Comparison of the differential cross-sections for. pi. /sup -/p. -->. eta'n and. pi. /sup -/p. -->. eta n at 8. 4 GeV/c. [Simple quark model, quadratic mixing]

Preliminary data are presented based on 45 percent of the sample, from a simultaneous study of ..pi../sup -/p ..-->.. eta'n, eta' ..-->.. eta..pi../sup +/..pi../sup -/, eta ..-->.. ..gamma gamma.., (1770 events) and ..pi../sup -/p ..-->.. etan..pi../sup 0/..pi../sup +/..pi../sup -/ ..-->.. ..gamma gamma.., (3250 events) at 8.4 GeV/c, covering a range of momentum transfer t' from 0 to 1.7 (GeV/c)/sup 2/. Both charged pions and both ..gamma..'s from each reaction were measured in the charged and neutral spectrometer at the Argonne ZGS. Backgrounds are 2 to 5 percent. The shapes of dsigma/dt for the two reactions are found significantly different, the eta' having considerably less forward turnover. The ratio of dsigma/dt at t' = 0 is (within present understanding of the systematics) consistent with a simple quark model and quadratic mixing angle approximately -10/sup 0/.