Title：(g−2)_{mu} Versus Flavor Changing Neutral Current Induced by the Light (B−L)_{mu tau} Boson

Speaker：Dr. Yoshihiro Shigekami , Huazhong University of Science and Technology

Time:October 28, 2019 ,15:00 PM

Venue：333 Lecture Hall, Physics Building

Abstract：

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 of O(10) MeV to account for the discrepancy of the muon anomalous magnetic moment. However, 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 cannot naturally suppress the FCNC from the down-type quark sector and thus requires a large fine-tuning to avoid the stringent K --> pi nu nubar bound. 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 is O(10^−4).