Elastic scattering of a spin zero and a spin [formula omitted] particle at u = 0

Abstract

We examine the elastic scattering of a scalar particle (a pion) off a spin 1 2 particle (a nucleon) at u = 0 in a model of continuous-spin (E 2 representation) pole exchange and compare the results with the usual Regge-pole models. An interesting result is that continuous-spin pole exchange at u = 0 gives an asymptotic polarization which, depending on the magnitude of the exchanged spin, is different than zero in contrast to the vanishing polarization expected in any single Regge-pole exchange model or when we exchange a u-channel twin-Fermion Regge-pole pair that satisfies Mac-Dowel's reflection symmetry. Indeed measurement of this polarization tells us about the value of the second Casimir operator κ 0 characteristic of the mass-zero representation under exchange. The asymptotic unpolarized cross section then gives us the residue function.