The purpose of this paper is to draw attention to the importance of the backward reaction ${\pi }^{+}p\to p{\rho }^{+}$ as a test of the wrong-signature nonsense Regge dip mechanism. If the observed dip in backward ${\pi }^{+}p\to p{\pi }^{+}$ is due to a wrong-signature nonsense zero, then a dip is also predicted to occur in ${\pi }^{+}p\to p{\rho }^{+}$. This prediction does not involve any arbitrary assumptions about fixed poles, exchange degeneracies, or absorptive Regge cuts.

• Received 20 May 1971

DOI:https://doi.org/10.1103/PhysRevD.5.198