PHASE DIFFERENCE BETWEEN KL-]PI+PI- AND KS-]PI+PI- DECAY AMPLITUDES

The phase difference between the KL → π+π- and KS → π+π- decay amplitudes has been measured by observing the time dependence of the π+π- decay intensity from an initial K° (strangeness = +1) state. The phase difference φ/+- is found to be 41° ± 12° for a KL - KS mass difference Δm/ h {combining short stroke overlay} = 0.526 × 1010 sec-. The error includes statistical and systematic uncertainties. The phase φ+- is strongly correlated to the value adopted for Δm/ h {combining short stroke overlay}. The present uncertainty on Δm/ h {combining short stroke overlay} increases our error on φ+- from 12° to 15°. The result is in agreement with the prediction of the 'superweak model' of CP violation. © 1969.