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Titolo: SU(6) breaking effects in the nucleon elastic electromagnetic form factors art. no. 065201
Autore: Cardarelli, F; Simula, S;
 Indirizzi:
 Ist Nazl Fis Nucl, Sez Roma 3, I00146 Rome, Italy Ist Nazl Fis Nucl Rome Italy I00146 cl, Sez Roma 3, I00146 Rome, Italy
 Titolo Testata:
 PHYSICAL REVIEW C
fascicolo: 6,
volume: 6206,
anno: 2000,
pagine: 5201 
 SICI:
 05562813(200012)6206:6<5201:SBEITN>2.0.ZU;2U
 Fonte:
 ISI
 Lingua:
 ENG
 Soggetto:
 CONSTITUENT QUARKMODEL; LIGHTBARYON; DYNAMICS; NEUTRON; CHROMODYNAMICS; DEUTERON; PION;
 Tipo documento:
 Article
 Natura:
 Periodico
 Settore Disciplinare:
 Physical, Chemical & Earth Sciences
 discip_EC
 Citazioni:
 27
 Recensione:
 Indirizzi per estratti:
 Indirizzo: Cardarelli, F Ist Nazl Fis Nucl, Sez Roma 3, Via Vasca Navale 84, I00146 Rome, Italy Ist Nazl Fis Nucl Via Vasca Navale 84 Rome Italy I00146 ly



 Citazione:
 F. Cardarelli e S. Simula, "SU(6) breaking effects in the nucleon elastic electromagnetic form factors art. no. 065201", PHYS REV C, 6206(6), 2000, pp. 5201
Abstract
The effects of both kinematical and dynamical SU(6) breaking on the nucleon elastic form factors, G(E)(N)(Q(2)) and G(M)(N)(Q(2)), are investigated within the constituent quark model formulated on the light front. The investigation is focused on G(E)(n)(Q(2)) and the ratio G(M)(p)(Q(2))/G(M)(n)(Q(2)), which within the SU(6) symmetry are given by; G(E)(n)(Q(2))=0 and G(M)(p)(Q(2))/G(M)(n)(Q(2))=3/2, respectively. It is shown that the kinematicalSU(6) breaking caused by the Melosh rotations of the quark spins as well as the dynamical SU(6) breaking due to the mixedsymmetry component generated in the nucleon wave function by the spindependent terms of the quarkquark interaction, can affect both G(E)(n)(Q(2)) and G(M)(p)(Q(2))/G(M)(n)(Q(2)). The calculated G(E)(n)(Q(2)) is found to be qualitatively consistent with existing data, though only similar or equal to 65% of the experimental neutron charge radius can be explained without invoking effects from possible nonvanishing sizes of the constituent quarks and/or manybody currents. At the same time the predictions for the magnetic ratio G(M)(p)(Q(2))/G(M)(n)(Q(2)) turn out to be inconsistent with the data. It is, however, shown that the calculations of G(M)(N)(Q(2)) based on different components of the onebody electromagnetic current lead to quite different results. In particular, the calculations based on the plus component are found to be plagued by spurious effects related to the loss of the rotational covariance in the lightfront formalism. These unwanted effects can be avoided by consideringthe transverse y component of the current. In this way our lightfront predictions are found to be consistent with the data on both G(E)(n)(Q(2)) andG(M)(p)(Q(2))/G(M)(n)(Q(2)). Finally, it is shown that a suppression of the ratio G(E)(p)(Q(2))/G(M)(p)(Q(2)) With respect to the dipolefit prediction can be expected in the constituent quark model provided the relativisticeffects generated by the Melosh rotations of the constituent spins are taken into account.
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Documento generato il 31/03/20 alle ore 04:49:30