A new determination of the Ko --> π+π- decay parameters

In a short neutral beam we have measured the proper time-dependence of the decay K^o --> π⁺π^-. This time structure exhibits the interference between the short- and long-lived states and is in agreement with the general expectations of the CP violation phenomenology.

This experiment gives new and more precise measurements of the following three parameters:

i) the decay width of the short-lived K_S component: Γ_S = (1.119+/-0.006) × 10¹⁰ sec^-1

ii) the modulus of the CP violating parameter η_+-: |η_+-| = (2.30+/-0.035) × 10^-3

iii) the phase of η_+- as a function of the K_S-K_L mass difference Δm:φ_+- = (49.4+/-1.0)^o + [(Δm-0.540)/0.540] × 305^o

The result of |η_+-| may be compared with the result of the foregoing letter on Re ɛ in the frame of the superweak model. Good agreement is observed.

Now at Gesamthochschule, Siegen, Germany.