Photoproduction of eta mesons off protons for photon energies from 0.75 GeV to 3 GeV

TL;DR

This study measures total and differential cross sections for eta meson photoproduction off protons across photon energies from 0.75 to 3 GeV, revealing resonance structures and exchange mechanisms.

Contribution

It provides new experimental data on eta photoproduction, identifies a new resonance N(2070)D15, and analyzes the underlying reaction mechanisms.

Findings

Observation of 11 nucleon resonances decaying into p eta.

Evidence for a new resonance N(2070)D15 with specific mass and width.

Detection of a strong forward peak at energies above 1.5 GeV indicating vector meson exchange.

Abstract

Total and differential cross sections for the reaction p(gamma, eta)p have been measured for photon energies in the range from 750 MeV to 3 GeV. The low-energy data are dominated by the S11 wave which has two poles in the energy region below 2 GeV. Eleven nucleon resonances are observed in their decay into p eta. At medium energies we find evidence for a new resonance N(2070)D15 with (mass, width) = (2068+-22, 295+-40) MeV. At photon energies above 1.5 GeV, a strong peak in forward direction develops, signalling the exchange of vector mesons in the t channel.