| Full text | |
| Author(s): |
Ramalho, G.
Total Authors: 1
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| Document type: | Journal article |
| Source: | EUROPEAN PHYSICAL JOURNAL A; v. 55, n. 3, p. 14-pg., 2019-03-05. |
| Abstract | |
.Models based on SU(6) symmetry breaking and large N-c limit provide relations between the pion cloud contributions to the *N(1232) quadrupole form factors, electric (G(E)) and Coulomb (G(C)), and the neutron electric form factor G(En), suggesting that those form factors are dominated by the same physical processes. Those relations are improved in order to satisfy a fundamental constraint between the electric and Coulomb quadrupole form factors in the long wavelength limit, when the photon three-momentum vanishes (Siegert's theorem). Inspired by those relations, we study alternative parametrizations for the neutron electric form factor. The parameters of the new form are then determined by a combined fit to the G(En) and the *N(1232) quadrupole form factor data. We obtain a very good description of the G(E) and G(C) data when we combine the pion cloud contributions with small valence quark contributions to the *N(1232) quadrupole form factors. The best description of the data is obtained when the second momentum of G(En) is rn4 similar or equal to-0.4 fm(4). We conclude that the square radii associated with G(E) and G(C), rE2 and rC2, respectively, are large, revealing the long extension of the pion cloud. We conclude also that those square radii are related by rE2-rC2=0.6 +/- 0.2 fm(2). The last result is mainly the consequence of the pion cloud effects and Siegert's theorem. (AU) | |
| FAPESP's process: | 17/02684-5 - Study of the electromagnetic and axial structure of the baryons in the vacuum and in nuclear medium |
| Grantee: | Gilberto Tomás Ferreira Ramalho |
| Support Opportunities: | Research Grants - Young Investigators Grants |