The parity of regge cuts

The exchange of two reggeons of naturalities η_a and η_b will in general produce a J plane cut in amplitudes of both naturalities ± η_aη_b. We show that the amplitudes of naturality ? η_aη_b are suppressed, and this suppression grows with the energy, regardless of the particular model used for the vertices coupling the reggeons to the external particles. In consequence, for cuts where the two reggeons are any of ?, A₂, f, ω, or the pomeron, the natural-parity cut (if it is present) will dominate over the unnatural parity. We also show that cut vertices which contribute to both naturalities satisfy the conspiracy condition at t = 0 by suppressing both contributions equally. Away from t = 0, the η = + η_aη_b contribution can recover from this suppression. This behaviour is of importance in, for example, the pion-pomeron cut.We compare these conclusions with experiment.