In this work, the reaction γp→ ρ fast 0 p π+π – has been studied with the linearly polarized 20-GeV monochromatic photon beam at the SLAC Hybrid Facility to test the prediction of s-channel helicity ...conservation in inelastic diffraction for t ’ <0.4 (GeV/c )2 . In a sample of 1934 events from this reaction, the ρ0 decay-angular distributions and spin-density-matrix elements are consistent with s-channel helicity conservation, the π+ π – mass shape displays the same skewing as seen in the reaction γp→p π+ π – , and the p π+ π – mass distribution compares well and scales according to the vector dominance model with that produced in π± p→ π fast ± p π+π – .
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