Search for the KS→e+e−KS→e+e− decay with the KLOE detector

We present the result of a direct search for the decay KS→e+e−KS→e+e−, obtained with a sample of e+e−→ϕ→KSKLe+e−→ϕ→KSKL events produced at DAΦNE, the Frascati ϕ-factory, for an integrated luminosity of 1.9 fb−1. The search has been performed using a pure KSKS beam tagged by the simultaneous detection of a KLKL interaction in the calorimeter. Background rejection has been optimized by using both kinematic and particle identification cuts. We find BR(KS→e+e−)<9×10−9BR(KS→e+e−)<9×10−9 at 90% CL, which improves by an order of magnitude on the previous best limit.