Investigation of the last flavor violation in particle physics

摘要

The flavor quantum number is not conserved in quark and neutral lepton sectors of elementary particles. This is described with the Cabbibo-Kobayashi-Maskawa (CKM) matrix in the quark sector and with the Pontecorvo-Maki- Nakagawa-Sakata (PMNS) matrix in the neutral lepton (neutrino) sector; these matrixes are recently well understood with great precision thanks to experimental efforts ongoing at particle physics laboratories. However, violation of flavor quantum number conservation in the charged lepton sector, including electron, muon and tau, is not observed yet while new physics models beyond the Standard Model predict its existence at the level just below the current experimental bounds. This indicates that exploration of flavor violation in the charged lepton sector is a clue to understand the potential of new physics. In this presentation we review current experimental efforts ongoing at high-power proton driver facilities in the world.