66 research outputs found
Supersymmetric SO(10) for fermion masses and mixings: rank-1 structures of flavour
We consider a supersymmetric SO(10) model with a SU(3) symmetry of flavour in
which fermion masses emerge via the see-saw mixing with superheavy fermions in
16+16bar representations. In this model the dangerous D=5 operators of proton
decay are naturally suppressed and flavour-changing supersymmetric effects are
under control. The mass matrices for all fermion types (up and down quarks,
charged leptons as well as neutrinos) appear in the form of combinations of
three rank-1 matrices, common to all types of fermions, with different
coefficients that are successive powers of small parameters, related to each
other by SO(10) symmetry properties. Two versions of the model are considered,
in which approximate grand unification of masses takes place between quarks and
leptons of the first family (with very small \tan\beta) or for the ones of the
second family (predicting moderate \tan\beta ~ 7-8). The second version
exhibits an interesting mechanism of unification of the determinants of the
Yukawa matrices of all types of fermions at the GUT scale and it provides a
perfect fit of the known data for fermion masses, mixing and CP-violation. It
predicts a hierarchical pattern of neutrino masses with non-zero theta_e3,
within 2-7 degrees. In addition, it predicts the correct sign of the baryon
asymmetry of the Universe via the leptogenesys scenario.Comment: 30 Pages, 3 figures. Clarified comments on neutrino scales and on
universal seesaw, updated references. Version appeared on JHE
Soft SUSY breaking contributions to proton decay
We show that in supersymmetric grand unified theories new effective D=4 and
D=5 operators for proton decay are induced by soft SUSY-breaking terms, when
heavy GUT gauge bosons are integrated out, in addition to the standard D=6
ones. As a result, the proton lifetime in gauge mediated channels can be
enhanced or even suppressed depending on the size of the heavy Higgses soft
terms.Comment: 16 pages, 2 figures, LaTeX, JHEP3 class, axodra
Mirror World, Supersymmetric Axion and Gamma Ray Bursts
A modification of the relation between axion mass and the PQ constant permits
a relaxation of the astrophysical constraints, considerably enlarging the
allowed axion parameter space. We develop this idea in this paper, discussing a
model for an {\it ultramassive} axion, which essentially represents a
supersymmetric Weinberg-Wilczek axion of the mirror world. The experimental and
astrophysical limits allow a PQ scale f_a ~ 10^4-10^6 GeV and a mass m_a ~
1MeV, which can be accessible for future experiments.
On a phenomenological ground, such an {\it ultramassive} axion turns out to
be quite interesting. It can be produced during the gravitational collapse or
during the merging of two compact objects, and its subsequent decay into e+e-
provides an efficient mechanism for the transfer of the gravitational energy of
the collapsing system to the electron-positron plasma. This could resolve the
energy budget problem in the Gamma Ray Bursts and also help in understanding
the SN type II explosion phenomena.Comment: 20 pages, 5 eps figures, added footnote and reference
Seesaw Mass Matrix Model of Quarks and Leptons with Flavor-Triplet Higgs Scalars
In a seesaw mass matrix model M_f = m_L M_F^{-1} m_R^\dagger with a universal
structure of m_L \propto m_R, as the origin of m_L (m_R) for quarks and eptons,
flavor-triplet Higgs scalars whose vacuum expectation values v_i are
proportional to the square roots of the charged lepton masses m_{ei}, i.e. v_i
\propto \sqrt{m_{ei}}, are assumed. Then, it is investigated whether such a
model can explain the observed neutrino masses and mixings (and also quark
masses and mixings) or not.Comment: version accepted by EPJ
Masses of Fermions in Supersymmetric Models
We consider the mass generation for the usual quarks and leptons in some
supersymmetric models. The masses of the top, the bottom, the charm, the tau
and the muon are given at the tree level. All the other quarks and the electron
get their masses at the one loop level in the Minimal Supersymmetric Standard
Model (MSSM) and in two Supersymmetric Left-Right Models, one model uses
triplets (SUSYLRT) to break -symmetry and the other use
doublets(SUSYLRD).Comment: 24 pages, 2 figures and 3 table
Neutrino and axion hot dark matter bounds after WMAP-7
We update cosmological hot dark matter constraints on neutrinos and hadronic
axions. Our most restrictive limits use 7-year data from the Wilkinson
Microwave Anisotropy Probe for the cosmic microwave background anisotropies,
the halo power spectrum (HPS) from the 7th data release of the Sloan Digital
Sky Survey, and the Hubble constant from Hubble Space Telescope observations.
