A statistical approach for polarized parton distributions

A global next-to-leading order QCD analysis of unpolarized and polarized deep-inelastic scattering data is performed with parton distributions constructed in a statistical physical picture of the nucleon. The chiral properties of QCD lead to strong relations between quarks and antiquarks distributions and the importance of the Pauli exclusion principle is also emphasized. We obtain a good description, in a broad range of $x$ and $Q^2$, of all measured structure functions in terms of very few free parameters. We stress the fact that at RHIC-BNL the ratio of the unpolarized cross sections for the production of $W^+$ and $W^-$ in $pp$ collisions, will directly probe the behavior of the $\bar d(x) / \bar u(x)$ ratio for $x \geq 0.2$, a definite and important test for the statistical model. Finally, we give specific predictions for various helicity asymmetries for the $W^{\pm}, Z$ production in $pp$ collisions at high energies, which will be measured with forthcoming experiments at RHIC-BNL and are sensitive tests of the statistical model for $\Delta \bar u(x)$ and $\Delta \bar d(x)$.Comment: 49 pages, 27 eps figure

Neutrinoless double beta decay in SO(10) inspired seesaw models

By requiring the lower limit for the lightest right-handed neutrino mass, obtained in the baryogenesis from leptogenesis scenario, and a Dirac neutrino mass matrix similar to the up-quark mass matrix we predict small values for the $\nu_e$ mass and for the matrix element $m_{ee}$ responsible of the neutrinoless double beta decay, $m_{\nu_e}$ around $5\cdot10^{-3}$ eV and $m_{ee}$ smaller than $10^{-3}$ eV, respectively. The allowed range for the mass of the heaviest right-handed neutrino is centered around the value of the scale of B - L breaking in the SO(10) gauge theory with Pati-Salam intermediate symmetry.Comment: 9 pages, RevTex4. Revised, title change

Intermediate Symmetries in the Spontaneous Breaking of Supersymmetric SO(10)

We study the supersymmetric spontaneous symmetry breaking of SO(10) into SU(3)xSU(2)xU(1) for the most physically interesting cases of SU(5) or flipped SU(5)xU(1) intermediate symmetries. The first case is more easily realized while the second one requires a fine-tuning condition on the parameters of the superpotential. This is because in the case of SU(5) symmetry there is at most one singlet of the residual symmetry in each SO(10) irreducible representation. We also point out on more general grounds in supersymmetric GUT's that some intermediate symmetries can be exactly realized and others can only be approximated by fine-tuning. In the first category, there could occur some tunneling between the vacua with exact and approximate intermediate symmetry. The flipped SU(5)xU(1) symmetry improves the unification of gauge couplings if (B-L) is broken by (B-L)=1 scalars yielding right handed neutrino masses below 10^{14} GeV}.Comment: LaTex, 9 page

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 $F_2$ and $g_1$, both for proton and deuteron, in fair agreement with experimental data.Comment: 5 pages, in Latex, 3 figure

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

Recent tests for the statistical parton distributions

We compare some recent experimental results obtained at DESY, SLAC and Jefferson Lab., with the predictions of the statistical model, we have previously proposed. The result of this comparison is very satisfactory.Comment: 12 pages, 6 eps figures, version to appear in Mod. Phys. Lett.

Magnetic field computation in a physically large domain with thin metallic shields

A three-dimensional edge element procedure is presented to analyze the magnetic field around thin shields embedded in a physically large domain. The shield region is eliminated from the computational domain and coupled boundary conditions named impedance network boundary conditions are imposed on the new boundary surfaces to take into account the field discontinuity produced by the eliminated shield. An experimental setup is built and the measured magnetic fields are compared to the results obtained by the proposed procedure

Supernova Neutrino Energy Spectra and the MSW Effect

The distortions in the thermal energy spectra for neutrinos produced in a supernova when a resonant oscillation, MSW effect, occurs are determined. In order to show this effect for some relevant and representative examples of unified gauge models, we have chosen $SO(10)$, and $SU(5)_{SUSY}$, $SO(10)_{SUSY}$ with a particular scheme for fermion masses (DHR model). The analysis has been performed for two choices of neutrinos parameters, predicted by the above models, and capable to explain the solar neutrino problem. In both cases one observes a strong distortion in the electron neutrino energy spectrum. This effect, computed for a wide range of $SO(10)_{SUSY}$ models has produced the same results of the previous supersymmetric ones.Comment: 14 pages, plain LaTeX, 6 figures, revised version to be published in Z. Phys.

Finite-Element Analysis of Temperature Increase in Vascularized Biological Tissues Exposed to RF Sources

A new model of numerical dosimetry is proposed for RF exposure. First, the specific absorption rate (SAR) is computed. Then, the heat transfer governed by the bio-heat equation with convection term is numerically solved by a finite-element method (FEM) procedure considering the discrete vascular model of the perfused tissue. By some manipulations of the FEM equations and by generating an adequate FEM mesh, it is possible to solve the thermal convection in the blood vessels considering a one-dimensional domain embedded in the fully three-dimensional domain where only the thermal diffusion is analyzed