Speaker
Bastian Kubis
(Bonn University)
Summary
We review the recent numerical solution of the Roy-Steiner equations for pion-nucleon scattering. One of the central results of this solution is a precise determination of the pion-nucleon σ term, based on a new, improved version of the Cheng-Dashen low-energy theorem that includes isospin-breaking corrections. In particular, we highlight the central role of the pion-nucleon scattering lengths for this determination, which are obtained experimentally from pionic-atom spectroscopy, and discuss possible ways to resolve the apparent tensions with lattice determinations of the σ term.
