Helicity-Amplitude Relations for Vector-Meson Production from a Skyrmion Model

Mattis has derived six relations among the partial-wave amplitudes for the reaction $\pi N\to \rho N$. From these relations we deduce that the six independent helicity amplitudes for the $t$-channel isospin-0 reaction may be simply expressed in terms of one unknown function. This leads to definite predictions for the $\rho$-meson density matrix and the absence of nucleon polarization effects, which can be tested directly, without recourse to partial-wave analysis.