We propose a framework where a phase transition associated with a gauge symmetry breaking that occurs (not far) above the electroweak scale sets a stage for baryogenesis similar to the electroweak baryogenesis in the Standard Model. A concrete realization utilizes the breaking of $SU(2)_R \times U(1)_X \rightarrow U(1)_Y$. New chiral fermions charged under the extended gauge symmetry have nonzero lepton numbers, which makes the $B-L$ symmetry anomalous. The new lepton sector contains a large flavor-dependent CP violation, similar to the Cabibbo-Kobayashi-Maskawa phase, without inducing sizable electric dipole moments of the Standard Model particles. A bubble wall dynamics associated with the first-order phase transition and $SU(2)_R$ sphaleron processes generate a lepton asymmetry, which is transferred into a baryon asymmetry via the ordinary electroweak sphaleron process. Unlike the Standard Model electroweak baryogenesis, the new phase transition can be of the strong first order and the new CP violation is not significantly suppressed by Yukawa couplings, so that the observed asymmetry can be produced. The model can be probed by collider searches for new particles and the observation of gravitational waves. One of the new leptons becomes a dark matter candidate. The model can be also embedded into a left-right symmetric theory to solve the strong CP problem.
Standard electroweak baryogenesis in the context of a first order phase transition is effective in generating the baryon asymmetry of the universe if the broken phase bubbles expand at subsonic speed, so that CP asymmetric currents can diffuse in front of the wall. Here we present a new mechanism for electroweak baryogenesis which operates for supersonic bubble walls. It relies on the formation of small bubbles of the symmetric phase behind the bubble wall, in the broken phase, due to the heating of the plasma as the wall passes by. We apply the mechanism to a model in which the Higgs field is…
We construct a model for delayed electroweak symmetry breaking that takes place in a cold Universe with T<<100 GeV and which proceeds by a fast quench rather than by a conventional, slow, phase transition. This is achieved by coupling the Standard Model Higgs to an additional scalar field. We show that the quench transition can be made fast enough for successful Cold Electroweak Baryogenesis, while leaving known electroweak physics unchanged.
The bubble wall velocity in an electroweak first order phase transition is a key quantity both for electroweak baryogenesis and for the production of a stochastic background of gravitational waves that may be probed in the future through gravitational wave experiments like LISA or BBO. We show that, contrary to the conclusion drawn from previous studies, it is actually possible to generate a potentially large gravitational wave signal while satisfying the requirements for viable electroweak baryogenesis, once the effects of the hydrodynamics of bubble growth are taken into account. Then, the o…
We re-evaluate the status of supersonic electroweak baryogenesis using a generalized fluid Ansatz for the non-equilibrium distribution functions. Instead of truncating the expansion to first order in momentum, we allow for higher order terms as well, including up to 21 fluctuations. The collision terms are computed analytically at leading-log accuracy. We also point out inconsistencies in the standard treatments of transport in electroweak baryogenesis, arguing that one cannot do without specifying an Ansatz for the distribution function. We present the first analysis of baryogenesis using the…
We analyse a simple extension of the SM with just an additional scalar singlet coupled to the Higgs boson. We discuss the possible probes for electroweak baryogenesis in this model including collider searches, gravitational wave and direct dark matter detection signals. We show that a large portion of the model parameter space exists where the observation of gravitational waves would allow detection while the indirect collider searches would not.
In light of the Higgs boson discovery we reconsider generation of the baryon asymmetry in the non-minimal split Supersymmetry model with an additional singlet superfield in the Higgs sector. We find that successful baryogenesis during the first order electroweak phase transition is possible within phenomenologically viable part of the model parameter space. We discuss several phenomenological consequences of this scenario, namely, predictions for the electric dipole moments of electron and neutron and collider signatures of light charginos and neutralinos.
