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F. Buccella

Publications and source records attributed to F. Buccella.

At least 37 records · Page 2Linked to original sources
arXiv2000

SO(10)-Inspired See-Saw Mechanism

We determine the nu_{R} Majorana mass matrix from the experimental data on neutrino oscillations in the framework of a see-saw SO(10) model, where we impose the condition (M^R)_{33} = 0 to avoid too large fine-tunings in the see-saw formula. We find a class of solutions with the two lowest neutrino masses almost degenerate and the scale of the matrix elements of M^R in the range 10^{11} -10^{12} GeV in agreement with Pati-Salam intermediate symmetry. We find also solutions with smaller neutrino masses, for which the scale of M_R depends on the solution to the "solar neutrino problem" and on the value of the component of ν_e along the highest mass eigenstate, U_{e3}.

hep-ph↗
arXiv2000

Solutions of D_α- 0 from Homogeneous Invariant Functions

We prove that the existence of a homogeneous invariant of degree n for a representation of a semi-simple Lie group guarantees the existence of non-trivial solutions of D_α = 0: these correspond to the maximum value of the square of the invariant divided by the norm of the representation to the n^{th} power.

math-ph↗
arXiv2000

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.

hep-ph↗
arXiv2000

The Strange Quark Problem in the Framework of Statistical Distributions

A large class of polarized and unpolarized deep inelastic data is successfully described with Fermi-Dirac functions for the non-diffractive part of quark parton distributions. The NLO approach used here improves the agreement with experiment of the previous LO work. We get a broader distribution for the strange parton s(x) than for sbar(x).

hep-ph↗
arXiv1999

Neutrino Masses in SO(10) Theories

We review the status of a class of gauge unified models based on SO(10) group and discuss the main phenomenological implications of these models in particular for neutrino masses.

hep-ph↗
arXiv1998

Quarks and Gluons in Nucleon Polarized Structure Functions

We study the available data in polarized e-p deep inelastic scattering 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. Experimental data, especially the very recent SLAC E154, favour the first solution and demand a gluon polarization $ΔG = 2.25 \pm 1.39$.

hep-ph↗
arXiv1998

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.

hep-ph↗
arXiv1998

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.

hep-ph↗
arXiv1997

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.

hep-ph↗
arXiv1997

Neutrino masses and baryogenesis in SO(10) unified theories

We report on some phenomenological implications of a class of unified models based on SO(10) gauge group, with intermediate symmetry group containing SU(2)_R. Interesting predictions for neutrino masses are discussed, which are relevant both for solar neutrino and dark matter problems, as well as a model for the formation of the baryon asymmetry of the universe required by primordial nucleosynthesis.

hep-ph↗
arXiv1996

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.

hep-ph↗
arXiv1996

Quantum Statistical Parton Distributions and the Spin Crisis

Quantum statistical distributions for the partons provide a fair description of deep inelastic scattering data at $Q^2 = 3$ and $10 (GeV/c)^2$. The study of the polarized structure functions seems to suggest an alternative possible solution of the {\it spin crisis} based on the Pauli principle. In this scheme, in fact, the defects of the Gottfried sum rule and Ellis--Jaffe sum rule for proton, result strongly connected. This possibility finds particular evidence from the phenomenological observation that the relation $Δu = 2 \tilde{F} + u - d -1$ seems well satisfied by parton distributions.

hep-ph↗
arXiv1996

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.

hep-ph↗
arXiv1996

Charm nonleptonic decays and final state interactions

A global previous analysis of two-body nonleptonic decays of $D$ mesons has been extended to the decays involving light scalar mesons. The allowance for final state interaction also in nonresonant channels provides a fit of much improved quality and with less symmetry breaking in the axial charges. We give predictions for about 50 decay branching ratios yet to be measured. We also discuss long distance contributions to the difference $ΔΓ$ between the $D_S$ and $D_L$ widths.

hep-ph↗
arXiv1995

Uncertainties on the CP Phase $\bfalpha$ due to Penguin Diagrams

A major problem in the determination of the the CP angle $α$, that should be measured through modes of the type $B_d, \bar{B}_d \to ππ, \cdots ,$ is the uncertainty coming from Penguin diagrams. We consider the different ground state modes $ππ$, $πρ$, $ρρ$, and, assuming the FSI phases to be negligible, we investigate the amount of uncertainty coming from Penguins that can be parametrized by a dilution factor $D$ and an angle shift $Δα$. The parameter $D$ is either 1 or very close to 1 in all these modes, and it can be measured independently, up to a sign ambiguity, by the $t$ dependence. Assuming factorization, we show that $Δα$ is much smaller for the modes $ρπ$ and $ρρ$ than for $ππ$, and we plot their allowed region as a function of $α$ itself. Moreover, we show that most of the modes contribute to the asymmetry with the same sign, and define for their sum an effective $D_{eff}$ and an effective $Δα_{eff}$, an average of $Δα$ for the different modes. It turns out that $D_{eff}$ is of the order of 0.9, $Δα_{eff}$ is between 5 $\%$ and 10 $\%$ and, relative to $ππ$, the statistical gain for the sum is of about a factor 10. Finally, we compute the ratios $Kπ/ππ, \cdots$ that test the strength of the Penguins and depend on the CP angles, as emphasized by Silva and Wolfenstein and by Deandrea et al.

hep-ph↗
arXiv1995

Fermi-Dirac statistics plus liquid description of quark partons

A previous approach with Fermi-Dirac distributions for fermion partons is here improved to comply with the expected low $x$ behaviour of structure functions. We are so able to get a fair description of the unpolarized and polarized structure functions of the nucleons as well as of neutrino data. We cannot reach definite conclusions, but confirm our suspicion of a relationship between the defects in Gottfried and spin sum rules.

hep-ph↗