  We prove the all-order exponentiation of soft logarithmic corrections to
prompt photon production in hadronic collisions, by generalizing an approach
previously developed in the context of Drell-Yan production and deep-inelastic
scattering. We show that all large logs in the soft limit can be expressed in
terms of two dimensionful variables, and we use the renormalization group to
resum them. The resummed results that we obtain are more general though less
predictive than those proposed by other groups, in that they can accommodate
for violations of Sudakov factorization.