It is widely believed that electroweak baryogenesis should be suppressed in strong phase transitions with fast-moving bubble walls, but this effect has never been quantitatively studied. We rederive fluid equations describing transport of particle asymmetries near the bubble wall without making the small-wall-velocity approximation. We show that the suppression of the baryon asymmetry is a smooth function of the wall speed and that there is no special behavior when crossing the sound speed barrier. Electroweak baryogenesis can thus be efficient also with strong detonations, generically associa…
We consider a real scalar singlet field which provides a strong first-order electroweak phase transition via its coupling to the Higgs boson, and gives a $CP$ violating contribution on the top quark mass via a dimension-6 operator. We study the correlation between the baryon-to-entropy ratio produced by electroweak baryogenesis, and the gravitational wave signal from the electroweak phase transition. We show that future gravitational wave experiments can test, in particular, the region of the model parameter space where the observed baryon-to-entropy ratio can be obtained even if the new physi…
We study stochastic gravitational wave production and baryon number generation at electroweak phase transition with the two Higgs doublet models. The produced stochastic gravitational wave during the strongly first-order phase transition can be probed by future space-based interferometers. The {\it nonlocal} electroweak baryogengesis cannot address the observed Baryon asymmetry of the Universe successfully in the strongly first-order phase transition parameter spaces due to the CP violation phase is severely bounded by the electron electric dipole moment measurement ACMEII.
We re-derive the vev-insertion approximation (VIA) source in electroweak baryogenesis. In contrast to the original derivation, we rely solely on 1-particle-irreducible self-energy diagrams. We solve the Green's function equations both perturbatively and resummed over all vev-insertions. The VIA source corresponds to the leading order contribution in the gradient expansion of the Kadanoff-Baym (KB) equations. We find that it vanishes both for bosons and fermions, both in the perturbative and in the resummed approach. Interestingly, the non-existence of the source is a result of a cancellation b…
It is conventional wisdom that successful electroweak baryogenesis in the Minimal Supersymmetric extension of the Standard Model (MSSM) is in tension with the non-observation of electric dipole moments (EDMs), since the level of CP-violation responsible for electroweak baryogenesis is believed to generate unavoidably large EDMs. We show that CP-violation in the bino-Higgsino sector of the MSSM can account for successful electroweak baryogenesis without inducing large EDMs. This observation weakens the correlation between electroweak baryogenesis and EDMs, and makes the bino-driven electroweak …
I review the status of the strength of the electroweak phase transition, and electroweak baryogenesis in the Minimal Supersymmetric Standard Model (work done with K. Kainulainen and M. Joyce). The emphasis is on new brane-inspired ideas about electroweak baryogenesis, and improvements in the semiclassical treatment of CP violation at a first order electroweak phase transition.
Adding an extra singlet scalar $S$ to the Higgs sector can provide a barrier at tree level between a false vacuum with restored electroweak symmetry and the true one. This has been demonstrated to readily give a strong phase transition as required for electroweak baryogenesis. We show that with the addition of a fermionic dark matter particle $χ$ coupling to $S$, a simple UV-complete model can realize successful electroweak baryogenesis. The dark matter gets a CP asymmetry that is transferred to the standard model through a $CP\ portal\ interaction$, which we take to be a coupling of $χ$ to $τ…
Electroweak baryogenesis is briefly overviewed with emphasis on nondecoupling loop properties of the scalar particles. In particular, quantum corrections to the triple Higgs boson coupling is discussed as a probe of electroweak baryogenesis.
The generation of the observed baryon asymmetry may have taken place during the electroweak phase transition, thus involving physics testable at LHC, a scenario dubbed electroweak baryogenesis. In this paper we point out that the magnetic field which is produced in the bubbles of a first order phase transition endangers the baryon asymmetry produced in the bubble walls. The reason being that the produced magnetic field couples to the sphaleron magnetic moment and lowers the sphaleron energy; this strengthens the sphaleron transitions inside the bubbles and triggers a more effective wash out of…
We describe electroweak monopoles within the Born-Infeld extension of $SU(2)_L\times U(1)_Y$ electroweak theory. We argue for topological stability of these monopoles and computed their mass in terms of the Born-Infeld mass parameters. We then propose a new mechanism for electroweak baryogenesis which takes advantage of the following salient features of the electroweak monopoles: (i) monopoles support extra CP violation in the topological sector of the electroweak theory; (ii) they mediate unsuppressed baryon number violating interactions; (iii) non-thermal production of monopoles during the e…
In this contribution we will shortly review the main mechanism through which primordial magnetic fields may affect the electroweak baryogenesis. It is shown that although strong magnetic fields might enhance the strength of the electroweak phase transition, no benefit is found for baryogenesis once the effect of the field on the sphaleron rate is taken into account. The possible role of hypermagnetic helicity for the electroweak baryogenesis is shortly discussed.
