arXiv subjects

Franco Buccella

Publications and source records attributed to Franco Buccella.

At least 19 recordsLinked to original sources

arXiv2023

Analysis of HERA data with a PDF parametrization inspired by quantum statistical mechanics

We present a determination of the parton distribution functions (PDFs) of the proton from HERA data using a PDF parametrization inspired by a quantum statistical model of the proton dynamics. This parametrization is characterised by a very small number of parameters, yet it leads to a reasonably good description of the data, comparable with other parametrizations on the market. It may thus provide an alternative to standard parametrizations, useful for studying parametrization bias and to possibly simplify the fit procedure thanks to the small number of parameters. Interestingly, the model reproduces key physical features, such as a $\bar d$ distribution larger than $\bar u$, that HERA data alone are not able to constrain when using more flexible parametrizations. Moreover, polarized distributions are described in the model by the same parameters of the unpolarized ones, giving us the possibility of extracting both types of distributions within the same fit.

hep-ph↗

arXiv2023

Raoul Gatto and Bruno Touschek's joint legacy in the rise of electron-positron physics

Raoul Gatto and Bruno Touschek's collaboration in the establishment of electron positron colliders as a fundamental discovery tool in particle physics will be illustrated. In particular, we will tell the little-known story of how Gatto and Touschek's pioneering vision combined to provide the theoretical foundations for AdA, the first matter-antimatter collider, and how their friendship with Wolfgang Pauli and Gerhard L\"uders was crucial to their understanding of the CPT theorem, the basis for AdA's success. We will see how these two exceptional scientists shaped physics between Rome and Frascati, from the proposal to build AdA and, soon after in 1961, the larger machine ADONE, to the discovery of the $J/\Psi$ particle in 1974. We will also highlight Gatto and Touschek's contribution in mentoring an extraordinary cohort of students and collaborators whose work contributed to the renaissance of Italian theoretical physics after the Second World War and to the establishment of the Standard Model of particle physics.

physics.hist-ph↗

arXiv2023

Extraction of Kaon Partonic Distribution Functions from Drell-Yan and $J/ψ$ Production Data

We present an analysis to extract kaon parton distribution functions (PDFs) for the first time using meson-induced Drell-Yan and quarkonium production data. Starting from the statistical model first developed for determining the partonic structure of spin-1/2 nucleon and later applied to the spin-0 pion, we have extended this approach to perform a global fit to existing kaon-induced Drell-Yan and $J/ψ$ production data. These data are well described by the statistical model, allowing a first extraction of the kaon PDFs. We find that both the Drell-Yan and the $J/ψ$ data favor a harder valence distribution for strange quark than for up quark in kaon. The kaon gluon distribution is further constrained by the $J/ψ$ production data. In particular, the momentum fraction carried by gluons is found to be similar for pion and kaon.

hep-ph↗

arXiv2022

Planck Formula for the Gluon Parton Distribution in the Proton

We describe the gluon parton distribution function (PDF) in the proton, deduced by data from the ATLAS and HERA experiments, in the framework of the parton statistical model. The best fit parameters involved in the Planck formula that describes the gluon distribution are consistent with the results obtained from analysis of deep inelastic scattering processes. Remarkably, the agreement between the statistical model and the experimental gluon distributions is found with the same value of the "temperature" parameter $\bar{x}$ found by fitting the valence parton distributions from deep inelastic scattering. This result corroborates the validity of the statistical approach in the gluon sector.

hep-ph↗

arXiv2020

A New Extraction of Pion Parton Distributions in the Statistical Model

We present a new analysis to extract pion's parton distribution functions (PDFs) in the framework of the statistical model. Starting from the statistical model framework first developed for the spin-1/2 nucleon, we apply appropriate modifications taking into account the spin-0 nature of pion and the isospin and charge-conjugation symmetry properties. This results in a significant reduction of the number of parameters compared to a recent work to extract pion's PDFs. Using $π^-$-induced Drell-Yan data to determine the parameters of this statistical model approach, we show that a good description of these experimental data with Next-to-Leading order QCD calculations can be obtained. Good agreement between the calculations and the $π^+/π^-$ Drell-Yan cross section ratio data, not included in the global fit, has confirmed the predictive power of these new pion PDFs.

