2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/133299We 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 2007High Energy Physics - Phenomenologytext