Pion Observables and QCD
  The nonperturbative, Dyson-Schwinger equation approach to solving QCD provides a straightforward, microscopic description of dynamical chiral symmetry breaking and confinement. It is an ideal tool for the study of pion observables. This is illustrated via its application to the calculation of: the $\pi$-$\pi$ scattering lengths $a_0^0$, $a_0^2$, $a_1^1$, $a_2^0$, $a_2^2$ and associated partial wave amplitudes; the $\pi^0\rightarrow \gamma\gamma$ decay width; and the charged pion form factor, $F_\pi(q^2)$. 
Craig D. Roberts