Examination ofρ0Density Matrix Elements Used for Vector-Dominance-Model Tests

We have studied the data on ${\rho }^0$ production in ${\pi }^{-}p$ interactions which have been used in tests of the vector-dominance model. We find inconsistencies between the assumptions made in the tests and the detailed characteristics of the data. In particular, the density matrix element ${\rho }_{1-1}$ for ${\rho }^0$-meson decay does not show the ${sin}^2\theta$ dependence expected ($\theta$ is the polar decay angle in the helicity frame), assuming only $s$- and $p$-wave $\pi \pi$ interactions. We conclude that the breakdown of the model has not been established by these tests.