Study of $N(1520)$ and $N(1535)$ structures via $\gamma^*p\to N^*$ transitions

TL;DR

This study analyzes the electromagnetic transition helicity amplitudes of the $N(1520)$ and $N(1535)$ resonances using a constituent quark model, comparing theoretical predictions with experimental data to understand their quark structure.

Contribution

It provides a detailed theoretical analysis of the $N(1520)$ and $N(1535)$ resonances' helicity amplitudes within the constituent quark model, highlighting their primarily three-quark $L=1$ state composition.

Findings

Resonances are mainly three-quark $L=1$ states

Meson cloud contributions are unlikely to dominate at low $Q^2$

Theoretical results agree with experimental data on helicity amplitudes

Abstract

The helicity amplitudes of the $N(1520)$ and $N(1535)$ resonances in the $\gamma^*p\to N^*$ electromagnetic transition are studied in the constituent quark model using the impulse approximation, with the proton and resonances assumed to be in three-quark configurations. The comparison of theoretical results and experimental data on the helicity amplitudes $A_{1/2}$, $A_{3/2}$, and $S_{1/2}$ indicates that the $N(1520)$ and $N(1535)$ resonances are primarily composed of three-quark $L=1$ states but may contain additional components. However, it is improbable that contributions from meson clouds will be dominant at low $Q^2$.