Abstract
The electroweak phase transition can be made first order by extending the Standard Model (SM) Higgs sector with extra scalars. The same new physics can explain the matter-antimatter asymmetry of the universe by supplying an extra source of CP violation and sphaleron processes. In this paper we study the existence of strong first order electroweak phase transition (SFOEWPT) in the type-I and type-II two Higgs doublet models (2HDM). We focus on how the SFOEWPT requirements constraint the spectrum of non-SM Higgs. Through the parameter space scan, we find that SFOEWPT suggests an upper limit on the masses of heavy Higgs {m}_{A/H/{H}^{pm }} , which is around 1 TeV. High temperature expansion and Higgs vacuum uplifting is used for an analytical understanding of our results. After taking into account the probe ability on SFOEWPT from theoretical constraints, Higgs and Z-pole precision measurements up to the one-loop level at future Higgs & Z factories, sizeable loop corrections require {m}_{A/{H}^{pm }}-{m}_H ∈ (100, 250) GeV to meet SFOEWPT condition for Type-II 2HDM, and left|{m}_{A/{H}^{pm }}-{m}_Hright| ∈ (100, 350) GeV or left|{m}_A-{m}_{H/{H}^{pm }}right| ∈ (100, 350) GeV for Type-I 2HDM.
Highlights
For a successful baryogenesis, new physics beyond the Standard Model (SM) (BSM) is required to supply a new source of CP violation and a strong out-of-equilibrium process [12, 13]
Through the parameter space scan, we find that strong first order electroweak phase transition (SFOEWPT) suggests an upper limit on the masses of heavy Higgs mA/H/H±, which is around 1 TeV
This makes the search for evidence of 2HDMs an endless game: you can never completely falsify a New Physics model containing hypothetical particles which have no upper limits on their mass
Summary
We need to emphasize that in the 2HDM we can set the mass of the non-SM Higgs bosons A/H/H± to an arbitrarily high scale This is because of the presence of m211,12,22, with m212 breaking Z2 symmetry in eq (2.1). Upper-limits on these terms are roughly given by 4πv2 ≈ (870 GeV)2 Another part of Higgs mass squares come from m212 (m211/22 are transformed through eq (2.3) and eq (2.4)), and these terms can in principle be set to any value without violating theoretical requirements. This makes the search for evidence of 2HDMs an endless game: you can never completely falsify a New Physics model containing hypothetical particles which have no upper limits on their mass. In the following part of this work we will show that the requirement of a SFOEWPT imposes upper limits on the masses of the A/H/H± bosons, making it possible to fully verify or falsify the idea of EWBG in 2HDMs in the near future
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