Chiral perturbation theory - Success and challenge

TL;DR

This paper reviews the successes and challenges of chiral perturbation theory in describing low-energy strong interactions, highlighting recent experimental and theoretical developments in meson and baryon sectors.

Contribution

It provides an overview of chiral perturbation theory applications, discusses new experimental results, and compares different renormalization schemes for nucleon form factors.

Findings

Electromagnetic polarizabilities of the pion have been experimentally extracted.

A consistent power counting scheme for the one-baryon sector is addressed.

Lorentz-invariant renormalization schemes are applied to nucleon electromagnetic form factors.

Abstract

Chiral perturbation theory is the effective field theory of the strong interactions at low energies. We will give a short introduction to chiral perturbation theory for mesons and will discuss, as an example, the electromagnetic polarizabilities of the pion. These have recently been extracted from an experiment on radiative $\pi^+$ photoproduction from the proton ($\gamma p\to \gamma \pi^+ n$) at the Mainz Microtron MAMI. Next we will turn to the one-baryon sector of chiral perturbation theory and will address the issue of a consistent power counting scheme. As examples of the heavy-baryon framework we will comment on the extraction of the axial radius from pion electroproduction and will discuss the generalized polarizabilities of the proton. Finally, we will discuss two recently proposed manifestly Lorentz-invariant renormalization schemes and illustrate their application in a calculation of the nucleon electromagnetic form factors.