Speaker
Chikako Idegawa
(Ochanomizu university)
Description
We study the feasibility of strong first-order electroweak phase transition in a degenerate-scalar scenario of a complex singlet extension of the Standard Model, in which a mass of an additional scalar is nearly degenerate with that of the Higgs boson, 125 GeV. This scenario is known to be free from strong constraints from dark matter direct detection experiments due to cancellations between two scattering amplitudes mediated by two scalars. We point out that one of the conditions for the strong first-order EWPT is incompatible with the suppression mechanism of a dark matter cross-section scattering off the nucleons. Nevertheless, we find that strong first-order EWPT is still possible in the degenerate-scalar scenario.
