Upper limit for the branching ratio of K{sub S}{yields}e{sup +}e{sup -} decay

A measurement of the branching ratio for K{sub S}{yields}e{sup +}e{sup -} decay was performed with the CPLEAR detector at LEAR. Full event reconstruction together with calorimeter e/{pi} separation allowed for powerful background rejection and high signal acceptance. The analysis on the complete set of data yields the result: BR(K{sub S}{yields}e{sup +}e{sup -})<1.4{center_dot}10{sup -7} (90% CL), an improvement on the current experimental limit by a factor of 20.