Meson Mass Splitting, CoplanarU(3)×U(3)Symmetry, and Nucleon-Nucleon Scattering

For the case of nucleon-nucleon scattering, it is shown that there are large corrections to the prediction of coplanar $U\left(3\right)\mathrm{}\times U\left(3\right)\mathrm{}$ symmetry as a consequence of the mass-splitting effects in the intermediate meson states of the crossed channels. These corrections are calculated for certain coefficients of the $\mathrm{pp}$ scattering amplitude by using a meson pole model. A comparison is given with the result of experimental phase-shift analyses.