Cold electroweak baryogenesis was proposed as a scenario to bypass generic problems of electroweak baryogenesis within the Standard Model. In this scenario, baryogenesis takes place during an electroweak symmetry breaking transition, which is also responsible for preheating after inflation. In the simplest modelling of the scenario, only two parameters remain undetermined: The Higgs mass and the strength of CP violation. Using full real-time lattice simulations, we compute the dependence of the asymmetry on these parameters.
We consider origins of the baryon asymmetry which we observe today. We review the progress of electroweak-scale baryogenesis, and show a new mechanism, string-scale baryogenesis.
I review the mechanism of electroweak baryogenesis within the framework of a string motivated supersymmetric extension of the Standard Model with large flavor-independent CP-violating phases. Possible implications for the Higgs sector are considered in correlation with the properties of the right-handed stop. I also comment on the compatibility of supersymmetric electroweak baryogenesis with various CP-violating observables.
We consider feasibility of electroweak baryogenesis in gauge mediated supersymmetry breaking models with messenger-matter mixing. We present a class of models where electroweak baryogenesis produces sufficient amount of baryon asymmetry. The main features of these models are ({\it i}) large mixing between messengers and right stop and ({\it ii}) fairly narrow region of viable $\tanβ$.
We report a recent attempt to relate $CP$ violation in the electroweak theory with two Higgs doublets to the baryon asymmetry generated at the electroweak phase transition, after surveying the scenario of the electroweak baryogenesis.
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…
Baryogenesis at the electroweak phase transition is discussed within the framework of the supersymmetric standard model. Implications of baryon asymmetry for the electric dipole moment of the neutron are also studied.
In this talk, electroweak baryogenesis in the nMSSM is discussed. We focus on differences compared to the MSSM. We conclude that electroweak baryogenesis in the nMSSM is rather generic. Still, sfermions of the first two generations are required to be heavy to evade constraints from electric dipole moments.
I review recent progress on the electroweak phase transition and baryogenesis, focusing on the minimal supersymmetric standard model as the source of new physics.
We investigate scenarios in which electroweak baryogenesis can occur during an exotic stage of electroweak symmetry breaking in the early Universe. This transition is driven by the expectation value of a new electroweak scalar instead of the standard Higgs field. A later, second transition then takes the system to the usual electroweak minimum, dominated by the Higgs, while preserving the baryon asymmetry created in the first transition. We discuss the general requirements for such a two-stage electroweak transition to be suitable for electroweak baryogenesis and present a toy model that illus…
We study electroweak baryogenesis in the E_6 inspired exceptional supersymmetric standard model ( E_6SSM ). The relaxation coefficients driven by singlinos and the new gaugino as well as the transport equation of the Higgs supermultiplet number density in the E_6SSM are calculated. Our numerical simulation shows that both CP-violating source terms from singlinos and the new gaugino can solely give rise to a correct baryon asymmetry of the Universe via the electroweak baryogenesis mechanism.
Baryon asymmetry can be generated at the first order electroweak phase transition, provided there is a CP violation on the bubble wall. In this report we discuss the role of leptons and quarks in the `non-local' baryogenesis mechanism.
We demonstrate the viability of electroweak baryogenesis scenarios in which the necessary departure from equilibrium is realized by the evolution of a network of topological defects. We consider several effective models of TeV physics, each addressing a fundamental particle physics problem, and in which the conditions necessary for defect-mediated electroweak baryogenesis are naturally satisfied. In each case we compare the strength of the model with that expected from scenarios in which baryogenesis proceeds with the propagation of critical bubbles.
If stable electroweak strings are copiously produced during the electroweak phase transition, they may contribute significantly to the presently observed baryon to entropy ratio of the Universe. This analysis establishes the feasibility of implementing an electroweak baryogenesis scenario without a first order phase transition.
The status of electroweak baryogenesis in the minimal supersymmetric standard model is reviewed. I discuss the strength of the phase transition, CP violation and transport at the bubble walls, and the possibility of a two stage transition involving charge and color breaking.
We show that, for all values of $Tan β$ and the light right-handed stop mass for which the electroweak phase transition is strong enough to avoid washout following electroweak baryogenesis, the electroweak vacuum is stable over the lifetime of the observed Universe. Cosmological stability of the electroweak vacuum is violated only if the light right-handed stop is lighter than 100-115GeV.
