Approach to new physics through kaon rare decay study

We are searching for a CP-violating rare decay of the neutral kaon: K_L⁰ → π⁰νν-bar at the Japan Proton Accelerator Research Complex (J-PARC) to explore new physics beyond the Standard Model in the particle physics. Based on the data taken in 2015, we set an upper limit on the branching ratio of 3x10^-9 at the 90% confidence level; improving the current world record by an order of magnitude. This is just the first step of our quest for new physics beyond the Standard Model. We will continue exploring uncharted territory by increasing the beam intensity, and by upgrading our detector based on the knowledge obtained at each sensitivity level. (author)