The s-wave isoscalar π π scattering amplitude in a nuclear medium has been evaluated using a non-perturbative unitary coupled channels method and the standard chiral Lagrangians. The method is successful describing the π π properties in vacuum, in the scalar-isoscalar channel up to 1.2 GeV giving rise to poles in the T matrix for the ƒ0(980) and the σ. The extension of the method to the nuclear medium implies the renormalization of the pions in the medium and also the introduction of interaction terms related to contact terms in the πN → ππN reaction.Vicente Vacas, Manuel Jose, [email protected]
; Oset Baguena , Eulogio, [email protected]
