21 research outputs found
Chiral Invariance and Species Doublers in Generic Fermion Models on the Lattice
Discussions are made on the structures of chirally invariant lattice actions
without any restriction of hermiticity. With the help of the Ward-Takahashi
identity a general conclusion can be derived that there must be species
doublers in any chirally invariant model provided that the model is chosen as
well-regularized, that is, there is no singularity in the propagator after
introducing fermion mass on the lattice. Various examples are discussed to pick
up better models defined in the sense that the number of species doubler is
smaller than that of the naive Dirac action.Comment: 23 pages, 1 figure ( included
The Higgs sector in the Next-to-MSSM
We study the Higgs sector in the Next-to-Minimal Supersymmetric Standard
Model with and without explicit CP violation, focusing on the case of weak
scale expectation value of the singlet field. We scan a wide range of the
parameter space to find out allowed regions by requiring that the electroweak
vacuum be the global minimum of the effective potential and that the neutral
Higgs bosons with moderate gauge coupling be heavier than the lower bound on
the Higgs boson in the standard model. Among the allowed parameters, some sets
admit the situation in which the light Higgs bosons couple with the boson
too weak to be found in present collider experiments. For such parameter sets,
we find an upper bound on the charged Higgs mass which is reachable in LHC.Comment: 21 pages, 7 figure
Higgs Mass, CP Violation and Phase Transition in the MSSM
The effective potential in the MSSM at the one-loop level is used to evaluate
masses of the neutral Higgs scalars and to study finite-temperature phase
transition. The CP violation in the Higgs sector, which is induced by the
spontaneous mechanism or by the complex parameters in the MSSM through
radiative corrections, is determined at zero and finite temperatures.Comment: 27 pages, 16 EPS figures, uses LaTeX2
Transitional CP Violation in the MSSM and Electroweak Baryogenesis
Electroweak baryogenesis depends on the profile of the bubble wall created in
the first-order phase transition. It is pointed out that CP violation in the
Higgs sector of the MSSM could become large enough to explain the baryon
asymmetry. We confirm this by solving the equations of motion for the Higgs
fields with the effective potential at the transition temperature. That is, we
present an example such that the transitional CP violation is realized and show
the possibility that the baryon asymmetry of the universe may be produced, if
marginally, by the lepton interacting with the wall, when an explicit CP
breaking in the Higgs sector, which is consistent with experimental bounds, is
induced at the phase transition.Comment: LaTeX2e, 18 pages with 7 eps files of 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 and zero deep in the
broken- and the symmetric-phase regions, respectively, where 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,
, which would contribute to the
cosmological baryon asymmetry, is estimated for some typical profiles of the
wall, where () 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
The neutron and its role in cosmology and particle physics
Experiments with cold and ultracold neutrons have reached a level of
precision such that problems far beyond the scale of the present Standard Model
of particle physics become accessible to experimental investigation. Due to the
close links between particle physics and cosmology, these studies also permit a
deep look into the very first instances of our universe. First addressed in
this article, both in theory and experiment, is the problem of baryogenesis ...
The question how baryogenesis could have happened is open to experimental
tests, and it turns out that this problem can be curbed by the very stringent
limits on an electric dipole moment of the neutron, a quantity that also has
deep implications for particle physics. Then we discuss the recent spectacular
observation of neutron quantization in the earth's gravitational field and of
resonance transitions between such gravitational energy states. These
measurements, together with new evaluations of neutron scattering data, set new
constraints on deviations from Newton's gravitational law at the picometer
scale. Such deviations are predicted in modern theories with extra-dimensions
that propose unification of the Planck scale with the scale of the Standard
Model ... Another main topic is the weak-interaction parameters in various
fields of physics and astrophysics that must all be derived from measured
neutron decay data. Up to now, about 10 different neutron decay observables
have been measured, much more than needed in the electroweak Standard Model.
This allows various precise tests for new physics beyond the Standard Model,
competing with or surpassing similar tests at high-energy. The review ends with
a discussion of neutron and nuclear data required in the synthesis of the
elements during the "first three minutes" and later on in stellar
nucleosynthesis.Comment: 91 pages, 30 figures, accepted by Reviews of Modern Physic