Evaluation of the derivative quartic terms of the meson chiral Lagrangian from forward dispersion relations

Using the forward dispersion relations for scattering, we show that the coefficients of the derivative quartic terms in the chiral Lagrangian are positive. The Skyrme term is mainly given by the -meson contribution to the I=1 total cross section and gives a proton mass of 1. 27 GeV. The non-Skyrme term is found of comparable strength from the I=0 S-wave data.