189 research outputs found
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
Scattering with Baryon Number Violation -- The Case of Higgs Particle Production --
\noindent A formalism based on path-integral expression of time-evolution
operator during tunneling at a finite energy proposed by the authors is applied
to gauge-Higgs system to produce Higgs particles with .
Instead of starting from instanton tunneling at the zero energy, a classical
bounce solution giving sphaleron (instanton) action at high (low) energies is
used as the tunneling configuration. Fourier transform of the bounce
configuration in coherent state expression at the entrance and exit of the
tunneling plays an important role. Numerical results at various energies for
are given. Though the cross section with
results from a severe cancellation of several large quantities in the leading
order as occured in the instanton calculus, it seems unlikely that the cross
section grows as largely as to reach unitarity bound at energies . It is pointed out that the actual value of the
gauge coupling constant may be too large to take the weak coupling limit.}Comment: modified PHYZZX(included), 4 Figures (not included), SAGA-HE-46 :
KYUSHU-HET-
Phase Transitions in the NMSSM
We study phase transitions in the Next-to-Minimal Supersymmetric Standard
Model (NMSSM) with the weak scale vacuum expectation values of the singlet
scalar, constrained by Higgs spectrum and vacuum stability. We find four
different types of phase transitions, three of which have two-stage nature. In
particular, one of the two-stage transitions admits strongly first order
electroweak phase transition, even with heavy squarks. We introduce a
tree-level explicit CP violation in the Higgs sector, which does not affect the
neutron electric dipole moment. In contrast to the MSSM with the CP violation
in the squark sector, a strongly first order phase transition is not so
weakened by this CP violation.Comment: 21 pages, 8 figure
CP Violation in the Higgs Sector and Phase Transition in the MSSM
We investigate the electroweak phase transition in the presence of a large CP
violation in the squark sector of the MSSM. When the CP violation is large,
scalar-pseudoscalar mixing of the Higgs bosons occurs and a large CP violation
in the Higgs sector is induced. It, however, weakens first-order phase
transition before the mixing reaches the maximal. Even when the CP violation in
the squark sector is not so large that the phase transition is strongly first
order, the phase difference between the broken and symmetric phase regions
grows to O(1), which leads to successful baryogenesis, when the charged Higgs
bosons is light.Comment: 18 pages, 6 figures, LaTeX2
Charge Generation in the Oscillating Background
The preheating after the inflation, which can be interpreted as particle
creation in the oscillating inflaton background, provides a state far from
thermal equilibrium. We extend the field theoretical treatment of the
preheating by Linde et al. to the case of multicomponent complex scalars to
show that some charges are created in this process, if C and CP are violated. A
new possibility of baryogenesis based on this mechanism is also discussed.Comment: 18 pages, LaTeX 2e, 3 eps figure
Chiral Charge Flux and Electroweak Baryogenesis
By treating CP-violating interaction of the electroweak bubble wall as a
perturbative term, chiral charge flux through the bubble wall is estimated. It
is found that the absolute value of the flux has a sharp peak at with . Here
is the fermion mass, is the wall thickness, is the temperature
at which the bubbles are growing, is the wall velocity, is the
chiral charge of the relevant left(right)-handed fermion and is
the measure of CP violation.Comment: 10 pages, 4 figures ( not included, hard copies are available upon
request ), plain TeX with phyzzx
Numerical Approach to CP-Violating Dirac Equation
We propose a new method to evaluate the chiral charge flux, which is
converted into baryon number in the framework of the charge transport scenario
of electroweak baryogenesis. By the new method, one can calculate the flux in
the background of any type of bubble wall with any desired accuracy.Comment: 14 pages, epsf.sty is needed, 3 figures appende
CP Violating Bubble Wall and Electroweak Baryogenesis
The electroweak baryogenesis depends on the profile of the CP-violating
bubble wall created at the first order phase transition. We attempt to
determine it by solving the coupled equations of motion for the moduli and
phases of the two Higgs doublets at the transition temperature. A variety of
CP-violating bubble walls are classified by boundary conditions. We point out
that a sufficiently small explicit CP violation gives nonperturbative effects
to yield the baryon asymmetry of the universe.Comment: 19 pages, 6 EPS figures, uses epsf.st
Spontaneous CP Violation at Finite Temperature in the MSSM
By studying the effective potential of the MSSM at finite temperature, we
find that CP can be spontaneously broken in the intermediate region between the
symmetric and broken phases separated by the bubble wall created at the phase
transition. This type of CP violation is necessary to have a bubble wall
profile connecting CP conserving vacua, while violating CP halfway and
generating sufficient baryon number without contradiction to the experimantal
bounds on CP violations. Several conditions on the parameters in the MSSM are
found for CP to be broken in this manner.Comment: 26 pages, LaTeX, 16 eps figures (epsf.sty is needed
CP-violating profile of the electroweak bubble wall
In any scenario of the electroweak baryogenesis, the profile of the CP violating bubble wall, created at the first-order phase transition, plays an essential role. We attempt to determine it by solving the equations of motion for the scalars in the two-Higgs-doublet model at the transition temperature. According to the parameters in the potential, we found three solutions. Two of them smoothly connect the CP-violating broken phase and the symmetric phase, while the other connects CP-conserving vacua but violates CP in the intermediate region. We also estimate the chiral charge flux, which will be turned into the baryon density in the symmetric phase by the sphaleron process
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