A MEASUREMENT OF THE PHASES OF THE CP-VIOLATING AMPLITUDES IN K0-]2-PI DECAYS AND A TEST OF CPT INVARIANCE

The phases of the CP-violating amplitudes in K0→π+π- and K0→2π0 decays, φ+-=46.9°±2.2° and φ00=47.1°±2.8°, have been measured in the same experiment, and a direct comparison gives the phase difference φ00-φ+-=0.2°±2.9°. This result leads to an upper limit on possible CPT violation in the K0 mass matrix, of |(mK-mK)/mK|<5×10-18 at the 95% confidence level and is the most stringent test of the equality of particle and antiparticle masses. © 1990.