In this paper we show how gauge symmetries in an effective theory can be used to simplify proofs of factorization formulas in highly energetic hadronic processes. We use the soft-collinear effective theory, generalized to deal with back-to-back jets of collinear particles. Our proofs do not depend on the choice of a particular gauge, and the formalism is applicable to both exclusive and inclusive factorization. As examples we treat the $\pi -\gamma$ form factor $(\gamma {\gamma }^{*}\to {\pi }^0),$ light meson form factors $\left({\gamma }^{*}\overrightarrow{M}M\right),$ as well as deep inelastic scattering ${(e}^{-}\overrightarrow{p}{e}^{-}X),$ the Drell-Yan process $(p\overline{p}\to {\mathrm{Xl}}^{+}{l}^{-}),$ and deeply virtual Compton scattering $\left({\gamma }^{*}\overrightarrow{p}{\gamma }^{\left(*\right)}p\right).\mathrm{}$

• Received 5 March 2002

DOI:https://doi.org/10.1103/PhysRevD.66.014017