Measurements of direct CP violation, CPT symmetry, and other parameters in the neutral kaon system

We present a series of measurements based on K_L,S→π⁺π^- and K_L,S→π⁰π⁰ decays collected in 1996 1997 by the KTeV experiment (E832) at Fermilab. We compare these four K→ππ decay rates to measure the direct CP violation parameter Re(ɛ'/ɛ)=(20.7±2.8)×10^-4. We also test CPT symmetry by measuring the relative phase between the CP violating and CP conserving decay amplitudes for K→π⁺π^- (φ_+-) and for K→π⁰π⁰ (φ₀₀). We find the difference between the relative phases to be Δφ≡φ₀₀-φ_+- =(+0.39±0.50)°, and the deviation of φ_+- from the superweak phase to be φ_+--φ_SW=(+0.61±1.19)°; both results are consistent with CPT symmetry. In addition, we present new measurements of the K_L-K_S mass difference and K_S lifetime: Δm=(5261±15)×10⁶ ħs^-1 and τ_S=(89.65±0.07)×10^-12 s.