Evidence for a low-lying unrenormalized vacuum trajectory from NN scattering

The apparently anomalous energy dependence of the pp and pn elastic polarizations at low energies are used to motivate the existence of a low-lying vacuum trajectory sigma with intercept α/sub sigma/ < 0 coupling more strongly to baryons than to mesons. The sigma is identified with the medium-range attractive NN force in one-boson-exchange models at lower energies. We conjecture that the sigma trajectory undergoes some nondiffractive renormalization at p/sub lab/ approximately-greater-than 30 GeV/c in analogy with recent models of the Pomeron. The possible presence of other low-lying trajectories is briefly discussed