21 research outputs found
Vacuum stability and the Cholesky decomposition
We discuss how the Cholesky decomposition may be used to ascertain whether a
critical point of the field theory scalar potential provides a stable vacuum
configuration. We then use this method to derive the stability conditions in a
specific example.Comment: 7 page
Anatomy of Mixing-Induced CP Asymmetries in Left-Right-Symmetric Models with Spontaneous CP Violation
We investigate the pattern of CP violation in K, B_d and B_s mixing in a
symmetrical SU(2)_R x SU(2)_L x U(1) model with spontaneous CP violation. We
calculate the phases of the left and right quark mixing matrices beyond the
small phase approximation and perform a careful analysis of all relevant
restrictions on the model's parameters from Delta m_K, Delta m_B, epsilon,
epsilon'/epsilon and the CP asymmetry in B->J/psi K_S. We find that, with
current experimental data, the mass of the right-handed charged gauge boson,
M2, is restricted to be in the range 2.75 to 13 TeV and the mass of the
flavour-changing neutral Higgs boson, MH, in 10.2 to 14.6 TeV. This means in
particular that the decoupling limit M2, MH -> infinity is already excluded by
experiment. We also find that the model favours opposite signs of epsilon and
sin 2beta and is excluded if sin 2beta > 0.1.Comment: 33 pages Latex with 11 Postscript-Figures (included
The Minimal Left-Right Symmetric Model and Radiative Corrections to the Muon Decay
A self-consistent version of the left-right (LR) symmetric model is used to
examine tree- as well as one-loop level radiative corrections to the muon
decay. It is shown that constraints on the heavy sector of the model parameters
are different when going beyond tree-level physics. In fact, in our case, the
only useful constraints on the model can be obtained from the one-loop level
calculation. Furthermore, corrections coming from the subset of SM particles
within the LR model have a different structure from their SM equivalent, e.g.
the top quark leading term contribution to within the LR model is
different from its SM counterpart. As a consequence, care must be taken in
fitting procedures of models beyond the SM, where usually, only tree-level
couplings modified by the SM radiative corrections are considered. This
procedure is not always correct.Comment: small corrections, final version for proceeding
Muon Decay to One Loop Order in the Left-Right Symmetric Model
One loop corrections to the muon decay are studied in a popular and
self-consistent version of the Left-Right symmetric model. It is shown
quantitatively, that the corrections do not split into those that come from the
Standard Model sector and some decoupling terms. For a heavy Spontaneous
Symmetry Breaking (SSB) scale of the order of a least 1 TeV, the contributions
from the top quark have a logarithmic behaviour and there is a strong quadratic
dependence on the heavy Higgs scalar masses. The dependence on the light Higgs
boson mass is small. The heavy neutrinos are shown to play an important role,
although secondary in comparison with the heavy scalar particles as long as the
heavy neutrinos' Majorana Yukawa coupling matrix obeys unitarity bounds.Comment: 20 pages, 7 figure
Higgs Sector of the Minimal Left-Right Symmetric Model
We perform an exhaustive analysis of the most general Higgs sector of the
minimal left-right symmetric model (MLRM). We find that the CP properties of
the vacuum state are connected to the Higgs spectrum: if CP is broken
spontaneously, the MLRM does not approach the Standard Model in the limit of a
decoupling left-right symmetry breaking scale. Depending on the size of the CP
phases scenarios with extra non-decoupling flavor-violating doublet Higgses or
very light SU(2) triplet Higgses emerge, both of which are ruled out by
phenomenology. For zero CP phases the non-standard Higgses decouple only if a
very unnatural fine-tuning condition is fulfilled. We also discuss
generalizations to a non-minimal Higgs sector.Comment: brief discussion of non-minimal Higgs sectors added, journal versio
On Neutrino Masses and a Low Breaking Scale of Left-Right Symmetry
In left-right symmetric models (LRSM) the light neutrino masses arise from
two sources: the seesaw mechanism and a VEV of an SU(2) triplet. If the
left-right symmetry breaking, , is low, v_R\lsim15\TeV, the
contributions to the light neutrino masses from both the seesaw mechanism and
the triplet Yukawa couplings are expected to be well above the experimental
bounds. We present a minimal LRSM with an additional U(1) symmetry in which the
masses induced by the two sources are below the eV scale and the two-fold
problem is solved. We further show that, if the U(1) symmetry is also
