Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSpectral Content of Isoscalar Nucleon Form Factors
66
0
0.0
(
0
)
Authors
H.-W. Hammer
Ask ChatGPT about the research
No Arabic abstract
The nucleon strange vector and isoscalar electromagnetic form factors are studied using a spectral decomposition. The Kbar{K} contribution to the electric and magnetic radii as well as the magnetic moment is evaluated to all orders in the strong interaction using an analytic continuation of experimental KN scattering amplitudes and bounds from unitarity. The relationship between non-resonant and resonant Kbar{K} contributions to the form factors is demonstrated, and values for the vector and tensor phi Nbar{N} couplings are derived. The Kbar{K} spectral functions are used to evaluate the credibility of model calculations for the strange quark vector current form factors.
rate research
Read More
To obtain further information on the geometric shape of the nucleon, the proton charge form factor is decomposed into two terms, which are connected respectively with a spherically symmetric and an intrinsic quadrupole part of the protons charge density. Quark model relations are employed to derive expressions for both terms. In particular, the protons intrinsic quadrupole form factor is obtained from a relation between the N -> Delta and neutron charge form factors. The proposed decomposition shows that the neutron charge form factor is an observable manifestation of an intrinsic quadrupole form factor of the nucleon. Furthermore, it affords an interpretation of recent electron-nucleon scattering data in terms of a nonspherical distribution of quark-antiquark pairs in the nucleon.
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.
A group theoretical derivation of a relation between the N --> Delta charge quadrupole transition and neutron charge form factors is presented.
We study the electromagnetic structure of the nucleon within a hybrid constituent-quark model that comprises, in addition to the $3q$ valence component, also a $3q$+$pi$ non-valence component. To this aim we employ a Poincare-invariant multichannel formulation based on the point-form of relativistic quantum mechanics. With a simple 3-quark wave function for the bare nucleon, i.e. the $3q$-component, we obtain reasonable results for the nucleon form factors and predict the meson-cloud contribution to be significant only below $Q^2lesssim 0.5$,GeV$^2$ amounting to about 10% for $Q^2rightarrow 0$, in accordance with the findings of other authors.
The u- and d-quark contributions to the elastic nucleon electromagnetic form factors have been determined using experimental data on GEn, GMn, GpE, and GpM. Such a flavor separation of the form factors became possible up to 3.4 GeV2 with recent data on GEn from Hall A at JLab. At a negative four-momentum transfer squared Q2 above 1 GeV2, for both the u- and d-quark components, the ratio of the Pauli form factor to the Dirac form factor, F2/F1, was found to be almost constant, and for each of F2 and F1 individually, the d-quark portions of both form factors drop continuously with increasing Q2.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
