We have measured the ratio Rsπ= Γ (KS→π+ π- (γ) ) /Γ (KS→π0 π 0) with the KLOE detector at the DAFNE e+e- collider. This measurement is fully inclusive with respect to the pi+pi-gamma final state. The sample of over 10⁶ two-pion decays of tagged Ks mesons allows a statistical error as low as 0. 1% to be obtained. The accuracy is limited by systematic uncertainties, which are estimated primarily from data. We find R=2. 236 +/- 0. 003 (stat) +/- 0. 015 (syst).
A. et al. (Mon,) studied this question.