Infrared structure of gauge theory amplitudes provides vital glue to resum soft gluons to all orders in perturbation theory to make sensible predictions. We demonstrate how resummation of threshold logarithms can be done using the universality of IR singularities and factorisation properties of scattering cross sections. Using the property of Casimir scaling of soft gluon contributions to Drell-Yan and Higgs productions we predict third order threshold QCD corrections to inclusive cross section as well as rapidity distribution of pair of leptons in DY process.
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