Hadronic atoms

TL;DR

This paper reviews the theory of hadronic atoms, emphasizing their role in studying low-energy hadron interactions, and introduces a systematic approach using non-relativistic effective Lagrangians to analyze their properties.

Contribution

It provides a systematic expansion method for hadronic atom observables using non-relativistic effective Lagrangians, including a pedagogical overview of the theoretical framework.

Findings

Systematic expansion of energy levels and decay widths in terms of the fine-structure constant.

Introduction of non-relativistic effective Lagrangian framework for hadronic atoms.

Educational review of key concepts like scale separation and power counting.

Abstract

We give a brief survey of the theory of hadronic atoms, which represent important sources of information for studying hadron interactions at very low energy. It will be namely demonstrated that a systematic expansion of the observables of hadronic atoms (the energy levels and the decay width) in terms of the fine-structure constant can be obtained, using the framework of non-relativistic effective Lagrangians. We also present a pedagogical introduction to the non-relativistic effective theories that includes a review of the main concepts, such as the scale separation, construction of the Lagrangian, power counting and matching.