We evaluate dominant two-loop corrections to the triple Higgs coupling and strength of a first-order electroweak phase transition in the inert Higgs doublet model. It is found that sunset diagrams ...can predominantly enhance the former and reduce the latter. As a result, the triple Higgs coupling normalized by the standard model value at two-loop level is more enhanced than the corresponding one-loop value.
Symmetries at finite temperature are of great importance to understand dynamics of spontaneous symmetry breaking phenomena, especially phase transitions in early Universe. Some symmetries such as the ...electroweak symmetry can be restored in hot environment. However, it is a nontrivial question that the phase transition occurs via first or second order, or even smooth crossover, which strongly depends on underlying physics. If it is first order, gravitational waves can be generated, providing a detectable signal of this epoch. Moreover, the baryon asymmetry of the Universe can also arise under some conditions. In this article, the electroweak phase transition is reviewed, focusing particularly on the case of the first-order phase transition. Much attention is paid to multi-step phase transitions in which additional symmetry breaking such as a spontaneous Z 2 breaking plays a pivotal role in broadening the possibility of the first-order electroweak phase transition. On the technical side, we review thermal resummation that mitigates a bad infrared behavior related to the symmetry restoration. In addition, gauge and scheme dependences of perturbative calculations are also briefly discussed.
We consider a scenario in which an extra bottom Yukawa coupling can drive electroweak baryogenesis in the general two-Higgs doublet model. It is found that the new bottom Yukawa coupling with O(0.1) ...in magnitude can generate the sufficient baryon asymmetry without conflicting existing data. We point out that future measurements of the bottom Yukawa coupling at High-Luminosity Large Hadron Collider and International Linear Collider, together with the CP asymmetry of B→Xsγ at SuperKEKB provide exquisite probes for this scenario.
We improve the sphaleron decoupling condition in the real singlet-extended standard model (SM). The sphaleron energy is obtained using the finite-temperature one-loop effective potential with daisy ...resummation. For moderate values of the model parameters, the sphaleron decoupling condition is found to be upsilon sub(C)/T sub(C) > (1.1 - 1.2), where T sub(C) denotes a critical temperature and upsilon sub(C) is the corresponding vacuum expectation value of the doublet Higgs field at T sub(C). We also investigate the deviation of the triple Higgs boson coupling from its standard model value in the region where the improved sphaleron decoupling condition is satisfied. As a result of the improvement, the deviation of the triple Higgs boson coupling gets more enhanced. In a typical case, if the Higgs couplings to the gauge bosons/fermions deviate from the SM values by about 3 (10)%, the deviation of the triple Higgs boson coupling can be as large as about 16 (50)%, which is about 4 (8)% larger than that based on the conventional criterion upsilon sub(C) /T sub(c) > 1.
A
bstract
We study the prospect of probing electroweak baryogenesis driven by an extra bottom Yukawa coupling
ρ
bb
in a general two Higgs doublet model via electric dipole moment (EDM) measurements ...and at the collider experiments. The parameter space receives meaningful constraints from 125 GeV Higgs
h
boson signal strength measurements as well as several heavy Higgs boson searches at the Large Hadron Collider (LHC). In addition, we show that the asymmetry of the CP asymmetry of inclusive
B → X
s
γ
decay would provide complementary probe. A discovery is possible at the LHC via
bg → bA → bZh
process if |
ρ
bb
| ∼ 0
.
15 and 250 GeV≲
m
A
≲ 350 GeV, where
A
is CP odd scalar. For
m
A
>
2
m
t
threshold, where
m
t
is the top quark mass, one may also discover
bg → bA →
bt
t
¯
at the high luminosity LHC run if an extra top Yukawa coupling |
ρ
tt
| ∼ 0
.
5, though it may suffer from systematic uncertainties. For completeness we study
gg →
t
t
¯
A
→
t
t
¯
b
b
¯
but find it not promising.
We study the possibility of electroweak baryogenesis in the standard model with a complex scalar field, focusing mainly on a degenerate scalar scenario. In our setup, CP violation is provided by ...dimensional-5 Yukawa interactions involving the complex scalar field. In contrast to previous studies in the literature, we exemplify a case in which a complex phase in the singlet scalar potential is transmitted to the fermion sector via the higher-dimensional operators and drives BAU. We point out that an electric dipole moment of the electron can be suppressed due to the Higgs mass degeneracy and the presence of a new electron Yukawa coupling. Thus, viable parameter space for electroweak baryogenesis is still wide open for the latest experimental bound set by the JILA Collaboration.
We study electroweak baryogenesis driven by the top quark in a general two Higgs doublet model with flavor-changing Yukawa couplings, keeping the Higgs potential CP invariant. With Higgs sector ...couplings and the additional top Yukawa coupling ρtt all of O(1), one naturally has sizable CP violation that fuels the cosmic baryon asymmetry. Even if ρtt vanishes, the favor-changing coupling ρtc can still lead to successful baryogenesis. Phenomenological consequences such as t→ch, τ→μγ electron electric dipole moment, h→γγ, and hhh coupling are discussed.
We study the complementarity between the Large Hadron Collider (LHC) and future lepton colliders in probing electroweak baryogenesis induced by an additional bottom Yukawa coupling ρbb. The context ...is general two Higgs doublet model (g2HDM) where such additional bottom Yukawa coupling can account for the observed baryon asymmetry of the Universe if Im(ρbb)≳0.058. We find that LHC would probe the nominal Im(ρbb) required for baryogenesis to some extent via bg→bA→bZh process if 300GeV≲mA≲450 GeV, where A is the CP-odd scalar in g2HDM. We show that future electron positron collider such as International Linear Collider with 500 GeV and 1 TeV collision energies may offer unique probe for the nominal Im(ρbb) via e+e−→Z⁎→AH process followed by A,H→bb¯ decays in four b-jets signature. For complementarity we also study the resonant diHiggs productions, which may give an insight into strong first-order electroweak phase transition, via e+e−→Z⁎→AH→Ahh process in six b-jets signature. We find that 1 TeV collision energy with O(1)ab−1 integrated luminosity could offer an ideal environment for the discovery.
We study gauge dependence of gravitational waves produced from a first-order phase transition in classical scale-invariant U(1)′ models. Accidental gauge independence of the one-loop effective ...potential in this class of models is spoiled by including thermal resummation. The gauge artifact in the resummed effective potential propagates to the gravitational wave spectrum and results in one order of magnitude uncertainties in the prediction under a specific gauge choice.
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, vN/TN>1.2, where TN denotes a nucleation temperature and vN is the Higgs vacuum expectation value at TN. 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.
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