project X: the study of neutrino masses and mixing through long-baseline neutrino oscillations; searches for rare, flavor-violating muon processes; and precision measurements of kaon decays into neutrinos, K -> pi nu(nu) over bar. We also comment on other opportunities, such as measurements of the anomalous magnetic moment of muon and neutrino-matter scattering.