Abstract
To compare theoretical predictions and experimental results, we require
not only a precise knowledge of the observables themselves, but also a good
understanding of the uncertainty introduced by missing higher orders in
perturbative QCD. In this work, we present a method which combines effective field theories and perturbative QCD to predict the effect of New Physics on measurements at the LHC and at other future colliders. We use heavy-quark, heavy-scalar and soft-collinear effective theory to calculate a three-body cascade decay at NLO QCD in the expansion-by-regions formalism. The second project focuses on theoretical uncertainties in perturbative QCD. We perform a study of theoretical uncertainties obtained using the traditional scale-variation and the Cacciari-Houdeau approach [1], which uses Bayesian statistics to estimate missing-higher-order uncertainties. In addition, we discuss an extension of the Cacciari-Houdeau approach to observables with hadrons in the initial state.