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.
Study of the in-medium nucleon electromagnetic form factors using a light-front nucleon wave function combined with the quark-meson coupling model
Abstract We study the nucleon electromagnetic (EM) form factors in symmetric nuclear matter as well as in vacuum within a light-front approach using the in-medium inputs calculated by the quark-meson coupling model. The same in-medium quark properties are used as those used for the study of in-medium pion properties. The zero of the proton EM form factor ratio in vacuum, the electric to magnetic form factor ratio μ p G E p ( Q 2 ) / G M p ( Q 2 ) ( Q 2 = − q 2 > 0 with q being the four-momentum transfer), is determined including the latest experimental data by implementing a hard constituent quark component in the nucleon wave function. A reasonable fit is achieved for the ratio μ p G E p ( Q 2 ) / G M p ( Q 2 ) in vacuum, and we predict that the Q 0 2 value to cross the zero of the ratio to be about 15 GeV2. In addition the double ratio data of the proton EM form factors in 4He and H nuclei, [ G E p 4 He ( Q 2 ) / G 4 He M p ( Q 2 ) ] / [ G E p 1 H ( Q 2 ) / G M p 1 H ( Q 2 ) ] , extracted by the polarized ( e → , e ′ p → ) scattering experiment on 4He at JLab, are well described. We also predict that the Q 0 2 value satisfying μ p G E p ( Q 0 2 ) / G M p ( Q 0 2 ) = 0 in symmetric nuclear matter, shifts to a smaller value as increasing nuclear matter density, which reflects the facts that the faster falloff of G E p ( Q 2 ) as increasing Q 2 and the increase of the proton mean-square charge radius. Furthermore, we calculate the neutron EM form factor double ratio in symmetric nuclear matter for 0.1 Q 2 1.0 GeV2. The result shows that the neutron double ratio is enhanced relative to that in vacuum, while for the proton it is quenched, and agrees with an existing theoretical prediction.
Constitutional Identity in the EU— A Shield or a Sword?
This Article consists of five sections. In the first section, it describes why identity questions matter, particularly in Europe. In the second section, the Article tackles the issue of multiple structural ambiguities affecting the concept of constitutional identity in the European constitutional vocabulary. In the third section, the Article explores trends concerning the use of constitutional identity in the European legal discourse and practice, including the development of alternative interpretations and applications of the notion of constitutional identities in the Member States. The fourth section of the Article combines the analytical accounts outlined in the second section with the trends identified in the third section, contending that different conceptions and applications of constitutional identity have varying effects on the European composite constitutional adjudication system and that the institutional and procedural framework should be calibrated accordingly. The final section of this Article draws some conclusions.