10,554 research outputs found
Fermion Mass Matrices in term of the Cabibbo-Kobayashi-Maskawa Matrix and Mass Eigenvalues
A parameter free, model independent analysis of quark mass matrices is
carried out. We find a representation in terms of a diagonal mass matrix for
the down (up) quarks and a suitable matrix for the up (down) quarks, such that
the mass parameters only depend on the six quark masses and the three angles
and phase appearing in the Cabibbo-Kobayashi-Maskawa matrix. The results found
may also be applied to the Dirac mass matrices of the leptons.Comment: 7 pages LaTeX, no figures. Title changed, Particle Data Group
parametrization of CKM matrix used in equation (8), numerical values in table
1 evaluated using the quark mass values at the Z^o mass scale, equation (21)
eliminated and 2 references change
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.
A self-consistent test of Comptonization models using a long BeppoSAX observation of NGC 5548
We test accurate models of Comptonization spectra over the high quality data
of the BeppoSAX long look at NGC 5548. The data are well represented by a plane
parallel corona with an inclination angle of 30, a soft photon
temperature of 5 eV and a hot plasma temperature and optical depth of 360 keV and 0.1, respectively. If energy balance
applies, such values suggest that a more ``photon-starved'' geometry (e.g. a
hemispheric region) is necessary. The spectral softening detected during a
flare, appears to be associated to a decrease of the heating-to-cooling ratio,
indicating a geometric and/or energetic modification of the disk plus corona
system. The hot plasma temperature derived with the models above is
significantly higher than that obtained fitting the same data with a power law
plus high energy cut off model for the continuum. This is due to the fact that
in anisotropic geometries Comptonization spectra show "intrinsic" curvature
which moves the fitted high energy cut-off to higher energies.Comment: 4 pages, 2 figures, to appear in the proceedings of the conference
"X-ray Astronomy '99", Bologna, Italy, September 199
SO(10) Unified Theories and Cosmology
We review the status of a class of gauge unified models based on SO(10)
group. After a pedagogical introduction to SO(10) gauge theories, we discuss
the main phenomenological implications of these models. The upper limit on
proton lifetime are obtained and the prediction for neutrino masses are
compared with the astrophysical and cosmological constraints coming from solar
neutrino data and dark matter problem. Possible scenarios for the production of
the baryon asymmetry of the universe required by primordial nucleosynthesis are
also discussed.Comment: 16 pages LaTeX, no figures, needs sprocl.sty, included. To appear in
the proceedings of NANP97, Dubna, July 1997. Few misprints correcte
Scaling of variables and the relation between noncommutative parameters in Noncommutative Quantum Mechanics
We consider Noncommutative Quantum Mechanics with phase space
noncommutativity. In particular, we show that a scaling of variables leaves the
noncommutative algebra invariant, so that only the self-consistent effective
parameters of the model are physically relevant. We also discuss the recently
proposed relation of direct proportionality between the noncommutative
parameters, showing that it has a limited applicability.Comment: Revtex4, 4 pages; version to match the published on
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