hep-ph↗

arXiv2019

On $SU(3)_{F}$ Breaking through Final State Interactions and CP Asymmetries in $D\to P P$ Decays

We analyse $D$ decays to two pseudoscalars $(π,K)$ assuming the dominant source of $\mathrm{SU}(3)_F$ breaking lies in final state interactions. We obtain an excellent agreement with experimental data and are able to predict CP violation in several channels based on current data on branching ratios and $Δ\mathrm{A_{CP}}$. We also make predictions for $δ_{Kπ}$ and the branching fraction for the decay $D_s^+\to K^+K_L$.

hep-ph↗

arXiv2018

Neutrino phenomenology from leptogenesis

Assuming a type-I seesaw mechanism for neutrino mass generation and invoking a baryogengesis via leptogenesis scenario, we consider a reasonable hierarchical structure for Dirac neutrino mass matrix, similar to up-type quark mass matrix. These hypotheses imply a relevant connection between high scale CP violation and low energy one. By requiring a compact heavy neutrino mass spectrum, which allows to circumvent Davidson-Ibarra limit, one can obtain an efficient leptogenesis restricting the allowed region for low energy neutrino parameters. Once the oscillating parameters are taken inside a $3σ$ range, through the numerical resolution of the leptogenesis Boltzmann equations one gets the following allowed intervals for the lightest neutrino mass and the Dirac CP phase: $-0.90π<δ<-0.75π$ and $m_1\sim( 0.002 - 0.004)$ eV.

hep-ph↗

arXiv2018

b decays: a factory for hidden charm multiquark states

We assume that the two hidden charm pentaquark discovered at $LHCb$ are built by the three light quarks and the $c \bar{c}$ pair, both colour octets. in relative P-wave for the $\frac{5}{2}^+$ state and by the eigenvectors of the chromomagnetic interaction for the five constituents in S-wave for the four $\frac{3}{2}^-$ state with masses $4360$, $4410$, $4490$ and $4560$ MeV . The "open channel" $p $ $J/ψ$ has large components along the two first states and so appear as the $4380$ resonance and the $Λ_c$ $ \bar{D}^{0*}$ and $Σ_c$ $\bar{D}^*$ are "open channels" for the lower and higher resonances, respectively. The expectation for their strange isoscalar partners is to have a mass larger by an amount of the order or smaller than the $M_Λ - M_N$ mass difference. We account for the small width of the $\frac{5}{2}^+$, since its decay needs the exchangeof a gluon and stress that the decays of particles with "beauty" provide the best experimental framework for the discovery of hidden charm multiquarks. The relevance of the production mechanics shows the reason why only some of the states with non minimal number of constituents have been found.

hep-ph↗

arXiv2014

A Check-up for the Statistical Parton Model

We compare the parton distributions deduced in the framework of a quantum statistical approach for both the longitudinal and transverse degrees of freedom with the unpolarized distributions measured at Hera and with the polarized ones proposed in a previous paper, which have been shown to be in very good agreement also with the results of experiments performed after that proposal. The agreement with Hera data in correspondence of very similar values for the 'temperature' and the 'potentials' found in the previous work gives a robust confirm of the statistical model. The feature of describing both unpolarized and polarized parton distributions in terms of few parameters fixed by data with large statistics and small systematic errors makes very attractive the parametrization proposed here.

hep-ph↗

arXiv2014

How large is the gluon polarization in the statistical parton distributions approach?

