The e p -> e' p eta reaction at and above the S11(1535) baryon resonance

TL;DR

This paper reports new cross section measurements for the e p -> e' p eta reaction over a broad energy range, providing insights into baryon resonance properties, especially the S11(1535), through analysis of response functions and resonance interference.

Contribution

It presents new experimental data on eta production in electron-proton scattering, expanding the kinematic coverage and refining resonance photocoupling parameters.

Findings

Sharp structure at W ~ 1.7 GeV due to S and P wave interference

Refined photon coupling amplitude for S11(1535)

Evidence of resonance interference effects

Abstract

New cross sections for the reaction e p -> ep eta are reported for total center of mass energy W = 1.5--1.86 GeV and invariant momentum transfer Q^2 = 0.25--1.5 GeV^2. This large kinematic range allows extraction of important new information about response functions, photocouplings, and eta N coupling strengths of baryon resonances. Expanded W coverage shows sharp structure at W \~ 1.7 GeV; this is shown to come from interference between S and P waves and can be interpreted in terms of known resonances. Improved values are derived for the photon coupling amplitude for the S11(1535) resonance.