Research
Experimental Medium-Energy Physics
CP Violation-- J. Miller, B.L. Roberts
The laws of nature are generally invariant under the symmetry operations of parity (mirror reflection), charge conjugation (matter ® antimatter), and time reversal, usually indicated by P, C, and T. However, P is violated maximally by the weak force. CP is violated at the level of 0.1% by the weak interaction, and has only been observed in the decays of neutral kaons.
Finding the source of CP violation is one of
the most important goals of particle physics. The medium-energy
group has been participating in an experiment at CERN that seeks
to measure several manifestations of CP violation in the neutral
kaon system. The technique is to study differences in partial
decay rates for initial Ko and 
beams. Many results from
this experiment are now published. Most previous experiments
instead compare KS and KL beams. Some of
these measurements will be improvements on previous experiments,
such as the measurement of D f (the difference between the p +p -
phase and the p 0p 0 phase), while others are first-time
measurements, such as the studies of CP violation in 3-
pion decays. There has been a fair amount of press surrounding
the group’s recent announcement of the first direct
measurement of T violation. The group has completed data
collection from the experiment, and analysis will continue for
several more years. The Boston University group designed and
built the time-of-flight detectors and electronics for this
experiment.
CP Violation: Schematic
diagram of the CP-Lear detector