We review the theoretical foundations of the quantum statistical approach to parton distributions and we show that by using some recent experimental results from Deep Inelastic Scattering, we are able to improve the description of the data by means of a new determination of the parton distributions. We will see that a large gluon polarization emerges, giving a significant contribution to the proton spin.

hep-ph↗

arXiv2014

New results in the quantum statistical approach to parton distributions

We will describe the quantum statistical approach to parton distributions allowing to obtain simultaneously the unpolarized distributions and the helicity distributions. We will present some recent results, in particular related to the nucleon spin structure in QCD. Future measurements are challenging to check the validity of this novel physical framework.

hep-ph↗

arXiv2014

Statistical description of the flavor structure of the nucleon sea

The theoretical foundations of the quantum statistical approach to parton distributions are reviewed together with the phenomenological motivations from a few specific features of Deep Inelastic Scattering data. The chiral properties of QCD lead to strong relations between quarks and antiquarks distributions and automatically account for the flavor and helicity symmetry breaking of the sea. We are able to describe both unpolarized and polarized structure functions in terms of a small number of parameters. The extension to include their transverse momentum dependence will be also briefly considered.

hep-ph↗

arXiv2013

CP violation in D meson decays: would it be a sign of new physics ?

Ascribing the large SU(3) violations in the Cabibbo forbidden decays of neutral D mesons to the final state interactions, one gets large strong phase differences, necessary for substantial direct CP violation. While the absolute value of the CP violating asymmetries depend on the uncertain strength of the penguin contribution, we predict an asymmetry for the decays into charged pions more than twice as large and having opposite sign with respect to that for charged kaons.

hep-ph↗

arXiv2013

$W^{\pm}$ bosons production in the quantum statistical parton distributions approach

We consider $W^{\pm}$ gauge bosons production in connection with recent results from BNL-RHIC and FNAL-Tevatron and interesting predictions from the statistical parton distributions. They concern relevant aspects of the structure of the nucleon sea and the high-$x$ region of the valence quark distributions. We also give predictions in view of future proton-neutron collisions experiments at BNL-RHIC.

hep-ph↗

arXiv2013

The transverse momentum dependent statistical parton distributions revisited

The extension of the statistical parton distributions to include their transverse momentum dependence (TMD) is revisited by considering that the proton target has a finite longitudinal momentum. The TMD will be generated by means of a transverse energy sum rule. The new results are mainly relevant for electron-proton inelastic collisions in the low $Q^2$ region. We take into account the effects of the Melosh-Wigner rotation for the helicity distributions.

hep-ph↗

arXiv2012

Squeezing out predictions with leptogenesis from SO(10)

We consider the see-saw mechanism within a non-supersymmetric SO(10) model. By assuming the SO(10) quark-lepton symmetry, and after imposing suitable conditions that ensure that the right-handed (RH) neutrino masses are at most mildly hierarchical (compact RH spectrum) we obtain a surprisingly predictive scenario. The absolute neutrino mass scale, the Dirac and the two Majorana phases of the neutrino mixing matrix remain determined in terms of the set of already measured low energy observables, modulo a discrete ambiguity in the signs of two neutrino mixing angles and of the Dirac phase. The RH neutrinos mass spectrum is also predicted, as well as the size and sign of the leptogenesis CP asymmetries. We compute the cosmological baryon asymmetry generated through leptogenesis and obtain the correct sign and a size compatible with observations.

hep-ph↗

arXiv2012

The statistical model for parton distributions

The phenomenological motivations, the expressions and the comparison with experiment of the parton distributions inspired by the quantum statistics are described. The Fermi-Dirac expressions for the quarks and their antiparticles automatically account for the correlation between the shape and the first moments of the valence partons, as well as the flavor and spin asymmetries of the sea. One is able to describe with a small number of parameters both unpolarized and polarized structure functions.

hep-ph↗

arXiv2011

Semiinclusive DIS cross sections and spin asymmetries in the quantum statistical parton distributions approach

We consider the extension of the statistical parton distributions to include their transverse momentum dependence, by using two different methods, one is based on our quantum statistical approach, the other on a relativistic covariant method. We take into account the effects of the Melosh-Wigner rotation for the polarized distributions. The results obtained can be compared with recent semiinclusive Deep Inelastic Scattering data on the cross section and double longitudinal-spin asymmetries from JLab. We also give some predictions for future experiments on electron-neutron scattering.

hep-ph↗