  An investigation of the s-wave channels in meson-meson scattering is
performed within a U(3) chiral unitary approach. Our calculations are based on
a chiral effective Lagrangian which includes the eta' as an explicit degree of
freedom and incorporates important features of the underlying QCD Lagrangian
such as the axial U(1) anomaly. We employ a coupled channel Bethe-Salpeter
equation to generate poles from composed states of two pseudoscalar mesons. Our
results are compared with experimental phase shifts up to 1.5 GeV and effects
of the eta' within this scheme are discussed.
