Precision Measurements in Intermediate Energy Physics

Trustees Of Boston University, Boston

Investigators

Abstract

Our research is centered on the study of the properties of subatomic particles called muons. Muons are easily produced at particle accelerators, and they are a major component of cosmic rays at the surface of the earth. According to all experimental evidence they are the same as electrons except that they are 200 times heavier, and they are 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 on its axis. It is also a magnet, with the north pole pointing along the spin axis. For a number of years, we have been doing an experiment to measure the strength of this magnet to very high precision. The value of this quantity is very sensitive to the spectrum of particles; if there are new, as yet unseen particles, then the value will be altered from theoretical expectations. We have seen a deviation from the expected value which is interesting but not yet big enough to be convincing evidence of new physics. We are proposing further measurements to sharpen the comparison between theory and experiment. At the same time, we are mounting major experiments to investigate other parameters of the muon: its lifetime, its electric dipole moment, and the probablility that it will decay directly into an electron without the usual accompanying neutrino. The last process has never been observed, and is expected to be very rare. The lifetime experiment is well under way, while the other two experiments are in development.