arXiv subjects

Antonio Silva

Publications and source records attributed to Antonio Silva.

13 recordsLinked to original sources

arXiv2025

Model Comparisons of Transverse Energy and Charged-Particle Multiplicity in A+A Collisions at Midrapidity from $\sqrt{s_{NN}}$ $=$ 7.7 to 200~GeV

We present a comprehensive comparison of PHENIX measurements of transverse energy production ($dE_T/dη$) and charged-particle multiplicity ($dN/dη$) at midrapidity to simulations from PYTHIA-8, AMPT, HIJING, and SMASH. These comparisons span both small systems (d+Au, $^3$He+Au) and large systems (Cu+Cu, Cu+Au, Au+Au, and U+U) at $\sqrt{s_{NN}}$ $\sim$ 200~GeV and Au+Au over a range of beam energies $\sqrt{s_{NN}} = 7.7$--200~GeV. Using the Rivet framework, we assess the performance of these models. While general trends are captured, significant deviations persist, particularly in low-energy and peripheral collisions, underscoring the need for improved modeling of baryon stopping and energy deposition mechanisms.

nucl-ex↗

arXiv2017

Flavour structure of the nucleon electromagnetic form factors and transverse charge densities in the chiral quark-soliton model

We investigate the flavour decomposition of the electromagnetic form factors of the nucleon, based on the chiral quark-soliton model ($χ$QSM) with symmetry-conserving quantisation. We consider the rotational $1/N_c$ and linear strange-quark mass ($m_s$) corrections. We discuss the results of the flavour-decomposed electromagnetic form factors in comparison with the recent experimental data. In order to see the effects of the strange quark, we compare the SU(3) results with those of SU(2). We finally discuss the transverse charge densities for both unpolarised and polarised nucleons. The transverse charge density inside a neutron turns out to be negative in the vicinity of the centre within the SU(3) $χ$QSM, which can be explained by the contribution of the strange quark.

hep-ph↗

arXiv2011

Tensor properties of the nucleon

We report in the present talk recent results of the tensor properties of the nucleon within the framework of the chiral quark-soliton model. The tensor and anomalous tensor magnetic form factors are calculated for the momentum transfer up to $Q^{2}\leq1\,\mathrm{GeV}^{2}$ and at a renormalization scale of $0.36\,\mathrm{GeV}^{2}$. The main results are summarized as follows: the flavor tensor charges of the nucleon are yielded as $δu=1.08$, $δd=-0.31$, $δs=-0.01$, while the up and down anomalous tensor magnetic moments are evaluated as $κ_{T}^{u}=3.56$ and $κ_{T}^{d}=1.83$, respectively. The strange anomalous tensor magnetic moment turns out to be $κ_{T}^{s}=0.2\sim -0.2$, compatible with zero. We discuss their physical implications, comparing them in particular with those from the lattice QCD.

hep-ph↗

arXiv2010

Anomalous tensor magnetic moments and form factors of the proton in the self-consistent chiral quark-soliton model

We investigate the form factors of the chiral-odd nucleon matrix element of the tensor current. In particular, we aim at the anomalous tensor magnetic form factors of the nucleon within the framework of the SU(3) and SU(2) chiral quark-soliton model. We consider $1/N_c$ rotational corrections and linear effects of SU(3) symmetry breaking with the symmetry-conserving quantization employed. We first obtain the results of the anomalous tensor magnetic moments for the up and down quarks: $κ_{T}^{u}=3.56$ and $κ_{T}^{d}=1.83$, respectively. The strange anomalous tensor magnetic moment is yielded to be $κ_{T}^{s}=0.2\sim -0.2$, that is compatible with zero. We also calculate the corresponding form factors $κ_{T}^{q}(Q^{2})$ up to a momentum transfer $Q^{2}\leq 1\,\mathrm{GeV}^{2}$ at a renormalization scale of $0.36\,\mathrm{GeV}^{2}$.

hep-ph↗

arXiv2010

Tensor charges and form factors of SU(3) baryons in the self-consistent SU(3) chiral quark-soliton model

We investigate the tensor form factors of the baryon octet within the framework of the chiral quark-soliton model, emphasizing those of the nucleon, taking linear 1/N_c rotational as well as linear m_s corrections into account, and applying the symmetry-conserving quantization. We explicitly calculate the tensor form factors H_{T}^{q}(Q^{2}) corresponding to the generalized parton distributions H_{T}(x,ξ,t). The tensor form factors are obtained for the momentum transfer up to Q^{2}\leq1\,\mathrm{GeV}^{2} and at a renormalization scale of 0.36\,\mathrm{GeV}^{2}. We find for the tensor charges δu=1.08, δd=-0.32, δs=-0.01 and discuss their physical consequences, comparing them with those from other models. Results for tensor charges for the baryon octet are also given.

hep-ph↗

arXiv2008

Electromagnetic properties of the Delta(1232) and decuplet baryons in the self-consistent SU(3) chiral quark-soliton model

We examine the electromagnetic properties of the Delta(1232) resonance within the self-consistent chiral quark-soliton model. In particular we present the Delta form factors of the vector-current GE0, GE2 and GM1 for a momentum-transfer range of $Q^{2} \leq 1GeV^{2}$. We apply the symmetry-conserving quantization of the soliton and take 1/N_c rotational corrections into account. Values for the magnetic moments of all decuplet baryons as well as for the N-Delta transition are given. Special interest is also given to the electric quadrupole moment of the Delta.

