Number 44 (Story #3), August 8, 1991 by Phillip F. Schewe and Ben Stein STUDYING CP VIOLATION , with the help of accelerators devoted to the production of B mesons, is the best way to probe the standard model of particle physics, according to Cornell physicist Karl Berkelman (607-255-4198). At least until the SSC is built. Experiments have provided indirect evidence that certain decay modes of the B violate CP invariance; that is, the rate for these decays is slightly different for particles and antiparticles. Present accelerators, however, cannot produce enough of the short-lived B's to test for CP violation. Dedicated B factories (construction proposals for Cornell and Stanford and other labs around the world are now pending) would produce sufficient numbers of B's by colliding electron beams and positron beams at slightly different energies. The asymmetric beams would allow the B's to be produced not at rest but with a great forward velocity, a property which (by the laws of special relativity) extends their lifetime (and therefore their detectability) in the lab frame of reference. (Mosaic, Summer 1991.)