On Reggeized Absorption in the Presence of the Shielded Fixed-Pole Pomeron

Abstract

By the use of the double-partial-wave formal,ism, the structure of absorptive Regge sin­ gularities is examined in the case of the fixed simple pole Pomeron with Arnold and Barnett's shielding-cut mechanism. It is shown that the full partial wave amplitude contains a moving branch cut of (inverse-) square-root type in relation to the mr-(KK-)shielding branch cut, in addition to a fixed branch cut of logarithmic type, that the physical partial wave amplitude has the pafticle pole with the increased residue and that the asymptotic behaviour of the full Reggeonic amplitude is controlled by the input Regge pole at least in the neighbour­ hood of t=O. Phenomenological features of the recent CERN-ISR data on p-p collision seem to suggest that the Pomerania (but not the asymptopia) has approximately been attained at high energies available at the CERN-ISR, and that the possibility of an isolated, factorizable Pomeron at l= 1 should be discarded at the CERN-ISR energies. 1> Of what kind is the Pomeron which is compatible with these observations? As an example, there is a phenomenological model of the fixed simple pole Pomeron (FSPP) with Arnold and Barnett's shielding-cut (ABSC) mechanism. 2>,s> In such a scheme, of course, the increasing trend of cross section is interpretable as a transient phenomenon at non-asymptotically high energies and the totally energy-independent behaviour of diffraction scattering is predicted to appear at the asymptopia. Since asymptotically divergent cross section has not yet been established by the presently available data, it will be of physical significance to examine theoretical consequences of Reggeized absorption in the case of FSPP with ABSC mechanism. In this note, the double-partial-wave (DPW) procedure 4>'5> is applied to studying the structure of leading absorptive Regge singularities in the presence of ABSC mechanism. For the sake of brevity, our discussion is mainly confined to FSPP having just ABSC fie (t) = 1- m,.2 + t/4, which shields the nn threshold in the t channel as l tends to 1. First of all, the single-Reggeon-exchange amplit~de MR (s, t) is assumed to be parametrized by*>