I will talk about a generalization of effctive range expansion with a left-hand cut due to the t- or u-channel exchange of a particle with a small finit mass. The generalization is constructed using the N/D method of dispersion theory and has a Pade-like form. The applicability will be shown by extracting the NNpi coupling from NN scattering phase shifts using this formalism.
Many excited mesons decay to three hadrons. Some of them are not even resonances but kinematic enhancements from three particles being on-shell in a triangle configuration. Other systems are dynamically generated from three-body interactions leading to resonance poles. Examples for these phenomena from phenomenology and lattice QCD is presented involving the $K(1460)$, $\pi(1300)$,...
Determination of the Roper resonance with two- and three-body unitarity
We study the effect of a finite volume for pion-pion scattering over energy levels and physical observables such as the phase-shift or pion mass. The method to determine the energy levels is done using a finite set of Crystal harmonics or the matrices which represents the Irreps properly, which expands our Inverse Amplitude Method, over a set of irreducible groups of rotations from the...
