Electroweak symmetry in the early universe

  • June 3, 2021, 2:30 pm US/Central
  • Yikun Wang, U. Chicago
  • video

Behavior of the electroweak symmetry and the Higgs thermal history have intriguing implications for matter antimatter asymmetry creation and early universe physics. In this talk, I will present two beyond the Standard Model scenarios resulted in two different early universe paths of the electroweak symmetry. Electroweak phase transition from an electroweak symmetric phase to the electroweak broken phase, that happens around the electroweak scale, being strongly first order provides a necessary condition for electroweak baryogenesis, one of the most appealing mechanisms of generating the matter antimatter asymmetry, which is however, not the case within the Standard Model. As the first part of the talk, I will discuss a singlet extension of the Standard Model, where the singlet sector undergoes a spontaneous Z2 symmetry breaking, that would be compatible with a strongly first order electroweak phase transition at a temperature around the EW scale. On the other hand side, the novel possibility of electroweak symmetry non-restoration up to very high temperatures, could delay the asymmetry creation to an UV scale, allowing for rich model building possibilities. As the second part of the talk, I will discuss a new approach to realize such an scenario by transmitting the electroweak symmetry breaking from the SM sector at low temperatures to an inert Higgs sector at high temperatures, which couples to an additional singlet sector allowing for a negative thermal mass for the inert Higgs. As any new physics degrees of freedom coupling to the SM Higgs, those relevant for its thermal history, would also modify Higgs properties at zero temperature, they can be probed by current and future experiments, such as Higgs precision measurements, Higgs exotic decays etc. In this talk, I will also discuss the phenomenology for the two scenarios presented, to establish the connection between electroweak symmetry in the early universe and interesting Higgs property searches.