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Hints on the quadrupole deformation of the $Δ$(1232)

C. Fernandez-Ramirez·E. Moya de Guerra·J. M. Udias
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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 \textit{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$=(-1.30\pm0.52)$%, 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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C. Fernandez-Ramirez, E. Moya de Guerra, J. M. Udias. 2006-04-18. Hints on the quadrupole deformation of the $Δ$(1232). https://doi.org/10.1103/physrevc.73.042201

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