Photoproduction of Neutral Pions off Protons

TL;DR

This study measures the differential cross sections for neutral pion photoproduction off protons across a broad energy range, including very forward angles, revealing high-mass nucleon resonances through partial-wave analysis.

Contribution

It provides the first differential cross section data in the very forward region for this reaction and identifies high-mass resonances using a partial-wave analysis.

Findings

Observation of differential cross sections at very forward angles.

Identification of high-mass resonances G_{17}(2190), D_{13}(2080), D_{15}(2070).

Enhanced understanding of nucleon excitation spectrum.

Abstract

Photoproduction of neutral pions has been studied with the CBELSA/TAPS detector in the reaction $\gamma p\to p\pi^0$ for photon energies between 0.85 and 2.50 GeV. The $\pi^0$ mesons are observed in their dominant neutral decay mode: $\pi^0\to\gamma\gamma$. For the first time, the differential cross sections cover the very forward region, $\theta_{\rm c.m.}<60^\circ$. A partial-wave analysis of these data within the Bonn-Gatchina framework observes the high-mass resonances $G_{17}$(2190), $D_{13}$(2080), and $D_{15}$(2070).