A duality-inspired model for the scattering amplitude is used to explain backward ${\pi }^{+}p$ elastic-scattering data from $2.18 \frac{\mathrm{GeV}}{c}$ (incident pion laboratory momentum) on up. The quantitative success of this model gives support to the assumption that the dip at $u\sim -0.15\mathrm{}$ Ge${\mathrm{V}}^2$ is due to a wrong-signature nonsense zero in the $N_{\alpha }$ Regge-pole exchange amplitude. A particularly interesting polarization prediction (which can soon be compared with experimental data) is also presented.

• Received 17 August 1970

DOI:https://doi.org/10.1103/PhysRevD.3.1264