ELEMENTARY PARTICLES AND FIELDS Experiment Pion Program for the Future Rare-Decay Experiments *

The future investigations of rare decays of elementary particles demand the creation of new- generation setups which can perform much greater statistics and precise experimental data. The proposed new setups at CERN, NA62 (NA48/3 (P326SPS)), and at IHEP, OKA, are planned to obtain experimental data at the level of 10 −10 −10 −12 branching ratio. The main goals of both experimental programs are connected with the study of ultrarare kaon decays, but beams of these experiments contain 95% (NA48) and 50% (OKA) of pions. It is natural to use the pion part of these beams for study of rare pion decays. The pion program may be performed simultaneously or consecutively with the main tasks. Such problems as search for tensor interaction, measurements of branching ratio and form factors of some pion decays, effects of polarization, and search for new particles are included in this program.