Precision measurement of the ratio BR(K-S -> pi(+)pi(-)e(+)e(-))/BR(K-L -> pi(+)pi(-)pi(0)(D))

The K-S -> pi(+)pi(-)e(+)e(-) decay mode was investigated using the data collected in 2002 by the NA48/1 Collaboration. With about 23 k K-S -> pi(+)pi(-)e(+)e(-) events and 59 k K-L -> pi(+)pi(-)pi(0)(D) normalization decays, the K-S -> pi(+)pi(-)e(+)e(-) branching ratio relative to the K-L -> pi(+)pi(-)pi(0)(D) one was determined to be BR(K-S -> pi(+)pi(-)e(+)e(-))/BR(K-L -> pi(+)pi(-)pi(0)(D)) = (3.28 +/- 0.06(stat) +/- 0.04(syst)) x 10(-2). This result was used to set the upper limit vertical bar g(E1)/g(BR)vertical bar < 3.0 at 90% CL on the presence, in the decay amplitude, of an E1 direct emission (g(E1)) term relative to the dominant inner bremsstrahlung (g(BR)) term. The CP-violating asymmetry A(phi) in the sin phi cos phi distribution of K-S -> pi(+)pi(-)e(+)e(-) events, where phi is the angle between the pi(+)pi(-) and the e(+)e(-) decay planes in the kaon centre of mass, was found to be A(phi) = (-0.4 +/- 0.8)%, consistent with zero. These results are in good agreement with a description of the K-S -> pi(+)pi(-)e(+)e(-) decay amplitude dominated by the CF-even inner bremsstrahlung process.