268 research outputs found
Leptogenesis within a generalized quark-lepton symmetry
Quark-lepton symmetry has been shown to be inconsistent with baryogenesis via
leptogenesis in natural schemes of the see-saw mechanism. Within the
phenomenological approach of textures, we relax this strict symmetry and
propose weaker conditions, namely models of the neutrino Dirac mass matrix
which have the same hierarchy as the matrix elements of . We call
this guide-line generalized quark-lepton symmetry. We consider
in detail particular cases in which the moduli of the matrix elements of
are equal to those of . Within the phenomenological approach of textures,
we try for the heavy Majorana mass matrix diagonal and off-diagonal forms. We
find that an ansatz for preserving the hierarchy, together with an
off-diagonal model for the heavy Majorana neutrino mass, is consistent with
neutrino masses, neutrino mixing and baryogenesis via leptogenesis for an
intermediate mass scale GeV. The preservation of the
hierarchical structure could come from a possible symmetry scheme.Comment: 12 pages, RevTex4. Title and abstract changed. Revised and enlarged
versio
A Positive Test for Fermi-Dirac Distributions of Quark-Partons
By describing a large class of deep inelastic processes with standard
parameterization for the different parton species, we check the characteristic
relationship dictated by Pauli principle: broader shapes for higher first
moments. Indeed, the ratios between the second and the first moment and the one
between the third and the second moment for the valence partons is an
increasing function of the first moment and agrees quantitatively with the
values found with Fermi-Dirac distributions.Comment: 15 pages LaTeX, 2 eps figures. Final version, to appear in Mod. Phys.
Lett.
Further experimental tests for simple relations between unpolarized and polarized quark parton distributions
Some simple relations between unpolarized and polarized quark parton
distributions have direct experimental consequences which will be presented
here. In particular, we will see that it is possible to relate the deep
inelastic structure functions and , both for proton and deuteron, in
fair agreement with experimental data.Comment: 5 pages, in Latex, 3 figure
Nonleptonic Cabibbo Favoured -Decays and -Asymmetries for Charmed Final Hadron States in Isgur and Wise Theory
The Cabibbo allowed non-leptonic -decays in two hadrons are studied,
within the factorization hypothesis, in the framework of Isgur and Wise theory
for the matrix elements of the weak currents. The
symmetry relates to currents, which
have been measured in the semileptonic strange decays of charmed particles. By
assuming colour screening and allowing for invariant contributions from
the annihilation terms with charmed final states one is able to comply with the
present experimental knowledge.\\ The violating asymmetries in neutral
decays are given for charmed final states in terms of the angles. With
the central values found for the annihilation parameters there is a destructive
(constructive) interference between the direct and annihilation terms in the
Cabibbo allowed (doubly forbidden) amplitudes for the decays into
and so that they may be of the same order.
This would imply large asymmetries, for which however our present knowledge on
the amplitudes does not allow to predict even their sign.\\ We have better
confidence in our predictions for the charged final states than the neutral
ones and can draw the conclusion that the detection of the corresponding
asymmetries requires, at least, tagged neutral -particles.Comment: CERNTEX, 17 pages, DSF-92/23, INFN-NA-IV-92/2
Polarized Quarks, Gluons and Sea in Nucleon Structure Functions
We perform a NLO analysis of polarized deep inelastic scattering data to test
two different solutions to the so called spin crisis: one of them based on the
axial gluon anomaly and consistent with the Bjorken sum rule and another one,
where the defects in the spin sum rules and in the Gottfried sum rule are
related. In this case a defect is also expected for the Bjorken sum rule. The
first solution is slightly favoured by the SLAC E154 results, but both options
seem to be consistent with the CERN SMC data.Comment: 19 pages, LateX, 6 figures. Figures included in the tex
Statistical Inspired Parton Distributions and the Violation of QPM Sum Rules
A quantum statistical parametrization of parton distributions has been
considered. In this framework, the exclusion Pauli principle connects the
violation of the Gottfried sum rule with the Ellis and Jaffe one, and implies a
defect in the Bjorken sum rule. However, in terms of standard parametrizations
of the polarized distributions a good description of the data is obtained once
a large gluon polarization is provided. Interestingly, in this description
there is no violation of the Bjorken sum rule.Comment: 10 pages, LateX + 15 figures, Talk given at ``Hadrons 96'' Workshop,
Novy Svet (CRIMEA), June 9-1
Low x Behaviour of the Isovector Nucleon Polarized Structure Function and the Bjorken Sum Rule
The combination g_1^p(x) - g_1^n(x) is derived from SLAC data on polarized
proton and deuteron targets, evaluated at Q^2 = 10 GeV^2, and compared with the
results of SMC experiment. The agreement is satisfactory except for the points
at the three lowest x, which have an important role in the SMC evaluation of
the l.h.s. of the Bjorken sum rule.Comment: 9 pages LaTeX + 4 eps figures, to appear in Modern Physics Letters
Octet Quark Contents from SU(3) Flavor Symmetry
With the parametrization of parton distribution functions (PDFs) of the
proton by Soffer \textit{et al.}, we extend the valence quark contents to other
octet baryons by utilizing SU(3) flavor symmetry. We find the method
practically useful. Fragmentation functions (FFs) are further obtained through
the phenomenological Gribov-Lipatov relation at the region. Our
results are compared with different models, and these different predictions can
be discriminated by upcoming experiments.Comment: 6 pages, 5 figures, final version for journal publicatio
CP violating asymmetries in charged D meson decays
The CP violating asymmetries for Cabibbo suppressed charged D meson decays in
the standard model are estimated in the factorized approximation, using the
two-loop effective hamiltonian and a model for final state interactions
previously tested for Cabibbo allowed D decays. No new parameters are added.
The predictions are larger than expected and not too far from the experimental
possibilities.Comment: 13 pages, Roma n. 91
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