Polarization inπ−p→ηn, the Double-PoleA2, and a Possible Pion Conspirator

The ${\pi }^{-}p\to \eta n$ differential-cross-section data are analyzed within the Regge framework, using two $A_2$ trajectories which are constrained to reproduce the double-pole characteristics at $J=2\mathrm{}$, $t={\left(1.3\mathrm{} \mathrm{GeV}\right)}^2$ of the $A_2$ mass distribution. The best fit yields an upper trajectory degenerate with that for the $\rho$ and a lower-lying trajectory degenerate with that for the pion at $t=0\mathrm{}$ (a possible pion conspirator). The calculated neutron polarization is in reasonable agreement with new measurements, although these data were not employed in the fitting.