Gravitational waves and Higgs boson couplings for exploring first order phase transition in the model with a singlet scalar field

Abstract

We calculate the spectrum of gravitational waves originated from strongly\nfirst order electroweak phase transition in the extended Higgs model with a\nreal singlet field. In order to calculate the bubble nucleation rate, we\nperform a two-field analysis to evaluate bounce solutions connecting the true\nand the false vacua using the one-loop effective potential at finite\ntemperatures. Imposing the Sakharov condition of the departure from thermal\nequilibrium for baryogenesis, we survey allowed regions of parameters of the\nmodel. We then investigate the gravitational waves produced at electroweak\nbubble collisions in the early Universe, such as the sound wave, the bubble\nwall collision and the plasma turbulence. We find that the strength at the peak\nfrequency can be large enough to be detected at future space-based\ngravitational interferometers such as eLISA, DECIGO and BBO. Predicted\ndeviations in the various Higgs boson couplings are also evaluated at the zero\ntemperature, and are shown to be large enough too. Therefore, in this model\nstrongly first order electroweak phase transition can be tested by the\ncombination of the precision study of various Higgs boson couplings at LHC, the\nmeasurement of the triple Higgs boson coupling at future lepton colliders and\nthe shape of the spectrum of gravitational wave detectable at future\ngravitational interferometers.\n