On the physical Relevance of the Study of gamma* gamma -> pi0 pi0 at small t and large Q2

Abstract

We discuss the relevance of a dedicated measurement of exclusive production of a pair of neutral pions in a hard gamma* gamma scattering at small momentum transfer. In this case, the virtuality of one photon provides us with a hard scale in the process, enabling us to perform a QCD calculation of this reaction rate using the concept of Transition Distribution Amplitudes (TDA). Those are related by sum rules to the pion axial form factor F^pi_A and, as a direct consequence, a cross-section measurement of this process at intense beam electron-positron colliders such as CLEO, KEK-B and PEP-II, or Super-B would provide us with a unique measurement of the neutral pion axial form factor F^pi0_A at small scale.

Invited talk at Photon 2009: International Conference On The Structure And Interactions Of The Photon: 18th International Workshop On Photon-Photon Collisions: International Workshop On High Energy Photon Linear Colliders, 11-15 May 2009, Hamburg, Germany. 7 pages, 3 figures, LaTeX, uses desyproc.cls (provided)