A measurement of the phases of the CP-violating amplitudes in K0→2π decays and a test of CPT invariance

Abstract The phases of the CP -violating amplitudes in K 0 → π + π − and K 0 →2 π 0 decays, φ +− =46.9°±2.2° and φ 00 =47.1°±2.8°, have been measured in the same experiment, and a direct comparison gives the phase difference φ 00 − φ +− =0.2°±2.9°. This result leads to an upper limit on possible CPT violation in the K 0 mass matrix, of |(m K 0 −m K 0 )/m K 0 | −18 at the 95% confidence level and is the most stringent test of the equality of particle and antiparticle masses.