Right after the Big Bang, the same number of particles and antiparticles were produced, but as the universe cooled down, they annihilated each other and disappeared. However, there is matter made of particles, such as stars, left in the universe. This was caused by a small difference between particles and antiparticles, called CP violation. Although the CP violation was observed in laboratories and explained in the Standard Model by Kobayashi and Maskawa, the mechanism of the CP violation that created the matter in the universe is still a mystery. At the new J-PARC high intensity proton accelerator facility, we are studying a rare KL decay mode to look for a new source of CP-violation caused by physics beyond the Standard Model.
In addition, right after the Big Bang, all the particles were massless, but later, they obtained mass due to a hypothetical particle, the Higgs boson. Using the world,s highest energy proton-proton collider at CERN, we are searching for the Higgs boson. The same collider will allow us to produce undiscovered particles predicted by Supersymmetry which is the most popular theory beyond the Standard Model. Supersymmetry is a symmetry relating fermionic and bosonic degrees of freedom. It is the only theory that could unify gravity and the other three forces. We are also searching for such supersymmetric particles.
The KL experiment at the J-PARC.
The ATLAS experiment at the LHC at CERN.