Pions: Experimental Tests of Chiral Symmetry Breaking

Understand

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 $\pi\pi$ scattering, pion properties, $\pi$N scattering and electromagnetic pion production.
• These predictions have been shown to be consistent with QCD in the meson sector by increasingly accurate lattice calculations.