Seminar 
Title: Perturbative constraints on the U(1) and left-right models and phenomenological implications 
Speaker: Dr. Yongchao Zhang (Washington University in St. Louis） 
Time: 10:00 AM, Jan. 15th (Tuesday), 2019 
Place: R319, Theoretical Physics Division 

Abstract: In the scenarios where the Standard Model gauge group is extended, the additional gauge couplings can not be arbitrarily large and/or small if it contributes to the electric charge. This is from the requirement that the couplings remain perturbative up to the GUT or Planck scale, which leads to stringent constraints on the masses of the corresponding gauge bosons and their collider phenomenology. In the U(1)_{B-L} model, the mass of heavy ZR boson is constrained to be within a narrow window. In the left-right model, due to the extra stringent limits from the scalar sector, the right-handed scale is required to be larger than roughly 10 TeV, if all the gauge and scalar quartic couplings are perturbative up to the GUT scale. This precludes the prospects of finding the ZR boson in the left-right model at the LHC, even in the high-luminosity phase, and leaves only a narrow window for the WR boson. A much broader allowed parameter space, with the right-handed scale vR up to 87 TeV, could be probed at the future 100 TeV collider.