Electroweak phase transition in the MSSM with four generations

By assuming the existence of the sequential fourth generation to the minimal supersymmetric standard model (MSSM), we study the possibility of a strongly first-order electroweak phase transition. We find that there is a parameter region of the MSSM where the electroweak phase transition is strongly first order. In that parameter region, the mass of the lighter scalar Higgs boson is calculated to be above the experimental lower bound, and the scalar quarks of the third and the fourth generations are heavier than the corresponding quarks.Comment: 12 pages, 2 tables, 2 figure

Fermion Scattering off CP-Violating Electroweak Bubble Wall

A general prescription to solve the Dirac equation in the presence of CP-violating electroweak bubble wall is presented. The profile of the bubble wall is not specified except that the wall height is $m_0$ and zero deep in the broken- and the symmetric-phase regions, respectively, where $m_0$ is a fermion mass given by the Higgs-vacuum-expectation value and the Yukawa coupling. The CP-violating effects are evaluated by regarding CP-violating part of the bubble wall as a perturbation to CP-conserving solutions. The basic quantity, $R_{R\rightarrow L}-\bar R_{R\rightarrow L}$, which would contribute to the cosmological baryon asymmetry, is estimated for some typical profiles of the wall, where $R_{R\rightarrow L}$($\bar R_{R\rightarrow L}$) is the reflection coefficient of right-handed chiral fermion (anti-fermion).Comment: 30 pages, 2 figures ( uuencoded tar.Z file of PS files is appended ), plain TeX with phyzzx, tables and epsf,SAGA-HE-55--KYUSHU-HET-1

Determining the global minimum of Higgs potentials via Groebner bases - applied to the NMSSM

Determining the global minimum of Higgs potentials with several Higgs fields like the next-to-minimal supersymmetric extension of the Standard Model (NMSSM) is a non-trivial task already at the tree level. The global minimum of a Higgs potential can be found from the set of all its stationary points defined by a multivariate polynomial system of equations. We introduce here the algebraic Groebner basis approach to solve this system of equations. We apply the method to the NMSSM with CP conserving as well as CP violating parameters. The results reveal an interesting stationary-point structure of the potential. Requiring the global minimum to give the electroweak symmetry breaking observed in Nature excludes large parts of the parameter space.Comment: 10 pages, 2 figure

Higgs coupling constants as a probe of new physics

We study new physics effects on the couplings of weak gauge bosons with the lightest CP-even Higgs boson ($h$), $hZZ$, and the tri-linear coupling of the lightest Higgs boson, $hhh$, at the one loop order, as predicted by the two Higgs doublet model. Those renormalized coupling constants can deviate from the Standard Model (SM) predictions due to two distinct origins; the tree level mixing effect of Higgs bosons and the quantum effect of additional particles in loop diagrams. The latter can be enhanced in the renormalized $hhh$ coupling constant when the additional particles show the non-decoupling property. Therefore, even in the case where the $hZZ$ coupling is close to the SM value, deviation in the $hhh$ coupling from the SM value can become as large as plus 100 percent, while that in the $hZZ$ coupling is at most minus 1 percent level. Such large quantum effect on the Higgs tri-linear coupling is distinguishable from the tree level mixing effect, and is expected to be detectable at a future linear collider.Comment: 52 pages, 10 figures, revtex

Finite Temperature Renormalization of the (ϕ3)6(\phi^3)_6- and (ϕ4)4(\phi^4)_4-Models at Zero Momentum

A self-consistent renormalization scheme at finite temperature and zero momentum is used together with the finite temperature renormalization group to study the temperature dependence of the mass and the coupling to one-loop order in the $(\phi^3)_6$- and $(\phi^4)_4$-models. It is found that the critical temperature is shifted relative to the naive one-loop result and the coupling constants at the critical temperature get large corrections. In the high temperature limit of the \phiff-model the coupling decreases.Comment: 16 pages, plain Latex, NORDITA-92/38

Additional phases induced by the supersymmetric CP phases

The explicit CP violation in the MSSM radiatively induces a finite unremovable alignment between the Higgs doublets. This additinal phase can be as large as the original CP phases in certain portions of the MSSM parameter space. Considering the specific case of the charginos, this additional phase is shown to induce a conceivable amount of CP violation near the would--be CP conserving points. Moreover, the CP violation in the absence of this phase is smaller than the one in the presence of it, and the former can never compete with the latter, however large $\tan\beta$ is.Comment: 29 pp, 15 fig

Electroweak phase transitions in the secluded U(1)-prime-extended MSSM

The electroweak phase transition (EWPT) in the secluded-$U(1)'$-extended MSSM (sMSSM) is studied. Using the effective potential at zero and finite temperatures, we search for the non-MSSM-like EWPT in which the light stop mass is larger than the top quark mass. Scanning the parameters relevant to the EWPT, the upper limits of the Higgs boson masses, which are consistent with the strong first order EWPT, are derived. For the lightest CP-even and -odd Higgs bosons, we find $m_{H_1}<160$ GeV and $m_{A_1}<250$ GeV, respectively. In the sMSSM, the tree-level CP violation is possible by the complex soft supersymmetry breaking masses. It is observed that such a CP-violating effect does not spoil the strong first order EWPT for the typical parameter sets.Comment: 29 pages,15 figures, JHEP style; accepted for publication in JHE

Mixing-induced CP violating sources for electroweak baryogenesis from a semiclassical approach

The effects of flavor mixing in electroweak baryogenesis is investigated in a generalized semiclassical WKB approach. Through calculating the nonadiabatic corrections to the particle currents it is shown that extra CP violation sources arise from the off-diagonal part of the equation of motion of particles moving inside the bubble wall. This type of mixing-induced source is of the first order in derivative expansion of the Higgs condensate, but is oscillation suppressed. The numerical importance of the mixing-induced source is discussed in the Minimal Supersymmetric Standard Model and compared with the source term induced by semiclassical force. It is found that in a large parameter space where oscillation suppression is not strong enough, the mixing-induced source can dominate over that from the semiclassical force.Comment: 19 pp, 2 figs, 1 table, some comments added, to appear in Eur.Phys.J.

Perturbative analysis for Kaplan's lattice chiral fermions

Perturbation theory for lattice fermions with domain wall mass terms is developed and is applied to investigate the chiral Schwinger model formulated on the lattice by Kaplan's method. We calculate the effective action for gauge fields to one loop, and find that it contains a longitudinal component even for anomaly-free cases. From the effective action we obtain gauge anomalies and Chern-Simons current without ambiguity. We also show that the current corresponding to the fermion number has a non-zero divergence and it flows off the wall into the extra dimension. Similar results are obtained for a proposal by Shamir, who used a constant mass term with free boundaries instead of domain walls.Comment: 25 page, 5 PostScript figures, [some changes in the conclusion

Inflationary Baryogenesis

In this letter we explore the possibility of creating the baryon asymmetry of the universe during inflation and reheating due to the decay of a field associated with the inflaton. CP violation is attained by assuming that this field is complex with a phase that varies as the inflaton evolves. We consider chaotic and natural inflation scenarios. In the former case, the complex decaying field is the inflaton itself and, in the latter case, the phase of the complex field is the inflaton. We calculate the asymmetry produced using the Bogolyubov formalism that relates annihilation and creation operators at late time to the annihilation and creation operators at early time.Comment: 17 pages, Revte