Theory of Hadronic Atoms

A review of the modern theory of hadronic atoms based on the non-relativistic effective Lagrangian approach and ChPT, is given. As an application of the general framework, we consider the decay of the ππ atom into two neutral pions, and the energy-level shift of the π−p atom. The analysis of the decay width of the ππ atom has been carried out at the first non-leading order in isospin breaking, and at O(ep) in ChPT, that results in an accurate theoretical prediction for this quantity. The study of the π−p atom energy-level shift within the same approach clearly demonstrates the necessity to critically reaccess the values of the πN scattering lengths, extracted from the energy-level shift measurement by means of the potential model-based theoretical analysis. The construction of short-range hadronic potentials from field theory is also discussed.