Discussion of “Coupled Channel Methods at High Q 2 ”

1. Discussion of “Coupled Channel Methods at High Q2”

2. Franz Gross

11. T. Sato, H. Kamano

12. Some remarks • Definition of resonance parameters with poles and residues. • Breit-Wigner mass and width • Proper definition based on scattering theory. • Consistent with resonance theory based on Gamow vectors • (eigenvalue problem of full Hamiltonian with purely outgoing b.c.). • One of the main subjects also in nuclear physics (complex scaling method, …). • Closely related to the developments of NON-Hermitianquantum mechanics. • (See, e.g., “Non-Hermitian Quantum Mechanics”, N. Moiseyev, • Cambridge University Press, 2011) • Highly model-dependent quantities • Can be a good approximationof resonance pole mass if and only if: •  the pole is isolated from any other singularities in complex-E plane •  small background contributions ## Not a small number of light-flavor hadrons do not satisfy this condition: for example, Roper, f0(980), … ## One may analyze the data of real E with the BW parameterization, but there is no guarantee that the resulting BW mass and width describe the true resonance parameters.

13. SiggiKrewald

15. Victor Mokeev