Evidence for a low-lying unrenormalized vacuum trajectory fromNNscattering

Abstract

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