Gauge Invariance and Factorisation in Exclusive Meson Production

Abstract

The structure of the nonperturbative vector meson vertex function complicates the proof of the factorisation theorem for the reaction ${\gamma }^{\ast }p\to Vp$. It leads to additional contributions but, in a simple model for the vertex function, gauge invariance ensures that they cancel and factorisation is preserved.

Comments: 11 pages LaTeX, 4 figures included, uses epsf