Two pion decay of the Roper resonance

We evaluate the two-pion decay of the Roper resonance in a model where explicit rescattering of the two final pions is accounted for by the use of unitarized chiral perturbation theory. Our model does not include an explicit ε or σ scalar-isoscalar meson decay mode; instead it generates it dynamically by means of the pion rescattering. The two ways, explicit or dynamically generated, of introducing this decay channel have very different amplitudes. Nevertheless, through interference with the other terms of the model, we are able to reproduce the same phenomenology as models with explicit consideration of the ε meson.