Effective Field Theory Beyond the Standard Model

Starting week 45, 2023 – every Tuesday from 10am - 12pm in room B1 – ending week 51, 2023

The absence of any new high-energy resonances beyond the Higgs boson at the Large Hadron Collider suggests the presence of a mass gap up to the scale of new physics, whatever it might be. Despite this possible gap, we can look for hints of new physics in various precision measurements, which can probe much higher energy scales than what can be realized on shell in current experiments. The Standard Model Effective Field Theory (SMEFT) is a very useful framework for interrogating such effects of new high-energy physics on experiments at lower energies.

This course introduces the SMEFT as an important tool in the search for physics beyond the SM. We will begin by covering the basic ideas behind using Effective field theories (EFTs) and outline their use in the pipeline between high-energy physics models and predictions for low-energy observables. We will then proceed to cover the two main uses of the SMEFT: In the so-called "bottom-up" approach, the SMEFT is used to parametrize possible deviations from the SM, which can be used to search for consistent beyond-the-SM (BSM) explanations for experimental anomalies and inform model building. The "top-down" application of SMEFT lies in the computation of low-energy observables from high-scale BSM models. This is easier when using SMEFT because one can reuse part of the computations. At the same time, using an EFT approach is required for obtaining accurate results.

To illustrate the SMEFT use cases, we will draw on real-world examples from recent literature. Along the way, we will discuss the importance of the renormalization group and discuss how to perform EFT matching beyond the leading order in the perturbative expansion. The ideas and techniques taught in this course are under continual development in the BSM community and seem certain to play an important role in BSM phenomenology for the foreseeable future.

Learning results of the course:

The objective of this course is to provide the students with a detailed understanding of the role of effective field theories in physics beyond the Standard Model. A particular emphasis will be put on the role of the renormalization group effects and their calculation using perturbation theory. The participants will learn what goes into the EFT workflow and how to connect high-energy new physics with low-energy observables.


Anders Eller Thomsen