Study of the gp-->etap reaction with the Crystal Ball detector at the Mainz Microtron(MAMI-C)

TL;DR

This study measures the gamma-proton to eta-proton reaction using the Crystal Ball detector at MAMI-C, providing detailed cross sections and revealing a dip near 1680 MeV, enhancing understanding of reaction dynamics.

Contribution

It offers the first high-statistics, differential cross section data for the gamma-proton to eta-proton reaction over a broad energy and angular range, improving partial-wave analyses.

Findings

Identified a dip at W = 1680 MeV in total cross section.

Provided detailed differential cross sections across 120 energy bins.

Compared data with existing SAID and MAID models, refining reaction understanding.

Abstract

The gp-->etap reaction has been measured with the Crystal Ball and TAPS multiphoton spectrometers in the energy range from the production threshold of 707 MeV to 1.4 GeV (1.49 =< W >= 1.87 GeV). Bremsstrahlung photons produced by the 1.5-GeV electron beam of the Mainz Microtron MAMI-C and momentum analyzed by the Glasgow Tagging Spectrometer were used for the eta-meson production. Our accumulation of 3.8 x 10^6 gp-->etap-->3pi0p-->6gp events allows a detailed study of the reaction dynamics. The gp-->etap differential cross sections were determined for 120 energy bins and the full range of the production angles. Our data show a dip near W = 1680 MeV in the total cross section caused by a substantial dip in eta production at forward angles. The data are compared to predictions of previous SAID and MAID partial-wave analyses and to thelatest SAID and MAID fits that have included our data.