FIRST OBSERVATION OF K_S→π⁰e⁺e^- AND K_S→π⁰μ⁺μ^- AT NA48/1

Using data taken on 2002 at the CERN SPS accelerator, the NA48/1 collaboration has made the first observation of the rare decays K_S→π⁰e⁺e^- and K_S→π⁰μ⁺μ^-. Seven events were found in the electron channel with an estimated background of . For the muon channel 6 events were observed with a background of . Using vector a matrix element with unity form factor the resulting branching ratios are: and .