382 research outputs found
Fermion Masses and Mixings in the Little Flavon Model
We present a complete analysis of the fermion masses and mixing matrices in
the framework of the little flavon model. In this model textures are generated
by coupling the fermions to scalar fields, the little flavons, that are
pseudo-Goldstone bosons of the breaking of a global SU(6) symmetry. The Yukawa
couplings arise from the vacuum expectation values of the flavon fields, their
sizes controlled by a potential a la Coleman-Weinberg. Quark and lepton mass
hierarchies and mixing angles are accomodated within the effective approach in
a natural manner.Comment: 11 pages, RevTeX4, version to appear on Phys. Rev.
The little flavons
Fermion masses and mixing matrices can be described in terms of spontaneously
broken (global or gauge) flavor symmetries. We propose a little-Higgs inspired
scenario in which an SU(2)xU(1) gauge flavor symmetry is spontaneously (and
completely) broken by the vacuum of the dynamically induced potential for two
scalar doublets (the flavons) which are pseudo-Goldstone bosons remaining after
the spontaneous breaking--at a scale between 10 and 100 TeV--of an approximate
SU(6) global symmetry. The vacuum expectation values of the flavons give rise
to the texture in the fermion mass matrices. We discuss in detail the case of
leptons. Light-neutrino masses arise by means of a see-saw-like mechanism that
takes place at the same scale at which the SU(6) global symmetry is broken. We
show that without any fine tuning of the parameters the experimental values of
the charged-lepton masses,the neutrino square mass differences and the
Pontecorvo-Maki-Nakagawa-Sakata mixing matrix are reproduced.Comment: 13 pages, revTeX4. Version to be published in PR
Parity nonconservation in deuteron photoreactions
We calculate the asymmetries in parity nonconserving deuteron
photodisintegration due to circularly polarized photons gamma+d to n+p with the
photon laboratory energy ranging from the threshold up to 10 MeV and the
radiative capture of thermal polarized neutrons by protons n+p to gamma+d. We
use the leading order electromagnetic Hamiltonian neglecting the smaller
nuclear exchange currents. Comparative calculations are done by using the
Reid93 and Argonne v18 potentials for the strong interaction and the DDH and
FCDH "best" values for the weak couplings in a weak one-meson exchange
potential. A weak NDelta transition potential is used to incorporate also the
Delta(1232)-isobar excitation in the coupled-channels formalism.Comment: 14 pages, 13 figures (18 eps files), LaTeX2
Parity nonconserving cold neutron-parahydrogen interactions
Three pion dominated observables of the parity nonconserving interactions
between the cold neutrons and parahydrogen are calculated. The transversely
polarized neutron spin rotation, unpolarized neutron longitudinal polarization,
and photon-asymmetry of the radiative polarized neutron capture are considered.
For the numerical evaluation of the observables, the strong interactions are
taken into account by the Reid93 potential and the parity nonconserving
interactions by the DDH model along with the two-pion exchange.Comment: 17 pages, 2 figure
Electroweak Radiative Corrections to Parity-Violating Electroexcitation of the
We analyze the degree to which parity-violating (PV) electroexcitation of the
resonance may be used to extract the weak neutral axial vector
transition form factors. We find that the axial vector electroweak radiative
corrections are large and theoretically uncertain, thereby modifying the
nominal interpretation of the PV asymmetry in terms of the weak neutral form
factors. We also show that, in contrast to the situation for elastic electron
scattering, the axial PV asymmetry does not vanish at the photon
point as a consequence of a new term entering the radiative corrections. We
argue that an experimental determination of these radiative corrections would
be of interest for hadron structure theory, possibly shedding light on the
violation of Hara's theorem in weak, radiative hyperon decays.Comment: RevTex, 76 page
Stability and collapse of localized solutions of the controlled three-dimensional Gross-Pitaevskii equation
On the basis of recent investigations, a newly developed analytical procedure
is used for constructing a wide class of localized solutions of the controlled
three-dimensional (3D) Gross-Pitaevskii equation (GPE) that governs the
dynamics of Bose-Einstein condensates (BECs). The controlled 3D GPE is
decomposed into a two-dimensional (2D) linear Schr\"{o}dinger equation and a
one-dimensional (1D) nonlinear Schr\"{o}dinger equation, constrained by a
variational condition for the controlling potential. Then, the above class of
localized solutions are constructed as the product of the solutions of the
transverse and longitudinal equations. On the basis of these exact 3D
analytical solutions, a stability analysis is carried out, focusing our
attention on the physical conditions for having collapsing or non-collapsing
solutions.Comment: 21 pages, 14 figure
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