Initial-state radiation at LEP energies and the corrections to Higgs boson production

It is shown that for e⁺e^? scattering processes described by the exchange of one photon or vector boson the O(α) radiative corrections to the initial state completely factorize the lowest-order cross section. This factorization holds for both hard and soft (or virtual) photons. We present a formalism for applying these radiative corrections in a process-independent way, and described the corresponding computer program. As an application we study the initial-state radiative corrections to the Higgs production processes e⁺e^? → μ⁺μ^?H and e⁺e^? → e⁺e^?H.