IFLP   13074
INSTITUTO DE FISICA LA PLATA
Unidad Ejecutora - UE
artículos
Título:
pi N --> pi N scattering and gamma N --> pi N photoproduction in within the improved born approximation
Autor/es:
A. MARIANO
Revista:
JOURNAL OF PHYSICS G-NUCLEAR AND PARTICLE PHYSICS
Editorial:
IOP PUBLISHING
Referencias:
Año: 2007 vol. 34 p. 1627 - 1651
ISSN:
0954-3899
Resumen:
Following the programme of describing consistently several processes where the isobar Delta(1232 MeV) nucleon resonance appears as an intermediate state, in this work we propose to unitarize our old improved Born approximation  already used to describe successfully pi + p  elastic and radiative scattering, totreat pion photoproduction. First we add the effect of final state interactions and make a new determination of the mass, width and the coupling constant to the pion–nucleon state of the Delta resonance. Then extending the model for pion photoproduction and using the resonance parameters determined previously,we are able to define effective form factors (at k_gamma ^ 2 = 0) for the gamma N --> Delta vertex with values GM = 2.97 +/- 0.08 and GE = 0.055 +/- 0.010, by fitting the data for the M_3/2 (1+) and E_3/2(1+)  multipoles. These values are fully consistent with recent chiral effective field theory calculations, and using them we canpredict satisfactorily the data for other multipoles and the photoproduction cross section. Finally, we intend amodel-independent determination of the bare form  factors making a dynamical dressing of the vertex, getting G_0M = 1.69 +/- 0.02, G_0E = 0.028 +/- 0.008 and R_0EM = −1.67 +/-  0.45%,  which are compared with  different quark models.