Predicting the Proton Mass fromππScattering Data

We relate experimental information on $\pi \pi$ scattering to tree-level effective chiral Lagrangians. The result is of a form similar to that used in Skyrme-type models of the proton, where the nucleons are described as topologically stable solitons of the chiral fields. In such models, one can express the proton mass in terms of measured scattering data, with the result $M_p=880\mathrm{}\pm 300$ MeV. We interpret this as a consistency test for the Skyrme models.