Chiral Dynamics in Photo-Pion Physics: Theory, Experiment, and Future Studies at the HI$\gamma$S Facility

Abstract

A review of photo-pion experiments on the nucleon in the near threshold region is presented. Comparisons of the results are made with the predictions of the low energy theorems of QCD calculated using chiral perturbation theory (ChPT) which is based on the spontaneous breaking of chiral symmetry as well as its explicit breaking due to the finite quark masses. As a result of the vanishing of the threshold amplitudes in the chiral limit, the experiments are difficult since the cross sections are small. Nevertheless the field has been brought to a mature stage of accuracy and sensitivity. The accomplishments and limitations of past experiments are discussed. Future planned experiments at Mainz and HI$\gamma$S using polarization observables are discussed as a more rigorous test of theoretical calculations. Emphasis is given to the technical developments that are required for the HI$\gamma$S facility. It is shown that future experiments will provide more accurate tests of ChPT and will be sensitive to isospin breaking dynamics due to the mass difference of the up and down quarks.

61 pages, 10 figures, 2 tables

References in corpus (7)

• Chiral Perturbation Theory and Baryon Properties
• Supersymmetric models with minimal flavour violation and their running
• Chiral perturbation theory
• Effective Lagrangian Approach to pion photoproduction from the nucleon
• Neutron-neutron scattering length from the reaction gamma d --> pi^+ nn employing chiral perturbation theory
• Test of isospin symmetry via low energy ${}^1$H(${\pi }^{-}$,${\pi }^o$)$n$ charge exchange
• Operator Approach to Isospin Violation in Pion Photoproduction

Cited by in corpus (9)

• Precision calculation of threshold pi^- d scattering, pi N scattering lengths, and the GMO sum rule
• Precision calculation of the pi^- deuteron scattering length and its impact on threshold pi-N scattering
• Isospin breaking in the pion-nucleon scattering lengths
• Model Selection for Pion Photoproduction
• Upper Energy Limit of Heavy Baryon Chiral Perturbation Theory in Neutral Pion Photoproduction
• Unexpected impact of D waves in low-energy neutral pion photoproduction from the proton and the extraction of multipoles
• Low-Energy D-Wave Effects in Neutral Pion Photoproduction
• Pion electroproduction in a nonrelativistic theory
• Neutral Pion Production in the Threshold Region