Elastic electromagnetic form factors of nucleons are investigated both for the time-like and the space-like momentums under the condition that the QCD constraints are satisfied asymptotically. The unsubtracted dispersion relation with the superconvergence conditions are used as a realization of the QCD conditions. The experimental data are analyzed by using the dispersion formula and it is shown that the calculated form factors reproduce the experimental data reasonably well.
Yukawa couplings in the Lorentz- and $CPT$-violating Standard Model Extension (SME) induce quantum contributions to the electromagnetic moments of quarks, which are calculated in the present paper and then used to define contributions to electromagnetic moments of nucleons. High-sensitivity measurements of the proton and neutron electromagnetic moments then yield constrains on SME coefficients, reaching bounds as restrictive as $10^{-12}$. This approach notably grants access to SME effects from the second and third quark families.
We present an improved study of the electromagnetic form factors of the nucleon and of the Roper-nucleon transition using an extended version of the effective action of soft-wall AdS/QCD. We include novel contribution from additional non-minimal terms, which do not renormalize the charge and do not change the normalization of the corresponding form factors, but the inclusion of these terms results in an important contribution to the momentum dependence of the form factors and helicity amplitudes.
Testing axial and electromagnetic nucleon form factors in time-like regions in the processes $\bar p + n\to π^- +\ell^-+\ell^+$ and $\bar p+ p\to π^0 +\ell^- + \ell^+$, $\ell=e$, $μ$
The quantum phase-space approach allows one to define relativistic spatial distributions inside a target with arbitrary spin and arbitrary average momentum. We apply this quasiprobabilistic formalism to the whole electromagnetic four-current operator in the case of spin-$0$ and spin-$\frac{1}{2}$ targets, study in detail the frame dependence of the corresponding spatial distributions, and compare our results with those from the light-front formalism. While former works focused on the charge distributions, we extend here the investigations to the current distributions. We clarify the role playe…
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 transv…
We compute the cross section for the electromagnetic annihilation into charged leptons, and the electromagnetic scattering off nucleons, of spin-3/2 self-conjugate (Majorana) particles using the general form of the electromagnetic vertex function that was obtained previously for such particles. In addition to the restrictions imposed by common principles such as electromagnetic gauge invariance and hermiticity, the vertex function incorporates the restriction due to the Majorana condition as well as the particular properties related to the spinors in the Rarita-Schwinger representation, and is…
The sea quark contributions to the nucleon electromagnetic form factors from up, down and strange quarks are studied with the nonlocal chiral effective Lagrangian. Both octet and decuplet intermediate states are included in the one loop calculation. Compared with the strange form factors, though their signs are the same, the absolute value of the light quark form factors are much larger. For both electric and magnetic form factors, the contribution from $d$ quark is larger than that from $u$ quark. The current lattice data for the light-sea quark form factors are between our sea quark results …
From QCD-Based Descriptions to Direct Fits: A Unified Study of Nucleon Electromagnetic Form Factors
Shahrood University of Technology（沙赫鲁德理工大学）；Departament de Física, Universitat Autònoma de Barcelona, The Barcelona Institute of Science and Technology (BIST),and Institut de Física d’Altes Energies (IFAE)（巴塞罗那自治大学物理系、巴塞罗那科学与技术研究院及高能物理研究所）
Using baryon chiral perturbation theory including vector mesons, we analyse various continuum contributions to the isoscalar electromagnetic spectral functions of the nucleon induced by the leading order couplings.
The study of electromagnetic and weak form factors of nucleon (charged quasielastic scatterings of neutrino (antineutrino) and nucleon) done in $70^\prime s$ and published in Chinese journals is reviewed. In the approach of the study antiquark components are introduced to the wave functions of nucleon and the study shows that the antiquark components of nucleon play an essential role in the EM and weak form factors of nucleon. The SU(6) symmetric wave functions of baryons in the rest frame ( s-wave in the rest frame) have been constructed. In these wave functions there are both quark and antiq…
External electromagnetic fields can provoke stress, and thus modifications of the internal structure of nucleons. Working with this hypothesis, one can derive a simple description of the charge dependence of the EMC effect. This first result is confirmed by two explicit models of the structure functions of deformed nucleons in the atomic nucleus. For large nuclei a continuous model is used. For small nuclei a discrete distribution of nuclear matter gives better results.
Taking into account the PDFs, obtained by different Collaborations, the momentum transfer dependence of GPDs of the nucleons is obtained. The calculated electromagnetic and gravitomagnetic form factors of nucleons are used for the description of different form factors and the nucleons elastic scattering in a wide energy and momentum transfer region with a minimum number of fitting parameters. The electromagnetic and gravitomagnetic radii of the nucleon are calculated using the obtained momentum transfer dependence of GPDs with different forms of PDFs obtained by different Collaborations. The c…