We examine a recent claim that Debye screening will affect the charge transport mechanism of anomalous electroweak baryogenesis. We show that the effects of gauge charge screening do not affect the baryon number produced during a first order electroweak phase transition. (Requires harvmac.tex)
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 review the mechanism of electroweak baryogenesis. Our focus is on the derivation of quantum transport equations from first principles within the Schwinger-Keldysh formalism. We emphasize the importance of the semiclassical force approach, which provides reliable predictions in most models. In the light of recent electric dipole moment measurements and given the results on new physics searches from collider experiments, the status of electroweak baryogenesis is discussed in a variety of models.
The standard picture of electroweak baryogenesis requires slowly expanding bubbles. This can be difficult to achieve if the vacuum expectation value of a gauge singlet scalar field changes appreciably during the electroweak phase transition. It is important to determine the bubble wall velocity in this case, since the predicted baryon asymmetry can depend sensitively on its value. Here, this calculation is discussed and illustrated in the real singlet extension of the Standard Model. The friction on the bubble wall is computed using a kinetic theory approach and including hydrodynamic effects.…
We use transport equations to compute the evolution of the quark plasma at the electroweak phase transition in the two-doublet Higgs model, obtaining in a more rigorous and quantitatively accurate way results consistent with previous work. We discuss the model in connection with the electroweak baryogenesis scenario, and claim that the observed baryon asymmetry of the universe can be obtained within this model with a suitable choice of parameters.
We analyze the spontaneous baryogenesis and charge transport mechanisms suggested by Cohen, Kaplan and Nelson for baryon asymmetry generation in extended versions of electroweak theory. We find that accounting for non-perturbative chirality-breaking transitions due to strong sphalerons reduces the baryonic asymmetry by the factor $(m_t/πT)^2$ or $α_W$, provided those processes are in thermal equilibrium.
If stable electroweak strings are copiously produced during the electroweak phase transition, they may contribute significantly to the presently observed baryon to entropy ratio of the universe. This analysis establishes the feasibility of implementing an electroweak baryogenesis scenario without a first order phase transition.
We study electric dipole moment bounds on CP-violating phases in the MSSM with special emphasis on the cancelation scenario. We find that in the range favored by electroweak baryogenesis ({\it i.e.,} $|μ|\simeq M_1$ or $|μ|\simeq M_2$), $\sin [θ_μ+θ_{M_1}]$ can be as large as ${\cal O}(1)$, even for slepton masses below 500 GeV. Such large values of the phases promise a successful electroweak baryogenesis. We also discuss the possibility of large CP-odd effects at a linear collider.
We develop a new and general method to calculate the effects of \cp\ violation from extensions of the standard model on the mechanism of electroweak baryogenesis. We illustrate its applicability in the framework of two-higgs doublet models.
The possibility of electroweak baryogenesis is considered within the framework of a left-right supersymmetric model. It is shown that for a range of parameters the large sneutrino VEV required for parity breaking varies at the electroweak phase transition leading to a production of baryons. The resulting baryon to entropy ratio is approximated to be ${n_B\over s}\sim α0.7 \times10^{-8}$, where $α$ is the angle that the phase of sneutrino VEV changes at the electroweak phase transition.
We initiate a study of cosmological implications of sphaleron-mediated CP-violation arising from the electroweak vacuum angle under the reasonable assumption that the semiclassical suppression is lifted at finite temperature. In this article, we explore the implications for existing scenarios of baryogenesis. Many compelling models of baryogenesis rely on electroweak sphalerons to relax a $(B+L)$ charge asymmetry. Depending on the sign of the CP-violating parameter, it is shown that the erasure of positive $(B+L)$ will proceed more or less quickly than the relaxation of negative $(B+L)$. This …
Pedagogical lectures on baryogenesis, with emphasis on the electroweak phase transition and electroweak baryogenesis. Contents: (1) Observational evidence for the BAU; (2) Sakharov's conditions for baryogenesis; (3) Example: GUT baryogenesis; (4) B and CP violation in the standard model; (5) Electroweak phase transition and electroweak baryogenesis; (6) A model of electroweak baryogenesis: the two Higgs doublet model; (7) EWBG in the MSSM; (8) Leptogenesis
We discuss some recent developments made in the computation of the baryon asymmetry generated at the electroweak scale. We emphasize that the local number density asymmetries of the particles involved in supersymmetric electroweak baryogenesis must be described by a set of Quantum Boltzmann Equations. These diffusion equations automatically and self-consistently incorporate the CP-violating sources which fuel baryogenesis and manifest ``memory'' effects which are typical of the quantum transport theory and are not present in the classical approach.
