Quark mass dependence of $\gamma^{*}\pi\rightarrow\pi\pi$

Understand

Usually the simulation of scattering processes in lattice QCD is carried out at unphysically high values of the quark masses.

• Hence, a method to extrapolate data obtained in lattice calculations to physical masses is needed to allow for comparison between theory and experiment.
• To obtain a sound extrapolation, dispersion relations and chiral perturbation theory can be invoked.
• While a simple combined approach known as the inverse amplitude method allows for a successful extrapolation of $\pi\pi\to\pi\pi$ data, a more complicated framework is needed for inelastic processes such as $\gamma^{*}\pi\to\pi\pi$.