Valence quark contributions for the gamma N -> P11(1440) form factors

TL;DR

This study estimates valence quark contributions to the gamma N -> P11(1440) transition form factors using a covariant spectator quark model, aligning with experimental and lattice QCD data at high Q2, and assesses meson cloud effects at low Q2.

Contribution

It introduces a parameter-free covariant spectator quark model to analyze the P11(1440) resonance form factors, integrating valence quark and meson cloud contributions.

Findings

Valence quark contributions match experimental data at high Q2.

Meson cloud effects are significant at low Q2.

Model requires no additional parameters beyond previous nucleon studies.

Abstract

Using a covariant spectator quark model we estimate valence quark contributions to the F1*(Q2) and F2*(Q2) transition form factors for the gamma N -> P11(1440) reaction. The Roper resonance, P11(1440), is assumed to be the first radial excitation of the nucleon. The present model requires no extra parameters except for those already fixed by the previous studies for the nucleon. Our results are consistent with the experimental data in the high Q2 region, and those from lattice QCD. We also estimate the meson cloud contributions, focusing on the low Q2 region, where they are expected to be dominant.