arXiv subjects

F. Buccella

Publications and source records attributed to F. Buccella.

At least 19 recordsLinked to original sources

arXiv2025

Possible Explanation of $F_2^n/F_2^p$ at Large $x$ Using Quantum Statistical Mechanics

The recent accurate measurements of the scattering of electrons off of the mirror nuclei $^3$H and $^3$He show with small errors that the neutron to proton ratio $r(x)=F^n_2(x)/F^p_2(x)$, approaches a value larger than 1/4 for $x \to 1$. We suggest a possible explanation for this experimental result by studying the consequences of the Pauli exclusion principle for the parton distribution when the ratio is described by quantum statistical mechanics description in terms of three parameters inspired by the quantum statistical approach.

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arXiv2017

A neutrino mass-mixing sum rule from SO(10) and neutrinoless double beta decay

Minimal SO(10) grand unified models provide phenomenological predictions for neutrino mass patterns and mixing. These are the outcome of the interplay of several features, namely: i) the seesaw mechanism; ii) the presence of an intermediate scale where B-L gauge symmetry is broken and the right-handed neutrinos acquire a Majorana mass; iii) a symmetric Dirac neutrino mass matrix whose pattern is close to the up-type quark one. In this framework two natural characteristics emerge. Normal neutrino mass hierarchy is the only allowed, and there is an approximate relation involving both light-neutrino masses and mixing parameters. This differs from what occurring when horizontal flavour symmetries are invoked. In this case, in fact, neutrino mixing or mass relations have been separately obtained in literature. In this paper we discuss an example of such comprehensive mixing-mass relation in a specific realization of SO(10) and, in particular, analyse its impact on the expected neutrinoless double beta decay effective mass parameter $\langle m_{ee} \rangle$, and on the neutrino mass scale. Remarkably a lower limit for the lightest neutrino mass is obtained ($m_{\rm lightest} \gtrsim 7.5 \times 10^{-4}$ eV, at 3 $σ$ level).

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arXiv2012

Neutrino masses and proton decay in SO(10)

We consider the constraints on SO(10) unified models coming from the lower limits on proton lifetime and on the scale of B-L symmetry breaking within the framework of the seesaw model for neutrino masses. By upgrading a triangular relationship for the inverse of Majorana masses to the experimental situation with non maximal 2-3 mixing and non vanishing 1-3 mixing, we get for the sum of neutrino masses the upper limit 0.16 eV.

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arXiv2012

Seesaw model in SO(10) with an upper limit on right-handed neutrino masses

In the framework of SO(10) gauge unification and the seesaw mechanism, we show that the upper bound on the mass of the heaviest right-handed neutrino $M_{R_3} < 3 \times 10^{11}$ GeV, given by the Pati-Salam intermediate scale of $B-L$ spontaneous symmetry breaking, constrains the observables related to the left-handed light neutrino mass matrix. We assume such an upper limit on the masses of right-handed neutrinos and, as a first approximation, a Cabibbo form for the matrix $V^L$ that diagonalizes the Dirac neutrino matrix $m_D$. Using the inverse seesaw formula, we show that our hypotheses imply a triangular relation in the complex plane of the light neutrino masses with the Majorana phases. We obtain normal hierarchy with an absolute scale for the light neutrino spectrum. Two regions are allowed for the lightest neutrino mass $m_1$ and for the Majorana phases, implying predictions for the neutrino mass measured in Tritium decay and for the double beta decay effective mass $| |$.

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arXiv2011

Baryogenesis via leptogenesis from quark-lepton symmetry\par and a compact heavy $N_R$ spectrum

By demanding a compact spectrum for the right-handed neutrinos and an approximate quark-lepton symmetry inspired from SO(10) gauge unification (assuming a Dirac neutrino mass matrix close to the up quark mass matrix), we construct a {\it fine tuning} scenario for baryogenesis via leptogenesis. We find two solutions with a normal hierarchy, with the lightest neutrino mass $m_1$ different from zero, providing an absolute scale for the spectrum. In the approximations of the model, there are three independent CP phases : $δ_L$ (that we take of the order of the quark Kobayashi-Maskawa phase) and the two light neutrino Majorana phases $α$ and $β$. A main conclusion is that, although this general scheme is rather flexible, in some regions of parameter space we find that the necessary baryogenesis with its sign is given in terms of the $δ_L$ phase alone. The light Majorana phases can also be computed and turn out to be close of $π/2$ or small. Moreover, SO(10) breaks down to the Pati-Salam group $SU(4) \times SU(2) \times SU(2)$ at the expected natural intermediate scale of about $10^{10}-10^{11}\ GeV$. A prediction is done for the effective mass in $(ββ)_{0ν}$ decay, the $ν_e$ mass and the sum of all light neutrino masses.

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arXiv2009

How is transversity related to helicity for quarks and antiquarks inside the proton?

We consider the quark and antiquark transversity distributions inside a polarized proton and we study how they are expected to be related to the corresponding helicity distributions, both in sign and magnitude. Our considerations lead to simple predictions in good agreement with their first determination for light quarks from experimental data. We also give our predictions for the light antiquarks transversity distributions, so far unknown.

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arXiv2008

Spectrum of positive and negative parity pentaquarks, including $SU(3)_F$ breaking

We present the spectrum of the lightest pentaquark states of both parities and compare it with the present experimental evidence for these states. We have assumed that the main role for their mass splittings is played by the chromo-magnetic interaction. We have also kept into account the $SU(3)_F$ breaking for their contribution and for the spin orbit term. The resulting pattern is in good agreement with experiment.

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arXiv2007

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.

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arXiv2005

Spectrum of the Y=2 Pentaquarks

By assuming a mass formula for the spectrum of the Y=2 pentaquarks, where the chromo-magnetic interaction plays a main role, and identifying the lightest state with the Theta^+(1540), we predict a spectrum in good agreement with the few I=0 and I=1 candidates proposed in the past.

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arXiv2005

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 $ν_e$ mass and for the matrix element $m_{ee}$ responsible of the neutrinoless double beta decay, $m_{ν_e}$ 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.

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arXiv2004

A Selection Rule for Multiquark Decays

By assuming SU(6)_cs symmetry for pentaquark decays one finds a selection rule, which strongly reduces the number of states able to decay into a baryon and a meson final state and allows an intriguing identification for the Theta^+ particle recently discovered with the prediction of a narrow width.

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arXiv2004

Narrow width pentaquarks

A general study of pentaquarks built with four quarks in a L=1 state and an antiquark in S-wave shows that several of such states are forbidden by a selection rule, which holds in the limit of flavour symmetry, to decay into a baryon and a meson final state. We identify the most promising \bar{10} multiplet for the classification of the Theta^+ and Xi^{--} particles recently discovered with the prediction of a narrow width for both of them.

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arXiv2003

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 $Δm^2_{sol}$, 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.

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arXiv2003

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.

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arXiv2003

A statistical mechanics framework for multi-particle production in high energy reactions

We deduce the particle distributions in particle collisions with multihadron-production in the framework of mechanical statistics. They are derived as functions of x, P_T^2 and the rest mass of different species for a fixed total number of all produced particles, inelasticity and total transverse energy. For P_T larger than the mass of each particle we get the behaviour \frac{dn_i}{dP_T} \sim \sqrt{P_T} e^{-\frac{P_T}{T_H}} Values of _π, _K, and _{\bar{p}} in agreement with experiment are found by taking T_H=180MeV (the Hagedorn temperature).

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arXiv2002

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}.

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arXiv2001

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 $Δ\bar u(x)$ and $Δ\bar d(x)$.

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arXiv2001

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.

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