arXiv:nucl-th/0601037·v2·Nuclear Theory
Hints on the quadrupole deformation of the (1232)
C. Fernandez-Ramirez (Instituto de Estructura de la Materia, CSIC, Spain)🇪🇸 · E. Moya de Guerra (Departamento de Fisica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid, Spain)🇪🇸 · J.M. Udias (Departamento de Fisica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid, Spain)🇪🇸
Abstract
The E2/M1 ratio (EMR) of the (1232) is extracted from the world data in pion photoproduction by means of an Effective Lagrangian Approach (ELA).This quantity has been derived within a crossing symmetric, gauge invariant, and chiral symmetric Lagrangian model which also contains a consistent modern treatment of the (1232) resonance. The \textit{bare} s-channel (1232) contribution is well isolated and Final State Interactions (FSI) are effectively taken into account fulfilling Watson's theorem. The obtained EMR value, EMR%, is in good agreement with the latest lattice QCD calculations [Phys. Rev. Lett. 94, 021601 (2005)] and disagrees with results of current quark model calculations.
Comments: Enlarged conclusions and explanations on the E2/M1 ratio. Figure 3 improved. References updated. 5 pages. 3 figures. 2 tables. Accepted for publication in Physical Review C