PhD Thesis Defense by Laura Jenniches

Understanding Theoretical Uncertainties in Perturbative QCD Computations

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 my talk, I 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. I use the expansion-by-regions formalism to obtain an improved narrow-width approximation which can be applied to differential distributions. The second project focuses on theoretical uncertainties in perturbative QCD. I present a study of theoretical uncertainties obtained using the traditional scale-variation and the Cacciari-Houdeau approach, which uses Bayesian statistics to estimate missing-higher-order uncertainties. In addition, I discuss an extension of the Cacciari-Houdeau approach to observables with hadrons in the initial state.