Unstable particles, gauge invariance and the Delta⁺⁺ resonance parameters

2003/02/24 by G. Lopez Castro, A. Mariano
Physics and Astronomy · #hep-ph #nucl-ex #nucl-th

paper · pdf

published as Found.Phys. 33 (2003) 719-734 · 16 pages, 2 figures, Talk given at Zacatecas Forum in Physics, May 11-13, 2002, Zacatecas Mexico

arxiv created 2003/02/24 · arxiv updated 2009/11/30

Abstract

The elastic and radiative pion(+)-proton scattering are studied in the framework of an effective Lagrangian model for the Delta⁺⁺ resonance and its interactions. The finite width effects of this spin-3/2 resonance are introduced in the scattering amplitudes through a complex mass scheme to respect electromagnetic gauge invariance. The resonant pole (Delta⁺⁺) and background contributions (rho⁰, sigma, Delta and neutron states) are separated according to the principles of the analytic S-matrix theory. The mass and width parameters of the Δ⁺⁺ obtained from a fit to experimental data on the total cross section are in agreement with the results of a model-independent analysis based on the analytic S-matrix approach. The magnetic dipole moment determined from the radiative pion-proton scattering is mu_Delta⁺⁺=(6.14 +/- 0.51) nuclear magnetons.

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