Department of Physics, Graduate School of Science
My major is high energy physics (particle physics experiment). In particular, I work on the KOTO experiment at J-PARC to search for the rare neutral kaon decay called 
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The Standard Model of elementary particles explains almost all the behavior of the particles, however, it leaves some mysteries unexplainable. One of them is the origin of the matter-dominated universe. At the very beginning of the universe, there should have been equal amounts of matter and antimatter though the current universe is made of matter. This stems from violation of the symmetry between particle and antiparticle (CP symmetry). The Standard Model gives an explanation about the CP violation. However, it is not enough to explain the matter-dominated universe. Thus, there should be physics beyond the Standard Model which violates CP symmetry.
According to the Standard Model, the decay breaks CP symmetry and its branching ratio is predicted to be 3 × 10－11, which is quite small. In addition, theoretical uncertainty of it is also small, therefore, if there is a discrepancy between the measured value and the predicted value, it immediately implies the existence of new physics. For these reasons, we are trying to observe the decay, which has yet to be discovered.