Baryogenesis during the electroweak phase transition is a plausible scenario for for the origin of matter in the Universe. Furthermore, it has the advantage over other scenarios in that one can imagine that much of the physics involved may be experimentally probed before long. In the past year a consensus has developed about major mechanisms involved. In this talk I give an overview of the standard picture, and discuss briefly the advances over the past year that suggest electroweak baryogenesis is a robust phenomenon.
The presence of a primordial magnetic field in the early universe affects the dynamic of the electroweak phase transition enhancing its strength. This effect may enlarge the window for electroweak baryogenesis in the minimal supersymmetric extension of the standard model or even resurrect the electroweak baryogenesis scenario in the standard model. We compute the sphaleron energy in the background of the magnetic field and show that, due to the sphaleron dipole moment, the barrier between topologically inequivalent vacua is lowered. Therefore, the preservation of the baryon asymmetry calls for…
We consider the scenario of electroweak baryogenesis mediated by cosmological defect in models of supersymmetry breaking. When the effective electroweak breaking scale is raised in the defect configuration, the mechanism of electroweak baryogenesis works at a higher energy scale. The baryon charge produced by the mechanism is captured in the defect, protected from sphalerons and then released when the defect decay.
We study on the electroweak baryogenesis problem in the vector-like quark model. This model can add to the minimal standard model the extra CP-violation source which breaks CP spontaneously. Using charge transport mechanism suggested by Nelson et al, we can get the net hypercharge flux : $f_{Y} \sim 10^{-5}$. This result could nicely explain the present baryon to entropy ratio : $ρ_{B}/s \sim 10^{-9}$.
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 …
We propose a new scenario of the electroweak baryogenesis based on the properties of electroweak domain walls surrounding black holes in the Higgs phase vacuum of the extended Standard Model with 2-Higgs doublets. It is shown that there exists the electroweak domain walls and the symmetric regions surrounding black holes and that the Hawking radiation of the black holes can produce a non-zero baryon number density. The scenario can explain the origin of the baryon number in our universe even without the assumption of the existence of the first order electroweak phase transition.
In the defect-mediated electroweak baryogenesis scenario, baryons are produced in well separated regions of space. It is shown that between the electroweak phase transition at a temperature of $T \sim 100 {\rm GeV}$ and the end of nucleosynthesis at $T \sim 1 {\rm KeV}$ the baryon inhomogeneities dissipate, and that no constraints on defect-mediated electroweak baryogenesis can be derived from considerations of inhomogeneous nucleosynthesis.
In models of thick wall electroweak baryogenesis a common assumption is that the plasma interacting with the expanding Higgs bubble wall during the electroweak phase transition is in kinetic equilibrium (or close to it). We point out that, in addition to the requirement of low wall velocity, kinetic equilibrium requires that the change in the momentum of the particles due to the force exerted by the wall should be much less than that due to scattering as the plasma passes through the wall. We investigate whether this condition is satisfied for charginos and neutralinos participating in thick w…
We study collider signatures of electroweak baryogenesis in the two Higgs doublet model and the minimal supersymmetric standard model. It is found that the trilinear coupling of the lightest Higgs boson receives large quantum corrections if the electroweak phase transition is strongly first order for successful baryogenesis. In the two Higgs doublet model, the magnitude of the deviation from the standard model value is shown to be larger than 10 percent. Such a deviation can be detected at a future electron-positron linear collider.
I report on a critical analysis of the scenario of electroweak baryogenesis mediated by nonsuperconducting cosmic strings. This mechanism relies upon electroweak symmetry restoration in a region around cosmic strings, where sphalerons would be unsuppressed. I discuss the various problems this scenario has to face, presenting a careful computation of the sphaleron rates inside the strings, of the chemical potential for chiral number and of the efficiency of baryogenesis in different regimes of string networks. The conclusion is that the asymmetry in baryon number generated by this scenario is s…
