Study of the reactions vp. -->. mu. /sup -/. delta. /sup + +/ at high energies and comparisons with theory

We present production and decay distributions for the reaction vp ..-->.. ..mu../sup -/p..pi../sup +/ with M/sub ..pi../+/sub p/ .. ..mu../sup -/..delta../sup + +/, but we find evidence for the presence of non-..delta.. amplitudes for Q/sup 2/ > 1 GeV/sup 2/. The data are fitted by various theoretical models. For Q/sup 2/ < 1 GeV/sup 2/ the best fit yields the value M/sub A/ = 1.25/sup +0.15//sub -0.13/ GeV, using a dipole-nucleon axial-vector form factor in Alder's model, although none of these models successfully reproduces the observed ..delta..-decay distributions.