Threshold π– photoproduction and Compton scattering on the deuteron

Q Science (General);QC Physics

Strandberg, Bruno ; MacGregor, Douglas

University:University of Glasgow

Department:School of Physics and Astronomy

关键词: Pion photoproduction, Compton scattering, neutron polarisabilities, active helium target, deuteron target, pion threshold, hadron physics, final state interactions, chiral perturbation theory.;   

Others  :  http://theses.gla.ac.uk/8362/7/2017StrandbergPhD.pdf

来源: University of Glasgow

【 摘 要 】

Over the years various theoretical frameworks have been developed to gain insight into the strong force at the hadronic scale and several of them make predictions for the pion photoproduction cross-section at threshold. The cross-sections for positive and neutral pion photoproduction have been measured, but experimental data on the negative pion has so far been absent. The first measurement of the cross-section σ(E) for π− photoproduction on the deuteron near threshold is presented. The π− cross-section provides a test for the theoretical models that aim to describe Quantum Chromodynamics in the non-perturbative regime.Nucleon polarisabilities are long range nucleon structure observables and give insight into the internal degrees of freedom of the nucleon. The proton polarisabilities are determined significantly more accurately compared to the neutron polarisabilities. The latter can be extracted from the differential cross-section for Compton scattering on the deuteron. The first measurement of the differential cross-section dσ/dΩ(E, cos θ) for Compton scattering on the deuteron as a function of photon energy (E) and polar angle (θ) above the pion threshold is presented. The new experimental data contributes to the ongoing effort for accurate determination of the neutron polarisabilities.Due to recent theoretical advances the differential cross-section for Compton scattering on Helium-3 can now also be interpreted in a way that allows extraction of the neutron polarisabilities. In the appendix a proposed experiment to measure the differential cross-section for Compton scattering on Helium-3 with a Helium Gas Scintillator Active target is considered.