SEMINAR

Yoshihiro Shigekami (Huazhong University of Science and Technology, China)

We propose the local (B-L)_{mu tau} model, which minimally retains the
local B-L extension for the sake of neutrino phenomenologies, and at
the same time presents an invisible gauge boson Z' with mass O(10)
MeV to account for the discrepancy of the muon anomalous magnetic
moment. But such a scenario is challenged by flavor physics. To
accommodate the correct pattern of Cabibbo-Kobayashi-Maskawa
matrix, we have to introduce either a SU(2)_L doublet flavon or
vector-like quarks plus a singlet flavon. In either case Z' induces flavor
changing neutral current (FCNC) in the quark sector at tree-level. We
find that the former scheme is completely ruled out by K → pi nu nu.
Whereas the latter scheme, in which FCNC merely arises in the up-type
quark sector, is still free of strong constraint. In particular, it opens a new
window to test our scenario by searching for flavor-changing top quark
decay mode t → u/c+(invisible), and the typical branching ratio O(10^{-4}).

5月31日（金）10:45 ～ 12:15 近畿大学東大阪キャンパス 31号館, 501教室