  We enforce chiral Ward identities on the vertices of the linear sigma model
to take into account the width of the scalar sigma, considered as a true
physical resonance. We consider pion scattering at very low energies and, from
a fit to the measured phase shifts in the various angular momentum and isospin
channels, conclude a mass for the sigma of 600+200-100 MeV. Its width turns out
to be of the same size.
