Present experiments at KEK 12 GeV PS

The experiments on weak interaction and the hadronic production of leptons performed at the KEK 12 GeV PS facility are described. Two weak interaction experiments and two direct electron production experiments in collisions of hadrons are introduced. One of the experiments aimed at checking the Cabibbo theory. Polarized Λ beam was produced in proton-proton collision, and the decay of Λ to pe-ν and to pμ-ν were measured. The asymmetry parameters on Λ to peν and Λ to pμν are expected to have the statistical error less than 0.01 and 0.02, respectively. Another experiment aimed at studying the existence of non-zero-Δ S neutral current and to check the gauge model of weak interaction. Low momentum kaon beam was used. The measurements of direct lepton production were carried out to study the excess yields of leptons directly produced in the proton-induced reactions. Counter experiment and bubble chamber experiment were designed. (Kato, T.)