Orateur
Dr
Masaya Kohda
(National Taiwan University, Taiwan)
Description
We address the electroweak baryogenesis based on the standard model with a fourth generation. The conventional three-generation standard model (SM3) fails to explain the baryon asymmetry of the universe, although it can satisfy all three Sakharov’s conditions in principle. One of the reasons of this failure is the insufficiency of the CP violation from the Kobayashi-Maskawa phase. An existence of fourth generation quarks may solve this problem as new CP violating phases are introduced in the 4 by 4 Cabibbo-Kobayashi-Maskawa matrix. We investigate this possibility in the context of the Farrar-Shaposhnikov mechanism of the electroweak baryogenesis, where a baryon asymmetry is generated due to the CP violating scattering of quasi-particles, which are thermal excitations corresponding to the quarks and the antiquarks, with bubbles of the Higgs condensate. By assuming a strongly first-order electroweak phase transition and existence of bubbles, we demonstrate that the baryon asymmetry is highly enhanced compared to the SM3 case and can be large enough to explain the observed value, due mainly to the large masses of the fourth-generation quarks. We also argue the electroweak phase transition in the four generation case.
Author
Dr
Masaya Kohda
(National Taiwan University, Taiwan)
Co-auteurs
Prof.
Wei-Shu Hou
(National Taiwan University, Taiwan)
Prof.
Yoshio Kikukawa
(University of Tokyo, Japan)
