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Photoproduction of Etas and N$^*$(1535) Electrostrong Properties

Nimai C. Mukhopadhyay·J. -F. Zhang·M. Benmerrouche
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Abstract

From the new Mainz data of eta photoproduction off protons\cite{ref1} and deuterons\cite{ref2}, we can extract, via the effective Lagrangian approach (ELA)\cite{ref3}, the electrostrong parameters $ξ_{p}$ and $ξ_{n}$ for the N$^*$(1535) excitation. These parameters are, in units of $10^{-4} MeV^{-1}$, $(2.20\pm 0.15)$ and $(-1.86\pm 0.20)$ respectively. They yield the ratio of the helicity amplitudes for the excitation of N$^*$(1535) by photons off neutrons and protons to be $A^{n}_{1/2}/A^{p}_{1/2}=-0.84\pm 0.15$, a quantity of fundamental importance in the baryon structure. Best estimates in the quark model are close to this ratio.

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Nimai C. Mukhopadhyay, J. -F. Zhang, M. Benmerrouche. 1995-11-01. Photoproduction of Etas and N$^*$(1535) Electrostrong Properties. https://arxiv.org/abs/nucl-th/9511001

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