Recent results from NA48/2 experiment

The first observation of about 2000 candidates, with a background contamination below 3%, of the rare decay K± → π±π0e−e+ is reported. The preliminary branching ratio in the full kinematic region is obtained to be: BR(K± → π±π0e−e+)= (4.06±0.17).106 by analyzing the data collected in 2003. A sample of 1.69×107 π0 → e−e+γ decay candidates with a negligible background contamination collected in 2003–2004 data is analyzed to search for the dark photon (A′) production in the π0 → γA′ decay followed by the prompt A′ → e−e+ decay. No signal is observed, and exclusion region in the plane of the dark photon mass (mA′ ) and mixing parameter ε2 is established.