Particle physics and phenomenology

1. Gauged Two Higgs Doublet Model. We constructed a gauged 2HDM (G2HDM) by embedding the two Higgs doublets aesthetically into an irreducible representation of a SU(2)_H. By doing so, we get rid of the ad hoc discrete Z₂ symmetry which was usually put in by hand to guarantee a stable dark matter candidate in IHDM. In the literature, there are arguments suggesting quantum gravity effects may break any global symmetry, whether it is a discrete or continuous one. The G2HDM is a new version of 2HDM in the market. It is renormalizable and has very rich phenomenology, including various stable dark matter candidates guaranteed by local gauge symmetry, absence of flavor changing neutral currents (FCNC) at tree level, exotic gauge bosons, heavy Higgses, hidden heavy fermions, etc. We are just beginning to explore various phenomenological consequences of this model. This G2HDM is the most natural IHDM ever written down.
2. Lepton Flavor Violating Radiative Decays in EW-Scale Right-hand Neutrino Model. We studied the important charged lepton flavor violating (CLFV) process in a class of mirror fermion model. We performed this one-loop induced process on numerical analysis pinning down the parameter space of the model, which is most relevant to experiments. This process is very important for new physics search since CLFV processes are highly suppressed in the standard model (SM). This work is just the first of a series of papers concerning CLFV and FCNC interactions in mirror model. If this process as well as similar ones like muon-electron conversion,  FCNC top decays, and etc. can be observed experimentally in the next 10 years, it will definitely imply new physics beyond the SM. Experiments searching for CLFV processes are belonging to the high intensity frontiers, and they are complementarily to the high energy frontiers of LHC in search of new physics.

Researchers: Tzu-Chiang Yuan, Yue-Lin Sming Tsai, Raymundo Ramos