Evidence forN*Regge Trajectory Clans with Approximate Parity Degeneracy

Resonances recently discovered in $\pi N$ phase-shift analyses are assigned to linear Regge trajectories. The proposed classification is interpreted as evidence for (i) secondary trajectories displaced down from the leading trajectories by ${\alpha }_S\simeq {\alpha }_L-n$ ($n$ an integer) and (ii) approximate degeneracy of trajectories with opposite parity, the same signature, and equal isospin (i.e., MacDowell symmetric).