Measurement of the double polarisation observable G in single pseudoscalar meson photoproduction

TL;DR

This paper reports the measurement of the double polarisation observable G in single pseudoscalar meson photoproduction, providing data crucial for partial wave analysis of nucleon resonances.

Contribution

It presents the first measurement of the G asymmetry with linearly polarised photons and longitudinally polarised protons in pion and eta photoproduction.

Findings

Measurement of the G asymmetry in pion and eta channels

Provides data for partial wave analysis of nucleon resonances

Enhances understanding of nucleon excitation spectrum

Abstract

The excitation spectrum of the nucleon consists of several overlapping resonances. To identify these resonances and their contributions to the measured cross sections, a partial wave analysis is used. A set of at least eight, well chosen, single and double polarisation observables is needed to derive an unambiguous solution. With the Crystal Barrel/TAPS setup at ELSA, single and double polarisation observables can be measured in different reaction channels, by using the combination of a linearly or circularly polarised photon beam and a longitudinally or transversely polarised butanol frozen spin target. Results of the G asymmetry measurement, using linearly polarised photons and longitudinally polarised protons, for pion and eta photoproduction are presented. This project is supported by the DFG (SFB/TR16).