Diffractive Neutral Pion Production, Chiral Symmetry and the Odderon

Abstract

We discuss the diffractive photo- and electroproduction of a single neutral pion at high energies where it can occur due to odderon exchange. We show that this process is dynamically suppressed as a consequence of chiral symmetry. Our result reconciles earlier theoretical expectations with the non-observation of this reaction at HERA.

6 pages, based on invited talks given by C.E. at XVth International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS 2007), Munich, April 2007, and by O.N. at 12th International Conference on Elastic and Diffractive Scattering (EDS07), DESY Hamburg, May 2007