Baryogenesis via leptogenesis in SO(10) models

We discuss the baryogenesis via leptogenesis mechanism within the supersymmetric and nonsupersymmetric SO(10) models. We find that the nonsupersymmetric model, endowed with an intermediate scale, is generally favoured, unless some fine tuning occurs in the supersymmetric case.Comment: 9 pages, RevTex, with 1 figur

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

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

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 $M_D$ which have the same hierarchy as the matrix elements of $M_u$. We call this guide-line generalized $hierarchical$ quark-lepton symmetry. We consider in detail particular cases in which the moduli of the matrix elements of $M_D$ are equal to those of $M_u$. 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 $M_D$ 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 $m_R \sim 10^{12}$ 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

Bounds for the mass of the heaviest right-handed neutrino in SO(10) theories

By relating the Dirac neutrino mass matrix to the mass of the charged fermions and assuming that the product of the masses of the two lightest left-handed neutrinos is of the order of $\Delta m^2_{sol}$, we derive, within a leptogenesis scenario, a range of values for the mass of the heaviest right-handed neutrino, centered around the scale of $B-L$ symmetry breaking in the SO(10) theory with Pati-Salam intermediate symmetry.Comment: 7 pages, RevTex4. Few correction

Neutrino masses and mixings in SO(10)

Assuming a Zee-like matrix for the right-handed neutrino Majorana masses in the see-saw mechanism, one gets maximal mixing for vacuum solar oscillations, a very small value for $U_{e3}$ and an approximate degeneracy for the two lower neutrino masses. The scale of right-handed neutrino Majorana masses is in good agreement with the value expected in a SO(10) model with Pati-Salam SU(4)\ts SU(2)\ts SU(2) intermediate symmetry.Comment: 11 pages, no figures. References adde

Nonleptonic Cabibbo Favoured BB-Decays and CPCP-Asymmetries for Charmed Final Hadron States in Isgur and Wise Theory

The Cabibbo allowed non-leptonic $B$-decays in two hadrons are studied, within the factorization hypothesis, in the framework of Isgur and Wise theory for the matrix elements of the $\Delta B=-\Delta C=\pm 1$ weak currents. The $SU(2)_{HF}$ symmetry relates $|\Delta B|=1$ to $|\Delta C|=1$ currents, which have been measured in the semileptonic strange decays of charmed particles. By assuming colour screening and allowing for $SU(3)$ invariant contributions from the annihilation terms with charmed final states one is able to comply with the present experimental knowledge.\\ The $CP$ violating asymmetries in neutral $B$ decays are given for charmed final states in terms of the $K-M$ 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 $D^{0}(D^{*0})\pi^0$ and $D^0\rho^0$ 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, $10^6$ tagged neutral $B$-particles.Comment: CERNTEX, 17 pages, DSF-92/23, INFN-NA-IV-92/2

Quantum Effects in Friedmann-Robertson-Walker Cosmologies

Electrodynamics for self-interacting scalar fields in spatially flat Friedmann-Robertson-Walker space-times is studied. The corresponding one-loop field equation for the expectation value of the complex scalar field in the conformal vacuum is derived. For exponentially expanding universes, the equations for the Bogoliubov coefficients describing the coupling of the scalar field to gravity are solved numerically. They yield a non-local correction to the Coleman-Weinberg effective potential which does not modify the pattern of minima found in static de Sitter space. Such a correction contains a dissipative term which, accounting for the decay of the classical configuration in scalar field quanta, may be relevant for the reheating stage. The physical meaning of the non-local term in the semiclassical field equation is investigated by evaluating this contribution for various background field configurations.Comment: 17 pages, plain TeX + 5 uuencoded figure