Roy–Steiner-equation analysis of pion–nucleon scattering

¹ Helmholtz-Institut für Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universität Bonn, D–53115 Bonn, Germany
² Institut für Kernphysik, Institute for Advanced Simulation, and Jülich Center for Hadron Physics, Forschungszentrum Jülich, D–52425 Jülich, Germany
³ Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern, Sidlerstrasse 5, CH–3012 Bern, Switzerland
⁴ Institute for Nuclear Theory, University of Washington, Seattle, WA 98195-1550, USA

^a Speaker, e-mail: meissner@hiskp.uni-bonn.de
^b Speaker, e-mail: elvira@itp.unibe.ch

Published online: 22 March 2017

Abstract

Low-energy pion–nucleon scattering is relevant for many areas in nuclear and hadronic physics, ranging from the scalar couplings of the nucleon to the long-range part of two-pion-exchange potentials and three-nucleon forces in Chiral Effective Field Theory. In this talk, we show how the fruitful combination of dispersion-theoretical methods, in particular in the form of Roy–Steiner equations, with modern high-precision data on hadronic atoms allows one to determine the pion–nucleon scattering amplitudes at low energies with unprecedented accuracy. Special attention will be paid to the extraction of the pion–nucleon σ-term, and we discuss in detail the current tension with recent lattice results, as well as the determination of the low-energy constants of chiral perturbation theory.^c