Univ Valencia, CSIC, Dept Fis Teor, E-46100 Valencia, Spain
; Univ Valencia, CSIC, IFIC, E-46100 Valencia, Spain
; Chinese Acad Sci, Inst High Energy Phys, Beijing 100039, Peoples R China
Article; Proceedings Paper
The s-wave isoscalar pi pi 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 pi pi properties in vacuum, in the scalar-isoscalar channel up to 1.2 GeV giving rise to poles in the T matrix for the f(o)(980) and the sigma. 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 pi N --> pi pi N reaction.