Eur. Phys. J. C (2007) 49: 685-696
https://doi.org/10.1140/epjc/s10052-006-0082-9

Regular Article - Theoretical Physics

Chiral symmetry and diffractive neutral pion photo- and electroproduction

¹ ECT*, Strada delle Tabarelle 286, 38050, Villazzano (Trento), Italy
² Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, 69120, Heidelberg, Germany

^* e-mail: Ewerz@ect.it

Received: 14 August 2006
Published online: 18 November 2006

Abstract

We show that diffractive production of a single neutral pion in photon-induced reactions at high energy is dynamically suppressed due to the approximate chiral symmetry of QCD. These reactions have been proposed as a test of the odderon-exchange mechanism. We show that the odderon contribution to the amplitude for such reactions vanishes exactly in the chiral limit. This result is obtained in a nonperturbative framework and by using PCAC relations between the amplitudes for neutral pion and axial vector current production.