Master thesis defence by Thor Rasmussen
Higgs Decay to Two Leptons and a Photon in the Standard Model Eective Field Theory
Time: November 22 at 13:00
Place: Auditorium A
Organizer: Tyler Corbett
Abstract: In this thesis we first introduce the concepts of the electroweak sector and the Higgs-mechanism in the standard model. We then discuss effective field theories where we introduce the four-Fermi theory as an example. We then discuss a simple method for deriving the effective action at tree-level from a ultraviolet theory. We also discuss how one might use effective field theories to infer the nature of new heavy physics and how these shift the predictions of low energy theories such as the standard model. Motivated by the discussion of effective field theories and how they can provide tools for exploring new physics, we discuss the standard model effective field theory (SMEFT).
Next we apply these concepts in order to study the Higgs decay to two leptons and a photon at tree and one-loop level in the standard model and the shifts to this from the SMEFT at tree-level. We then calculate the total decay width including the SMEFT contributions and expand this result in terms of the Wilson coefficients from the SMEFT. Finally, we study five regions in phase space which we use to demonstrate that the contributions of different operators within the SMEFT can be emphasized when using these regions and the aforementioned assumptions about new physics.