Introduction to Soft-Collinear Effective Theory

Starting 20th September 2022 – every Tuesday and Thursday from 10-12 am in B1 – ending 13th October 2022

Precise theoretical predictions of processes at high-energy colliders, such as the CERN LHC, are crucial to search for new phenomena in particle physics. Perturbative QCD calculations often suffer from large logarithms of scale ratios, which invalidate a fixed-order perturbative expansion. Factorization theorems play an important role to understand observables sensitive to several different mass or distance scales. Soft-collinear effective theory (SCET) provides an efficient way to achieve factorization for observables sensitive to soft and collinear emission of massless partons, and facilitates the resummation of large logarithms to all orders in perturbative QCD.

This course introduces students to basic concepts of SCET and its applications to collider physics. The course will begin by setting up the effective Lagrangian and introducing the basic formalism, which is then used to derive factorization formulae for several collider observables. We then discuss computation methods to evaluate the relevant low-energy matrix elements. Practical techniques for solving renormalization-group equations and for resumming large logarithms will be also presented. If time permits, the course will also cover some advanced topics such as the rapidity renormalization group and infrared structure of QCD scattering amplitudes.

Learning results of the course:

The goal of this course is to offer students an opportunity to learn basic knowledge of SCET from several examples of factorization and resummation for collider observables. Specifically, they will learn practical tools to calculate scattering matrix elements in SCET at one-loop order and beyond, have a grasp of the techniques to perform resummation in momentum space, and know how to handle rapidity divergences. They will also have a basic understanding of recent developments in SCET. 


Zelong Liu