217 research outputs found
Quasi degenerate Neutrino Masses with Universal Strength Yukawa Couplings
A simple ansatz is proposed for neutrino and charged lepton mass matrices,
within the framework of universal strength for Yukawa couplings. In this
framework all Yukawa couplings have equal moduli and the flavour dependence is
only in their phases. We take into account the solar neutrino deficit and the
atmospheric neutrino anomaly, assuming three neutrino families only. The ansatz
leads in a natural way to small mixing involving neutrinos of quasi degenerate
masses, as required to explain the solar neutrino deficit in the nonadiabatic
MSW solution, while having the large mixing necessary to explain the
atmospheric neutrino anomaly.Comment: 10 pages, LATEX, no special macros, no figures, no table
A Real CKM Matrix and Physics Beyond the Standard Model
We study the possible existence of a real Cabibbo-Kobayashi-Maskawa (CKM)
matrix, with CP violation originating from physics beyond the standard model
(SM). We show that present experimental data allow for a real CKM matrix
provided that new physics also contributes to Delta m_{B_d} by at least 20% of
the SM contribution (for rho > 0), besides generating CP violation in the kaon
sector. The naturalness of a real CKM matrix is studied within the framework of
general multi-Higgs-doublet models with spontaneous CP violation. As an
example, we discuss a specific two-Higgs-doublet model and its implications for
CP asymmetries in non-leptonic neutral B-meson decays.Comment: 19 pages, LaTeX2e, 1 figure, uses amssymb, elsart, psfig, and subeqn
style file
A relation between CP violation of low energy and leptogenesis
We discuss how CP violation generating lepton number asymmetry can be related
to CP violation in low energy.Comment: A poster Talk presented at KEKTC5, submitted to the proceeding
Yukawa Structure with Maximal Predictability
A simple Ansatz for the quark mass matrices is considered, based on the
assumption of a power structure for the matrix elements and the requirement of
maximal predictability. A good fit to the present experimental data is obtained
and the position of the vertex of the unitarity triangle, i.e.
(\bar{\rho},\bar{\eta}), is predicted.Comment: 13 pages, 2 EPS figures, some modifications and references added;
version to appear in Phys. Lett.
Spontaneous CP Violation in a SUSY Model with a complex CKM
It is pointed out that the recent measurement of the angle of the
unitarity triangle, providing irrefutable evidence for a complex
Cabibbo-Kobayashi-Maskawa (CKM) matrix, presents a great challenge for
supersymmetric models with spontaneous CP violation. We construct a new minimal
extension of the minimal supersymmetric standard model (MSSM), with spontaneous
CP breaking, which leads to a complex CKM matrix, thus conforming to present
experimental data. This is achieved through the introduction of two singlet
chiral superfields and a vector-like quark chiral superfield which mixes with
the standard quarks. A symmetry is introduced in order to have a
potential solution to the strong CP problem.Comment: 12 pages. Uses the elsart.cls LaTeX class. Minor corrections and
references adde
Complex CKM from Spontaneous CP Violation Without Flavor Changing Neutral Current
We analyse the general constraints on unified gauge models with spontaneous
CP breaking that satisfy the conditions that (i) CP violation in the quark
sector is described by a realistic complex CKM matrix, and (ii) there is no
significant flavor changing neutral current effects in the quark sector. We
show that the crucial requirement in order to conform to the above conditions
is that spontaneous CP breaking occurs at a very high scale by complex vevs of
standard model singlet Higgs fields. Two classes of models are found, one
consisting of pure Higgs extensions and the other one involving fermionic
extensions of the standard model. We give examples of each class and discuss
their possible embeddings into higher unified theories. One of the models has
the interesting property that spontaneous CP violation is triggered by
spontaneous P violation, thereby linking the scale of CP violation to the
seesaw scale for neutrino masses.Comment: Latex file ; 18 pages; No figures; some typos correcte
Relating the scalar flavour-changing neutral couplings to the CKM matrix
We build a class of two-Higgs-doublet models in which the flavour-changing
couplings of the neutral scalars are related in an exact way to elements of the
quark mixing matrix. In this framework, we explore the different possibilities
for CP violation and find some interesting scenarios, like a realization of the
superweak idea without CP violation in the -meson system. In another
scenario the neutral scalars can be relatively light, and their contributions
to the -- transitions can alter the standard-model predictions
for CP violation in that system.Comment: 12 pages LATEX, no figure
Large effects on \BsBs mixing by vector-like quarks
We calculate the contributions of the vector-like quark model to \BsBs
mixing, taking into account the constraints from the decay . In
this model the neutral bosons mediate flavor-changing interactions at the tree
level. However, \BsBs mixing is dominated by contributions from the box
diagrams with the top quark and the extra up-type quark. In sizable ranges of
the model parameters, the mixing parameter is much different from the
standard model prediction.Comment: 11 pages, 4 figures, To be published in Phys. Rev.
The Problem of Large Leptonic Mixing
Unlike in the quark sector where simple permutation symmetries can
generate the general features of quark masses and mixings, we find it
impossible (under conditions of hierarchy for the charged leptons and without
considering the see-saw mechanism or a more elaborate extension of the SM) to
guarantee large leptonic mixing angles with any general symmetry or
transformation of only known particles. If such symmetries exist, they must be
realized in more extended scenarios.Comment: RevTeX, 4 pages, no figure
Dynamical CP Violation and Flavour-Changing Processes
We investigate the phenomenological constraints on a model where, besides the
standard model Higgs sector, there is an effective new strong interaction
acting on the third generation of quarks and characterized by a -like
term. This term induces electroweak symmetry breaking and leads to
dynamical spontaneous CP violation. We show that the constraints coming from K
physics and the electric dipole moment of the neutron impose that the new
physics scale should be of the order of 35 TeV. Contrary to naive expectations,
the predictions of the model for B physics are very close to the standard model
ones. The main differences appear in processes involving the up quarks such as
mixing and in the electric dipole moment of the neutron, which
should be close to the experimental limit. Possible deviations from the
standard model predictions for CP asymmetries in B decays are also considered.Comment: LaTeX, 25 pages, 4 figure
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