Precision fits for the LHC and beyond

Thesis

In this thesis we consider the phenomenology of Quantum Chromodynamics (QCD) and the Standard Model Effective Field Theory (SMEFT), with reference to the ongoing experiments at the Large Hadron Collider (LHC). Our emphasis is on constraining free parameters of the theories, such that the precision of theoretical calculations for the LHC are able to match the high level of experimental precision now available.

To this end, we discuss two fitting frameworks which aim to be robust and reliable ways to extract these free parameters of QCD and the SMEFT. In QCD we wish to extract the strong coupling constant at the mass of the Z boson, α_s(M_Z), and in the SMEFT we want to constrain the free parameters of the theory which allow for deviations from the Standard Model.

We will first introduce QCD and the SMEFT and theoretically motivate our studies. We then move on to introduce the fitting framework used to extract the strong coupling constant. We will use parton distribution functions (PDFs) to determine the strong coupling; PDFs themselves must also be extracted from data, and their determination introduces many sources of methodological uncertainties which can propagate into our determination of α_s(M_Z). We will discuss the tools developed in order to quantify these uncertainties and obtain a reliable estimate of α_s(M_Z).

In the second part of this thesis, we will discuss a novel framework developed to determine the free parameters of the SMEFT. Initially we will motivate and outline the new methodology, which we denote SMEFiT, and then apply the framework to a detailed analysis of the top sector at the LHC.

Authors: Slade, E

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: QCD; LHC physics; SMEFT
• Subjects: Quantum chromodynamics