S-channel helicity conservation in elastic processes

The unitarity equation for elastic partial-wave amplitudes is considered. Defining helicity-total-flip elastic amplitudes as those in which both helicities change sign, it is observed that the unitarity equation strongly suggests that the imaginary part of the helicity-total-flip partial-wave amplitude is much smaller than that of the nonflip amplitude at high energies. Appealing to a plausibility argument, the ratio of helicity-total-flip to helicity-nonflip partial-wave amplitudes is estimated to be (1s)12 or smaller. The implications of this result for the full amplitude, the possibility of extending the result to other amplitudes if factorization is true, and the implications for Regge theory are discussed.