"The first runs of the Large Hadron Collider (LHC) experiment just finished. The LHC was successful in discovering a particle compatible with the Higgs boson of the Standard Model (SM). However expectations to discover New Physics have not been met so far.In order to establish whether the new resonance is the SM Higgs boson, or not, precise measurements of its properties are mandatory. These require accurate predictions for cross-sections involving the Higgs boson, as well as for SM backgrounds, that need to be subtracted accurately. Furthermore, since so far New Physics has been elusive, it will be even more important to extend the range of these searches as much as possible. This requires a solid control of SM backgrounds.This project aims at pushing the frontier of precision QCD calculations to reach an unprecedented precision for colliderprocesses. The project is divided into two main parts.In the first part the PI will formulate a general procedure to merge different calculations at next-to-leading order (NLO) level. This will lead to the construction of an event generator for two-to-one and two-to-two scattering processes at next-to-next-to-leading order (NNLO), including parton shower corrections, essentially upgrading the POWHEG NLO generator to the NNLO level. Depending on the process considered, a significant reduction of the theoretical errors, by a factor 2-4, will be achieved.The second part focuses on extending the accuracy of resummed predictions for important QCD observables from next-to-leading logarithmic to next-to-next-to-leading logarithmic level, again achieving a substantial reduction of the theoretical error. The observables considered include, besides event-shapes and jet-rates, also jet-veto predictions in Higgs + 1 or 2 jet events.Besides the groundbreaking impact on present LHC physics measurements, these results will also be essential to match the high accuracy of measurements at a future linear collider."