Study of $N(1440)$ structure via $\gamma^*p\to N(1440)$ transition

TL;DR

This paper investigates the internal structure of the $N(1440)$ resonance using quark models and compares theoretical predictions with experimental data to determine its dominant wave function configuration.

Contribution

It introduces a comparative analysis of different wave function models for $N(1440)$ and identifies the most consistent structure with experimental helicity amplitudes.

Findings

$N(1440)$ is mainly a $q^3$ first radial excitation.

Theoretical helicity amplitudes agree with experimental data for this configuration.

Different wave function models are evaluated against experimental results.

Abstract

We study the photoproduction of the $N(1440)$ resonance in $\gamma^*p\to N^*$ process in quark models, where the $N(1440)$ takes different wave functions: first radial excitation of the nucleon imported from low-lying baryon mass spectrum calculations, a general radial excitation of the nucleon, and a $q^3$ state with positive parity. The comparison between the theoretical results and experimental data on the helicity amplitudes $A_{1/2}$ and $S_{1/2}$ and the analysis of the spatial wave function of the $N(1440)$ resonance reveal that the $N(1440)$ resonance is mainly the $q^3$ first radial excitation.