Polarizabilities of the nucleon and spin dependent photo-absorption

TL;DR

This paper investigates nucleon polarizabilities and spin-dependent photo-absorption using recent experimental data and resonance models, providing detailed contributions and comparisons with theoretical predictions.

Contribution

It offers a comprehensive analysis of nucleon polarizabilities based on recent amplitude data and resonance couplings, including detailed cross section comparisons and quark model insights.

Findings

Agreement with recent MAMI and ELSA data on cross section differences

Quantitative contributions of s-channel and t-channel processes

Comparison of radiative widths with quark model predictions

Abstract

The polarizabilities $\alpha$ (electric), $\beta$ (magnetic) and $\gamma_\pi$ (backward spin) of the nucleon are investigated in terms of degrees of freedom of the nucleon using recent results for the CGLN amplitudes and resonance couplings $A_{1/2}$ and $A_{3/2}$. The photon excitation strengths of the excited states are given in terms of partial integrated photoabsorption cross sections and resonant contributions of the Gerasimov-Drell-Hearn (GDH) sum rule. As a test of the present predictions, cross section differences $(\sigma_{3/2}-\sigma_{1/2})$ of the excited states are compared with data recently measured at MAMI (Mainz) and ELSA (Bonn), In order to explain differences between proton and neutron, radiative widths of the excited states are compared with nonrelativistic and relativistic predictions based on the SU(6) harmonic oscillator (HO) quark model, A complete list of partial contributions from the s-channel and the $t$-channel are given for the polarizabilities.