Measurement of Gamma(K-S ->pi(+)pi(-)(gamma))/Gamma(K-S ->pi(0)pi(0))

We have measured the ratio R-S(pi) = Gamma(K-S --> pi(+)pi(-)(gamma))/Gamma(K-S --> pi(0)pi(0)) with the KLOE detector at the DAPhiNE 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 K-S mesons allows a statistical error as low as similar to 0.1% to be obtained. The accuracy is limited by systematic uncertainties, which are estimated primarily from data. We find R-S(pi) = 2.236 +/- 0.003(stat) +/- 0.015(syst). (C) 2002 Elsevier Science B.V. All rights reserved.