Leading large-x logarithms of the quark–gluon contributions to inclusive Higgs-boson and lepton-pair production

We present all-order expressions for the leading double-logarithmic threshold contributions to the quark–gluon coefficient functions for inclusive Higgs-boson production in the heavy top-quark limit and for Drell–Yan lepton-pair production. These results have been derived using the structure of the unfactorized cross sections in dimensional regularization and the large-x resummation of the gluon–quark and quark–gluon splitting functions. The resummed coefficient functions, which are identical up to colour factor replacements, are similar to their counterparts in deep-inelastic scattering but slightly more complicated.