HIGH-ENERGY FACTORIZATION AND SMALL-X DEEP-INELASTIC SCATTERING BEYOND LEADING ORDER

High-energy factorization in QCD is investigated beyond leading order and its relationship to the factorization theorem of mass singularitie s is established to any collinear accuracy. Flavour non-singlet observ ables are shown to be regular at small x order by order in perturbatio n theory. In the singlet sector, we derive the relevant master equatio ns for the space-like evolution of gluons and quarks. Their solution e nables us to sum next-to-leading corrections to the small-x behaviour of quark anomalous dimensions and deep inelastic scattering coefficien t functions. We present results in both <(MS)over bar> and DIS factori zation schemes.