B Factories

Search for new physics at KEK B-factory: Belle experiment

One of the major research activities in our group has been a study of CP-violation and a search for physics beyond the Standard Model in the B meson and the τ lepton systems using the KEK B-factory (KEKB).
Our group played a central role in the discovery of CP violation in the B meson system in 2001, which proved the theory proposed by Kobayashi and Maskawa, who were awarded Nobel Prize in Physics in 2008.

We have been studying of Michel parameters of the τ lepton, which is sensitive to physics beyond the Standard Model. Using ∼ 900 million τ+τ− pairs recorded with the Belle detector, we intend to significantly improve the precision of measurement over previous measurements. We are also studying an improved measurement of the CP violating parameter, φ3, which is currently the least well-measured of the three CKM angles

Physics at luminosity frontier: Belle II experiment

The SuperKEKB project started in 2010. The upgraded accelerator, SuperKEKB, will have a 40 times more luminosity than KEKB. The Belle detector is also being upgraded as the “Belle II” detector with cutting-edge technologies. One of the key elements for the success of Belle II will be its Silicon Vertex Detector (SVD) to precisely measure the decay points of B mesons. Our group is responsible for the construction of the outermost layer of the Belle II SVD. In addition, we have been developing the track finder software with SVD for long-lived particles, such as KS. The R&D for the upgrade of the Belle II electromagnetic calorimeter has been also carried out.