Relativistic quark spin coupling effects in the correlations between nucleon electroweak properties
Abstract We investigate the effect of different relativistic spin couplings of constituent quarks on nucleon electroweak properties. Within each quark spin coupling scheme the correlations between static electroweak observables are found to be independent of the particular shape of the momentum part of the nucleon light-front wave function. The neutron charge form factor is very sensitive to different choices of spin coupling schemes once the magnetic moment is fitted to the experimental value. However, it is found rather insensitive to the details of the momentum part of the three-quark wave function model.
Coulomb corrections to elastic electron–proton scattering and the proton charge radius
Abstract Recent values of the proton charge radius derived from the Lamb shift in electronic hydrogen tend to be larger than those from electron scattering. Therefore low-momentum-transfer scattering data from different experiments have been reanalyzed with Coulomb and recoil corrections included. This was done by calculating at each scattering angle and scattering energy the corresponding correction obtained from a partial wave program which includes recoil approximately. Corrections due to magnetic scattering were also made before the rms-radius was determined by a fit which allows free normalization for each experiment. It is shown that the inclusion of Coulomb corrections in the analysis of electron scattering data lowers the χ2 of the fit and increases the proton radius by about (0.008–0.013) fm depending on the fit strategy. A value of r p =0.880 (15) fm is obtained which is in good agreement with the one extracted from Lamb shift measurements.
Spin correlations, QCD color transparency, and heavy-quark thresholds in proton-proton scattering.
The strikingly large spin-spin correlation A/sub N//sub N/ observed in pp elastic scattering at p/sub lab/ = 2.5 and 11.75 GeVc and the unexpected energy dependence of absorptive corrections to quasielastic proton-proton scattering in a nuclear target can be interpreted in terms of two J = L = S = 1, B = 2 resonance structures associated with the strange- and charmed-particle production thresholds, interfering with a perturbative QCD background. The results provide support for the ''color-transparency'' phenomenon predicted in perturbative QCD away from resonances or heavy-quark thresholds.