LOW-ENERGY PION-PION PARAMETERS FROM FORWARD DISPERSION RELATIONS

Values of the ππ scattering lengths and low-energy phase shifts are tabulated corresponding to various assumptions on the mass and width of the sigma meson. The method uses forward and first derivative dispersion relations. The I = 0 S-wave scattering length ao comes out in the range -0.3 to 0.6 mπ-1. The P-and D-wave scattering lengths are relatively independent of the sigma parameters. Solutions are compared with results on Ke4 decay and with the predictions of current algebra. Super broad sigmas seem to be preferred. Such solutions are also more self consistent in a bootstrap sense. © 1969.