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PHY578 Effective Field Theories for Particle Physics

General Information

Lecturer:

Prof. Peter Stoffer ( Y15 H82D and PSI )

Assistants:

David Radic ( PSI )

Lecture: Tuesday, 13:45 - 15:30, room HCI D 2 at ETH
Exercises: Tuesday, 15:45 - 16:30, room HCI D 2 at ETH
Module code: PHY578, 402-0845-61L
ECTS Credits: 6

Description

This course covers the basic concepts of effective field theories (EFTs) and dispersion theory. We will start by introducing the core concept of constructing EFTs and apply them to the low-energy description of the weak interaction and the effective description of heavy physics beyond the Standard Model. We will discuss Chiral Perturbation Theory (ChPT), the low-energy effective theory of Quantum Chromodynamics (QCD). We will also briefly discuss the application of this concept to describe a class of theories beyond the SM in which the SM Higgs arises as a composite state of a new confining sector.

The last part of the course is on dispersion theory and its interplay with EFTs. We will discuss how to make use of the constraints from unitarity of the S-matrix and analyticity of scattering amplitudes, in order to extend the range of validity of the theoretical description compared to pure EFT methods. We will also discuss how to obtain constraints on EFT parameters from unitarity and analyticity.

Main topics:

  • Introduction to Effective Field Theories
  • Decoupling and matching
  • Renormalization-group resummation
  • The Standard Model Effective Field Theory (SMEFT)
  • Chiral Lagrangians
  • Unitarity of the S-matrix
  • Analyticity and dispersion relations

Lecture notes

The following lecture notes will be updated weekly in the course of the semester.

EFT lecture notes (updated 01.09.2025) (PDF, 961 KB)

Lecture details

Lecture

Date

Topics covered

Lecture notes

Lecture 1

16.09.2025

Introduction, general principles

Sects. 1, 2.1, 2.2

Lecture 2

23.09.2025

Operator bases, EOM

 

Lecture 3

30.09.2025

Renormalization, running, tree-level matching

 

Lecture 4

07.10.2025

One-loop matching; Q&A section 2

 

Lecture 5

14.10.2025

Fermi theory

 

Lecture 6

21.10.2025

Fierz relations, operator mixing, scheme dependence

 

Lecture 7

28.10.2025

Chiral symmetry, SSB, Goldstone's theorem

 

Lecture 8

04.11.2025

CCWZ, explicit symmetry breaking, spurions

 

Lecture 9

11.11.2025

Chiral power counting, chiral Lagrangian at NLO

 

Lecture 10

18.11.2025

ChPT at one loop

 

Lecture 11

25.11.2025

SMEFT

 

Lecture 12

02.12.2025

SMEFT/LEFT; nonlinear realization of EW symmetry

 

Lecture 13

09.12.2025

Unitarity and analyticity

 

Lecture 14

16.12.2025

Dispersion relations and EFTs

 

 

Problem sets

Problem sheet Topics Discussed on Solutions

 

Dimensional regularization, renormalization

16./23.09.2025

 

Recordings

The course is organized as on-campus lecture only, without remote option. Recordings of the fall 2021 lectures can be found on SWITCHcast.

Suggested references