Sphaleron and critical bubble in the scale invariant two Higgs doublet model

We revisit the electroweak phase transition and the critical bubble in the scale invariant two Higgs doublet model in the light of recent LHC data. Moreover, the sphaleron decoupling condition is newly evaluated in this model. The analysis is done by using the resummed finite-temperature one-loop effective potential. It is found that the 125 GeV Higgs boson inevitably leads to the strong first-order electroweak phase transition, and the strength of which is always large enough to satisfy the sphaleron decoupling condition, v(N)/T-N > 1.2, where T-N denotes a nucleation temperature and V-N is the Higgs vacuum expectation value at T-N. In this model, even if the Higgs boson couplings to gauge bosons and fermions are similar to the standard model values, the signal strength of the Higgs decay to two photons is reduced by 10% and the triple Higgs boson coupling is enhanced by 82% compared to the standard model prediction. (C) 2015 The Authors. Published by Elsevier B.V.