responsible for the lepton flavor structure, the model yields a small mixing
angle within the first two lepton generations.Comment: 18 pages references added published versio
Spontaneous CP violation in the left-right model and the kaon system
A left-right model with spontaneous CP breakdown, consistent with the particle physics phenomenology, is presented. Constraints on free parameters of the model: mass of the new right handed gauge boson M2 and ratio r of the two vacuum expectation values of the bidoublet, are found from the measurement of ϵ in the kaon system. For most of the parameter space, M2 is restricted to be below 10 TeV. Higher masses can be achieved only by fine tuning of Kobayashi-Maskawa matrix elements, quark masses, r and the phase α which is the unique source of CP-violation in the model. Large number of combinations of signs of quark masses, which are observables of the model, are found to be not allowed since they contradict with data. The range of ϵ′/ϵ the model predicts is around 10−4 in magnitude
Two Higgs Bi-doublet Left-Right Model With Spontaneous P and CP Violation
A left-right symmetric model with two Higgs bi-doublet is shown to be a
consistent model for both spontaneous P and CP violation. The flavor changing
neutral currents can be suppressed by the mechanism of approximate global U(1)
family symmetry. We calculate the constraints from neural meson mass
difference and demonstrate that a right-handed gauge boson
contribution in box-diagrams with mass well below 1 TeV is allowed due to a
cancellation caused by a light charged Higgs boson with a mass range GeV. The contribution to can be suppressed from
appropriate choice of additional CP phases appearing in the right-handed
Cabbibo-Kobayashi-Maskawa matrix. The model is also found to be fully
consistent with mass difference , and the mixing-induced CP
violation quantity , which is usually difficult for the
model with only one Higgs bi-doublet. The new physics beyond the standard model
can be directly searched at the colliders LHC and ILC.Comment: 25 pages, 6 figures, typos corrected, 1 figure added, published
versio
Minimal SUSY SO(10) model and predictions for neutrino mixings and leptonic CP violation
We discuss a minimal Supersymmetric SO(10) model where B-L symmetry is broken
by a {\bf 126} dimensional Higgs multiplet which also contributes to fermion
masses in conjunction with a {\bf 10} dimensional superfield. This minimal
Higgs choice provides a partial unification of neutrino flavor structure with
that of quarks and has been shown to predict all three neutrino mixing angles
and the solar mass splitting in agreement with observations, provided one uses
the type II seesaw formula for neutrino masses. In this paper we generalize
this analysis to include arbitrary CP phases in couplings and vevs. We find
that (i) the predictions for neutrino mixings are similar with as before and other parameters in a somewhat bigger range and (ii) that
to first order in the quark mixing parameter (the Cabibbo angle), the
leptonic mixing matrix is CP conserving. We also find that in the absence of
any higher dimensional contributions to fermion masses, the CKM phase is
different from that of the standard model implying that there must be new
contributions to quark CP violation from the supersymmetry breaking sector.
Inclusion of higher dimensional terms however allows the standard model CKM
phase to be maintained.Comment: 22 pages, 6 figure
Bounds of the mass of Z' and the neutral mixing angles in general SU(2)_L x SU(2)_R x U(1) models
We consider phenomenological constraints on the mass and the
two mixing angles and of the neutral sector in a very general
class of models using electroweak data. We
do not make any specific assumptions such as left-right symmetry or the Higgs
structure. The analysis of the neutral sector has the advantage that it has
relatively fewer parameters compared to the charged sector since the
Cabibbo-Kobayashi-Maskawa (CKM) matrix elements in the right-handed sector do
not enter into the analysis, hence the number of various possibilities from a
big parameter space is reduced. We utilize theoretical considerations on the
masses of the gauge particles and the mixing angles. We combine the precision
electroweak data from LEP I and the low-energy neutral-current experimental
data to constrain the parameters introduced in the model. It turns out that
GeV, with little constraint on
. In the left-right symmetric theory, should be
larger than 900 GeV. With these constraints, we compare the values for , and
at LEP II with experimental values.Comment: 34 pages, a LaTeX file with macros elsart and pictex. 4 Figure