In these lectures the concepts of S-matrix theory and their implications for a theoretically sound description of resonances are discussed. In particular I will explain the connection between causality and analyticity, the implications of unitarity for production reactions and scattering amplitudes and the concept of positivity. Finally I will explain under which conditions certain simplified descriptions are justified for individual resonances.

Biography

Christoph Hanhart is the recipient of the PIFI Distinguished Scientist Award (2025). He studied physics in Bonn and Sydney. As a theoretical physicist he works on phenomena of the strong interaction at the boundary between nuclear and particle physics at the Jülich Research Centre and at the University of Bonn, where he also holds an extraordinary professorship. The current focus is on investigations of exotic hadron states. He is a member of the Particle Data Group (PDG) and received the Teaching Award of the University of Bonn in 2018.

Inviter

Feng-Kun Guo