Extracting the photoproduction cross section off the neutron gn-->pi-p from deuteron data with FSI effects

TL;DR

This paper develops a theoretical method to extract the neutron photoproduction cross section from deuteron data by accounting for final state interaction effects, improving accuracy over impulse approximation.

Contribution

It introduces a reliable FSI correction procedure to determine the elementary gn-->pi-p cross section from deuteron data, incorporating realistic NN- and piN-FSI amplitudes.

Findings

FSI effects are significant at small angles, especially near zero degrees.

The correction factor R approaches unity at larger angles, indicating minimal FSI influence.

The method aligns with Glauber approach estimations at higher energies.

Abstract

The incoherent pion photoproduction reaction gd-->pi-pp is considered theoretically in a wide energy region Eth =< Eg =< 2700 MeV. The model applied contains the impulse approximation as well as the NN- and piN-FSI amplitudes. The aim of the paper is to study a reliable way for getting the information on elementary gn-->pi-p reaction cross section beyond the impulse approximation for gd-->pi-pp. For the elementary gN-->piN, NN-->NN, and piN-->piN amplitudes, the results of the GW DAC are used. There are no additional theoretical constraints. The calculated cross section dSigma/dOmega(gd->pi-pp) are compared with existing data. The procedure used to extract information on the differential cross section dSigma/dOmega(gn-->pi-p) on the neutron from the deuteron data using the FSI correction factor R is discussed. The calculations for R versus pi-p CM angle \theta_1 of the outgoing pion are performed at different photon-beam energies with kinematical cuts for "quasi-free" process gn-->pi-p. The results show a sizeable FSI effect R \neq 1 from S-wave part of pp-FSI at small angles close to \theta_1 ~ 0: this region narrows as the photon energy increases. At larger angles, the effect is small (|R-1|<<1) and agrees with estimations of FSI in the Glauber approach.