We find 95% C.L. upper limits of \sum m_\nu<0.44 eV (no axions), m_a<0.91 eV
(assuming \sum m_\nu=0), and \sum m_\nu<0.41 eV and m_a<0.72 eV for two hot
dark matter components after marginalising over the respective other mass. CMB
data alone yield \sum m_\nu<1.19 eV (no axions), while for axions the HPS is
crucial for deriving m_a constraints. This difference can be traced to the fact
that for a given hot dark matter fraction axions are much more massive than
neutrinos.Comment: 9 pages, 3 figures, uses iopart.cls; v2: one additional figure,
references added, version accepted by JCA
Large Lepton Mixings from Continuous Symmetries
Within the broad context of quark-lepton unification, we investigate the
implications of broken continuous family symmetries which result from requiring
that in the limit of exact symmetry, the Dirac mass matrices yield hierarchical
masses for the quarks and charged leptons, but lead to degenerate light
neutrino masses as a consequence of the seesaw mechanism, without requiring
hierarchical right-handed neutrino mass terms. Quark mixing is then naturally
small and proportional to the size of the perturbation, but lepton mixing is
large as a result of degenerate perturbation theory, shifted from maximal
mixing by the size of the perturbation. Within this approach, we study an
illustrative two-family prototype model with an SO(2) family symmetry, and
discuss extensions to three-family models.Comment: 23 page
Asymmetric Inflationary Reheating and the Nature of Mirror Universe
The existence of a shadow world (or mirror universe) with matter and forces
identical to that of the visible world but interacting with the latter only via
gravity can be motivated by superstring theories as well as by recent attempts
to understand the nature of a sterile neutrino needed if all known neutrino
data are to be consistent with each other. A simple way to reconcile the
constraints of big bang nucleosynthesis in such a theory is to postulate that
the reheating temperature after inflation in the mirror universe is lower than
that in the visible one. We have constructed explicit models that realize this
proposal and have shown that the asymmetric reheating can be related to a
difference of the electroweak symmetry breaking scales in the two sectors,
which is needed for a solution of the neutrino puzzles in this picture.
Cosmological implications of the mirror matter are also discussed.Comment: 13 pages, LATEX, no figures (slight textual changes, few references
added
Hierarchical Neutrino Mass Matrices, CP violation and Leptogenesis
In this work we study examples of hierarchical neutrino mass matrices
inspired by family symmetries, compatible with experiments on neutrino
oscillations, and for which there is a connection among the low energy CP
violation phase associated to neutrino oscillations, the phases appearing in
the amplitude of neutrinoless double beta decay, and the phases relevant for
leptogenesis. In particular, we determine the predictions from a texture based
on an underlying SU(3) family symmetry together with a GUT symmetry, and a
strong hierarchy for the masses of the heavy right handed Majorana masses. We
also give some examples of inverted hierarchies of neutrino masses, which may
be motivated in the context of U(1) family symmetries.Comment: 34 pages. Replaced with published version -typos, corrections and
references adde
Evolution of the Yukawa coupling constants and seesaw operators in the universal seesaw model
The general features of the evolution of the Yukawa coupling constants and
seesaw operators in the universal seesaw model with det M_F=0 are investigated.
Especially, it is checked whether the model causes bursts of Yukawa coupling
constants, because in the model not only the magnitude of the Yukawa coupling
constant (Y_L^u)_{33} in the up-quark sector but also that of (Y_L^d)_{33} in
the down-quark sector is of the order of one, i.e., (Y_L^u)_{33} \sim
(Y_L^d)_{33} \sim 1. The requirement that the model should be calculable
perturbatively puts some constraints on the values of the intermediate mass
scales and tan\beta (in the SUSY model).Comment: 21 pages, RevTex, 10 figure
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