This study investigates the electroweak baryogenesis (EWBG) in the real singlet extension of the Standard Model (SM), including dimension-six operators, which couple the Higgs boson to a real singlet scalar field. We show that the electroweak phase transition is a one-step or a two-step phase transition, depending on the parameters of the singlet extension. In the majority of the parameter space, the electroweak phase transition proceeds as a two-step phase transition: an initial phase transition in the singlet sector at high temperatures, followed by a first-order phase transition in the Higgs sector. Interestingly, including the dimension-six operator, the electroweak phase transition occurs in regions of the parameter space, which were ruled out in the singlet extensions of the SM without the dimension-six operator. This is more evident for low singlet masses, which are excluded by the experimental constraints from the invisible decays of the Higgs boson. In addition, the real singlet extension explains the observed baryon asymmetry of the Universe introducing an additional source of \(CP\) violation in the SM via a second dimension-six operator, which contributes to the top-quark mass. These results provide new pathways for EWBG, expanding the viable parameter space for future collider and gravitational wave experiments, especially for low singlet masses.
An axion-like particle (ALP) offers a new direction in electroweak baryogenesis because the periodic nature enables it to trigger a strong first-order phase transition insensitively to the decay constant $f$. For $f$ much above TeV, the ALP-induced electroweak phase transition is approximately described by adiabatic processes, distinguishing our scenario for electroweak baryogenesis from the conventional ones. We show that, coupled to the electroweak anomaly, the ALP can naturally realize spontaneous electroweak baryogenesis to solve the matter-antimatter asymmetry problem for $f$ in the range…
We study the collider phenomenology of the electroweak phase transition and electroweak baryogenesis in the framework of the effective field theory. Our study shows that the effective theory using the dimension-6 operators can enforce strong first order phase transition and provide sizable CP violation to realize a successful electroweak baryogenesis. Such dimension-6 operators can induce interesting Higgs phenomenology that can be verified at colliders such as the LHC and the planning CEPC. We then demonstrate that this effective theory can originate from vector-like quarks and the triplet Hi…
We explore the possibility that the electroweak phase transition happens at a scale much higher than the electroweak scale today. In this context, high scale CP-violating sources for electroweak baryogenesis are not constrained by low-energy experiments. We propose a scenario of high-scale electroweak baryogenesis linked to flavour physics. This scenario allows for a period of enhanced Yukawa couplings during the evolution of the universe, which source time-dependent CP violation. The electroweak symmetry is never restored after the high-scale phase transition due to negative contributions to …
Electroweak baryogenesis is a simple and attractive candidate mechanism for generating the observed baryon asymmetry in the Universe. Its viability is sometimes investigated in terms of an effective field theory of the Standard Model involving higher dimension operators. We investigate the validity of such an effective field theory approach to the problem of identifying electroweak phase transitions strong enough for electroweak baryogenesis to be successful. We identify and discuss some pitfalls of this approach due to the modest hierarchy between mass scales of heavy degrees or freedom and t…
An axion can make the electroweak phase transition strongly first-order as required for electroweak baryogenesis even if it is weakly coupled to the Higgs sector. This is essentially because the axion periodicity naturally allows the structure of phase transition to be insensitive to the axion decay constant that determines the strength of axion interactions. Furthermore, the axion can serve as a CP phase relevant to electroweak baryogenesis if one introduces an effective axion coupling to the top quark Yukawa operator. Then, for $f$ between about TeV and order $10$~TeV, the observed baryon as…
The origin of the baryon asymmetry of the universe (BAU) is a longstanding problem in the high energy physics. The electroweak baryogenesis mechanism, which generates the BAU during the first order electroweak phase transition, provides a testable solution to this problem. In this paper we revisit the top-assisted electroweak baryogenesis model, which extends the standard model (SM) with only one scalar singlet. Constraints on the new CP-violating coupling as well as the mixing between the SM Higgs and the new scalar singlet are derived by considering the latest result of ACME and oblique obse…
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 $ρ_{tt}$ all of $\mathcal{O}$(1), one naturally has sizable $CP$ violation that fuels the cosmic baryon asymmetry. Even if $ρ_{tt}$ vanishes, the favor-changing coupling $ρ_{tc}$ can still lead to successful baryogenesis. Phenomenological consequences such as $t\to ch$, $τ\to μγ$, electron electric dipole moment, $h\toγγ$, and $hhh$ coupling are discuss…
