Precision Measurements in Intermediate Energy Physics

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Our research is centered on the study of the properties of subatomicparticles called muons. Muons are easily produced at particleaccelerators, and they are a major component of cosmic rays at thesurface of the earth. According to all experimental evidence they arethe same as electrons except that they are 200 times heavier, and theyare radioactive. It is a great mystery why muons exist at all.Like the electron, the muon can be thought of as a sphere which spins onits axis. It is also a magnet, with the north pole pointing along thespin axis. For a number of years, we have been doing an experiment tomeasure the strength of this magnet to very high precision. The valueof this quantity is very sensitive to the spectrum of particles; ifthere are new, as yet unseen particles, then the value will be alteredfrom theoretical expectations. We have seen a deviation from theexpected value which is interesting but not yet big enough to beconvincing evidence of new physics. We are proposing furthermeasurements to sharpen the comparison between theory and experiment. At the same time, we are mounting major experiments to investigate otherparameters of the muon: its lifetime, its electric dipole moment, andthe probablility that it will decay directly into an electron withoutthe usual accompanying neutrino. The last process has never beenobserved, and is expected to be very rare. The lifetime experiment iswell under way, while the other two experiments are in development.