The Sudakov form factor beyond the leading logarithmic approximation

We present the general form of the asymptotic behavior of the massless electron-photon vertex function in quantum electrodynamics in the limit where q2, the virtual mass of the photon, becomes large. All the logarithms in q2 are taken into account, whereas inverse powers of q2 are neglected. In contradistinction to previous investigations we consider the off-shell vertex function and work in the Feynman gauge. Extensive use is made of the α-representation of Feynman integrals. (orig.)