On modified Regge representations of the Khuri type

The unmodified Regge pole contribution to a scattering amplitude [see Eq. (I.1)] shows several undesirable features: As a function ofz it exhibits spurious singularities and for ReαKhuri has described a modified Regge representation which has much improved properties. Modifications of the same type are investigated in this paper in a more systematic way. It is shown that several classes of modified representations can be derived,Khuri's representation being contained in one of these. Some of these representations can be excluded, when a threshold behaviour like that of the physical amplitude or when a decreasing asymptotic behaviour for Reα