Relevance of nucleon spin in an amplitude analysis of reactions pi(-)p->pi(0)pi(0)n and pi(-)p->eta eta n

The measurements of reactions pi(-)p-->pi(-)pi(+)n and pi(+)n-->pi(+)pi(-)p on polarized targets at CERN found a strong dependence of pion production amplitudes on nucleon spin. Analyses of recent measurements of the pi(-)p-->pi(0) pi(0)n reaction on unpolarized targets by the GAMS Collaboration at 38 GeV/c and the BNL E852 Collaboration at 18 GeV/c use the assumption that pion production amplitudes do not depend on nucleon spin, in conflict with the CERN results on polarized targets. We show that measurements of pi(-)p-->pi(0) pi(0)n and pi(-)p-->eta eta n on unpolarized targets can be analyzed in a model-independent way in terms of four partial-wave intensities and three independent interference phases in the mass region where S and D waves dominate. We also describe model-independent amplitude analysis of the pi(-)p-->pi(0) pi(0)n reaction measured on a polarized target, both in the absence and in the presence of G-wave amplitudes. We suggest that high statistics measurements of reactions pi(-)p-->pi(0) pi(0)n and pi(-)p-->eta eta n be made on polarized targets at Protvino IHEP and at BNL, and that model-independent amplitude analyses of this polarized data be performed to advance hadron spectroscopy on the level of spin-dependent production amplitudes.