Measurement of the K<sub>S</sub> content of the K° state and the branching ratio between the K<sub>S</sub>2π decays

Abstract

The K° meson state is a superposition of the short-lived and longlived states, KS and KL. The KS component decays principally to charged or neutral pion pairs. By observing the production of an ensemble of K°'s and the decay of the KS's we determined: (1) the proportion of KS in the K° state, and (2) the branching ratio between the charged and neutral two-pion decay modes of the KS. We found R(KS → π+π-)/R(KS→ π+π-) = 2.22±0.08. Within the framework of a phenomenological theory, the amount of KS overlap with the K° state is a test of CPT invariance of the weak Hamiltonian. Our results, in excellent agreement with CPT invariance, yield for the usual CPT violating parameter Re δ= - 0.0014±0.0075.