Empirical parametrizations of the resonance amplitudes based on the Siegert's theorem

Abstract

We present parametrizations of the ${\gamma }^{\ast }N\to N(1535)1/2^{-}$, ${\gamma }^{\ast }N\to N(1520)3/2^{-}$ and ${\gamma }^{\ast }N\to \Delta (1232)3/2^{+}$ transition amplitudes that are compatible with the analytic constraints at the pseudothreshold (Siegert's theorem). The presented parametrizations also provide a fair description of the experimental data. For the case of the ${\gamma }^{\ast }N\to \Delta (1232)3/2^{+}$ transition, we discuss how the pion cloud parametrizations of the electric and the Coulomb quadrupole form factors can be adjusted according to the Siegert's theorem.

arXiv commentProceedings of the "The 14th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon". July 25-30, 2016, Kyoto, Japan. 5 pages, 4 figures

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