hep-ph↗

arXiv2008

Semileptonic hyperon decays in the self-consistent SU(3) chiral quark-soliton model

We investigate the semileptonic hyperon decays within the framework of the self-consistent SU(3) chiral quark-soliton model ($χ$QSM). We take linear $1/N_c$ rotational as well as linear $m_s$ corrections into account and apply the symmetry conserving quantization. We present the results for the form factors $f_1(Q^2)$, $f_2(Q^2)$ and $g_1(Q^2)$ in addition to the semileptonic decay constants of hyperons. We also have calculated the radii and dipole masses of these form factors for all relevant strangeness-conserving and strangeness-changing transitions.

hep-ph↗

arXiv2006

Strange nucleon form factors: Solitonic approach to $G_{M}^{s}$, $G_{E}^{s}$, $\tilde{G}_{A}^{p}$ and $\tilde{G}_{A}^{n}$ and comparison with world data

We summarize the results of the chiral quark-soliton model ($χ$QSM) concerning basically all form factors necessary to interpret the present data of the parity violating electron scattering experiments SAMPLE, HAPPEX, A4 and G0. The results particularly focus on the recently measured asymmetries and the detailed data for various combinations of $G_{M}^{s}$, $G_{E}^{s}$, $\tilde{G}_{A}^{p}$ and $\tilde{G}_{A}^{n}$ at $Q^2=0.1$ GeV$^2$. The calculations yield positive strange magnetic and electric form factors and a negative axial vector one, all being rather small. The results are very close to the combined experimental world data from parity violating electron scattering and elastic $νp$- and $\bar{νp}$- scattering.

hep-ph↗

arXiv2006

Electric properties of the baryon anti-decuplet in the SU(3) chiral quark-soliton model

We investigate the electric form factors and charge radii of the pentaquark baryons within the framework of the chiral quark-soliton model. We consider the rotational $1/N_c$ and linear $m_s$ corrections, assuming isospin symmetry and employing the symmetry-conserving quantization. The flavor-decomposed charge densities of the $Θ^+$ are presented. The electric form factors and charge radii of the charged pentaquark baryons turn out to be very similar to those of the corresponding octet baryons. The charge radii of the neutral pentaquark baryons are obtained to be very tiny and positive. The strange electric form factor of the pentaquark proton is shown to be larger than the corresponding one of the proton by around 20%. We also present the charge radii of the baryon decuplet for comparison.

hep-ph↗

arXiv2006

Parity-violating aysmmetries in elastic $\vec{e}p$ scattering in the chiral quark-soliton model: Comparison with A4, G0, HAPPEX and SAMPLE

We investigate parity-violating electroweak asymmetries in the elastic scattering of polarized electrons off protons within the framework of the chiral quark-soliton model ($χ$QSM). We use as input the former results of the electromagnetic and strange form factors and newly calculated SU(3) axial-vector form factors, all evaluated with the same set of four parameters adjusted several years ago to general mesonic and baryonic properties. Based on this scheme, which yields positive electric and magnetic strange form factors with a $μ_s=(0.08-0.13)μ_N$, we determine the parity-violating asymmetries of elastic polarized electron-proton scattering. The results are in a good agreement with the data of the A4, HAPPEX, and SAMPLE experiments and reproduce the full $Q^2$-range of the G0-data. We also predict the parity-violating asymmetries for the backward G0 experiment.

hep-ph↗

arXiv2005

Axial-vector form factors of the nucleon within the chiral quark-soliton model and their strange components

We investigate three different axial-vector form factors of the nucleon, $G_A^{0}$, $G_A^3$, $G_A^8$, within the framework of the SU(3) chiral quark-soliton model, emphasizing their strangeness content. We take into account the rotational $1/N_c$ and linear strange quark ($m_s$) contributions using the symmetry-conserving SU(3) quantization and assuming isospin symmetry. The strange axial-vector form factor is also obtained and they all are discussed in the context of the parity-violating scattering of polarized electrons off the nucleon and its relevance to the strange vector form factors.

hep-ph↗

arXiv2004

Strange and singlet form factors of the nucleon: Predictions for G0, A4, and HAPPEX-II experiments

We investigate the strange and flavor-singlet electric and magnetic form factors of the nucleon within the framework of the SU(3) chiral quark-soliton model. Isospin symmetry is assumed and the symmetry-conserving SU(3) quantization is employed, rotational and strange quark mass corrections being included. For the experiments G0, A4, and HAPPEX-II we predict the quantities $G^{0}_E + βG^{0}_M$ and $G^{\rm s}_E + βG^{\rm s}_M$. The dependence of the results on the parameters of the model and the treatment of the Yukawa asymptotic behavior of the soliton are investigated.

hep-ph↗

arXiv2002

Strange vector form factors in the context of the SAMPLE, A4, HAPPEX and G0 experiments

We present the recent results of the strange vector form factors of the nucleon within the framework of the SU(3) chiral quark-soliton model. We compare our results with the recent experimental data of the SAMPLE and HAPPEX collaborations and find that they are in a good agreement with the data. We also predict the future experiments of the A4, HAPPEX-II and G0 collaborations.

hep-ph↗