CP Violation in the Decay of B Mesons

CP violation in the decay of B mesons has now definitively been observed at SLAC. CP is an abstract abbreviation for a mathematical operation in which particles undergo a change in charge conjugation (C) and parity (P). The combined CP operation essentially turns a particle into an antiparticle.

To say that CP symmetry is violated is to say that the physical properties of particles and antiparticles are not fully the same, a fact discovered first almost 40 years ago in the decay of K mesons. Since then B factories at SLAC and the Japanese KEK lab, where colliding electrons and positrons produce copious amounts of B mesons, have zeroed in on producing the same result with the rarer B mesons.

Both groups submitted preliminary results in February of this year (Update 525) with very limited data sets. Now SLAC is offering a more robust measurement of the CP-violating parameter, referred to as sine (2beta); the value it reports is 0.59 with an uncertainty of 0.14. (SLAC press release, 6 July 2001 and paper submitted to Physical Review Letters.)