Number 405 (Story #1), December 7, 1998 by Phillip F. Schewe and Ben Stein|
INTRIGUING INDICATIONS OF CP VIOLATION IN B MESONS has turned up at Fermilab. CP is the abbreviation for the compound operation which turns a particle into an antiparticle (charge conjugation, or "C") and then sends the particle through a 3-dimensional looking glass (parity reflection, or "P"). A 1964 experiment unexpectedly showed that particles do not necessarily behave the same before and after the CP operation. Because CP violation is thought to account for the apparent fact that matter far outweighs antimatter in the universe physicists are eager to explore the issue further. So far CP violation only has been observed in the decay of K mesons, which contain rare s (or strange) quarks. Physicists suspect that the mysterious CP violation will also have a role in the decay of B mesons, which contain the ever rarer b (or bottom) quark. To settle this issue, B factories, dedicated electron- positron colliders that will do nothing but produce B mesons, are being built at Stanford and in Japan and elsewhere. But B mesons are already being produced in large numbers at Fermilab. The trouble here, however, is that in proton-antiproton smashups the number of B's produced is vastly outnumbered by other particles. Nevertheless, the CDF collaboration (Gerry Bauer, email@example.com, 630-840-8621) has painstakingly isolated a number of events in which B's decay into a K meson and a psi meson. The data analysis can even tell a B from an anti-B meson, and the observed asymmetry in their production is what gives a very tentative indication (based on a modest amount of data) that CP violation is occurring in B mesons. The Fermilab physicists are confident this matter can be pursued at proton machines, especially with Fermilab's much intenser beam, which will be in effect by the spring of 2000. The Stanford B factory should be running a year before that. (Abe et al, Physical Review Letters, 21 December; reporters can obtain a copy from AIP Public Information).