How accurate is the local-duality model for the pion elastic form factor?

Abstract

We study the accuracy of the pion form factor, obtained with a local-duality version of dispersive sum rules. To probe this accuracy, we make use of a potential model, where the exact form factor may be calculated from the solution of the Schroedinger equation and confronted with the local-duality form factor. The deviation between these quantities is found to be below 20% in the region of momentum transfers Q > 2 - 3 GeV, independently of the specific form of the confining potential. We argue that the local-duality model for elastic form factors in QCD has at least this level of accuracy.