Based on the spontaneous breaking of chiral symmetry, chiral perturbation
theory (ChPT) is believed to approximate confinement scale QCD. Dedicated and
increasingly accurate experiments and improving lattice calculations are
confirming this belief, and we are entering a new era in which we can test
confinement scale QCD in some well chosen reactions. This is demonstrated with
an overview of low energy experimental tests of ChPT predictions of ππ
scattering, pion properties, πN scattering and electromagnetic pion
production. These predictions have been shown to be consistent with QCD in the
meson sector by increasingly accurate lattice calculations. At present there is
good agreement between experiment and ChPT calculations, including the ππ
and πN s wave scattering lengths and the π0 lifetime. Recent,
accurate pionic atom data are in agreement with chiral calculations once
isospin breaking effects due to the mass difference of the up and down quarks
are taken into account, as was required to extract the ππ scattering
lengths. In addition to tests of the theory, comparisons between ππ and
Ï€N interactions based on general chiral principles are discussed. Lattice
calculations are now providing results for the fundamental, long and
inconclusively studied, πN σ term and the contribution of the
strange quark to the mass of the proton. Increasingly accurate experiments in
electromagnetic pion production experiments from the proton which test ChPT
calculations (and their energy region of validity) are presented. These
experiments are also beginning to measure the final state πN interaction.
This paper is based on the concluding remarks made at the Chiral Dynamics
Workshop CD12 held at Jefferson Lab in Aug. 2012.Comment: 13 pages, 8 fig