Neutral Pion Production in the Threshold Region

Abstract

We give an overview of the physics motivation and evolution of the neutral pion photoproduction measurements in the threshold region conducted in the A2 collaboration at MAMI. The latest two experiments have been performed with the almost 4-pi Crystal Ball detector. The first was with a linearly polarized photon beam and unpolarized liquid-hydrogen target. The data analysis is now complete and the linearly polarized beam asymmetry along with differential cross sections provide the most stringent test to date of the predictions of Chiral Perturbation Theory and its energy region of convergence. More recently a measurement was performed using both circularly polarized photons and a transversely polarized butanol frozen-spin target, with the goal of extracting both the target and beam-target asymmetries. From these we intend to extract pi-N scattering sensitive information for the first time in photo-pion reactions. This will be used to test isospin conservation and further test dynamics of chiral symmetry breaking in QCD as calculated at low energies by Chiral Perturbation Theory.

8 pages, 5 figures, submitted to EPJ Special Topics as part of the proceedings of the Conclusive Symposium of Collaborative Research Centre 443

References in corpus (8)

• Unitary Isobar Model - MAID2007
• Review of lattice results concerning low energy particle physics
• Chiral Perturbation Theory and Baryon Properties
• Chiral perturbation theory
• Isospin breaking in Kl4 decays
• Isospin breaking in the pion-nucleon scattering lengths
• Low-Energy D-Wave Effects in Neutral Pion Photoproduction
• Operator Approach to Isospin Violation in Pion Photoproduction

Cited by in corpus (2)

• Upper Energy Limit of Heavy Baryon Chiral Perturbation Theory in Neutral Pion Photoproduction
• Consistent threshold pi0 electro-production at Q^2=0.05, 0.10, and 0.15 GeV^2/c^2