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Hints on the quadrupole deformation of the Δ(1232)

C. Fernandez-Ramirez, E. Moya de Guerra, J. M. Udias

nucl-tharXiv:nucl-th/0601037

Abstract

The E2/M1 ratio (EMR) of the Δ(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 Δ(1232) resonance. The bare s-channel Δ(1232) contribution is well isolated and Final State Interactions (FSI) are effectively taken into account fulfilling Watson's theorem. The obtained EMR value, EMR=(-1.300.52)%, 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.

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