Determination of the pion distribution amplitude

Understand

Right now, we have not enough knowledge to determine the hadron distribution amplitudes (DAs) which are universal physical quantities in the high energy processes involving hadron for applying pQCD to exclusive processes.

• Even for the simplest pion, one can't discriminate from different DA models.
• Inversely, one expects that processes involving pion can in principle provide strong constraints on the pion DA.
• For example, the pion-photon transition form factor (TFF) can get accurate information of the pion wave function or DA, due to the single pion in this process.