On the Photoproduction Reactions $\gamma d\to\pi NN$

TL;DR

This paper reviews theoretical models of incoherent pion photoproduction on deuterons, analyzing recent experimental data, accounting for final state interactions, and extracting neutron reaction properties to improve understanding of baryon resonances.

Contribution

It introduces a procedure to extract neutron reaction cross sections from deuteron data, considering final state interactions, and provides improved electromagnetic properties of baryon resonances.

Findings

Analysis of recent CLAS, A2, and PION@MAX-lab data.

Extraction of $ ext{γ}n o ext{π}N$ differential cross sections.

Improved understanding of baryon $N^*$ resonance properties.

Abstract

A review of our works providing a theoretical description of incoherent pion photoproduction on the deuteron is presented. The existing $\gamma d\to\pi NN$ data are analysed, especially those obtained more recently by the CLAS Collaboration at JLab, the A2 Collaboration at MAMI at Mainz, and the PION@MAX-lab Collaboration at Lund. A procedure, which accounts for the final state interactions (FSI), is applied to extract $\gamma n\to\pi N$ differential cross sections from the deuteron data. The role of FSI is discussed. We also comment on the results of other works in connection with some discrepancies seen in comparing the model with experiment. The electromagnetic properties of baryon $N^\ast$ resonances, improved using the extracted $\gamma n\to\pi N$ differential cross sections, are presented. A model description of the cross section data from charged-pion photoproduction reactions $\gamma d\to\pi^{\pm}NN$ near threshold is also given. The $\gamma d\to\pi^-pp$ data are used to extract the $E_{0+}$ multipole and total crsoss sections of the reaction $\gamma n\to\pi^-p$ near threshold.