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Register a new userElectromagnetic form factors of the nucleon: new fit and analysis of uncertainties
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Electromagnetic form factors of proton and neutron, obtained from a new fit of data, are presented. The proton form factors are obtained from a simultaneous fit to the ratio $mu_p G_{Ep}/G_{Mp}$ determined from polarization transfer measurements and to $ep$ elastic cross section data. Phenomenological two-photon exchange corrections are taken into account. The present fit for proton was performed in the kinematical region $Q^2in (0,6)$ GeV$^2$. Both for protons and neutrons we use the latest available data. For all form factors the uncertainties and correlations of form factor parameters are investigated with the $chi^2$ method.
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By the analysis of the world data base of elastic electron scattering on the proton and the neutron (for the latter, in fact, on $^2H$ and $^3He$) important experimental insights have recently been gained into the flavor compositions of nucleon electromagnetic form factors. We report on testing the Graz Goldstone-boson-exchange relativistic constituent-quark model in comparison to the flavor contents in low-energy nucleons, as revealed from electron-scattering phenomenology. It is found that a satisfactory agreement is achieved between theory and experiment for momentum transfers up to $Q^2sim$ 4 GeV$^2$, relying on three-quark configurations only. Analogous studies have been extended to the $Delta$ and the hyperon electromagnetic form factors. For them we here show only some sample results in comparison to data from lattice quantum chromodynamics.
The data on the proton form factors in the time-like region from the BaBar, BESIII and CMD-3 Collaborations are examined to have coherent pieces of information on the proton structure. Oscillations in the annihilation cross section, previously observed, are determined with better precision. The moduli of the individual form factors, determined for the first time, their ratio and the angular asymmetry of the annihilation reaction $e^+e^-tobar p p$ are discussed. Fiits of the available data on the cross section, the effective form factor, and the form factor ratio, allow to propose a description of the electric and magnetic time-like form factors from the threshold up to the highest momenta.
The fomalism is developed to express nucleon matrix elements of the electromagnetic current in terms of form factors consistent with the translational, rotational, and parity symmetries of a cubic lattice. We calculate the number of these form factors and show how appropriate linear combinations approach the continuum limit.
The nucleon electromagnetic form factors are calculated in light cone QCD sum rules framework using the most general form of the nucleon interpolating current. Using two forms of the distribution amplitudes (DAs), predictions for the form factors are presented and compared with existing experimental data. It is shown that our results describe remarkably well the existing experimental data.
The role of the strange quarks on the low-energy interactions of the proton can be probed through the strange electromagnetic form factors. Knowledge of these form factors provides essential input for parity-violating processes and contributes to the understanding of the sea quark dynamics. We determine the strange electromagnetic form factors of the nucleon within the lattice formulation of Quantum Chromodynamics using simulations that include light, strange and charm quarks in the sea all tuned to their physical mass values. We employ state-of-the-art techniques to accurately extract the form factors for values of the momentum transfer square up to 0.8~GeV$^2$. We find that both the electric and magnetic form factors are statistically non-zero. We obtain for the strange magnetic moment $mu^s=-0.017(4)$, the strange magnetic radius $langle r^2_M rangle^s=-0.015(9)$~fm$^2$, and the strange charge radius $langle r^2_E rangle^s=-0.0048(6)$~fm$^2$.
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