Multi-Regge analysis of the exclusive and inclusive production of low-mass rho-pi systems

A Reggeized Deck model is constructed for the exclusive reaction π-p → rho0π-p that satisfies the Steinmann relation in the physical region. An explanation is given for the success of the Reggeization in this low-rho π-mass region. Resonancelike behavior is isolated in the rho-π-cut term, and a resonance-type loop is shown to be present in the 1+/s-wave Argand diagram. The multi-Regge expansion for the eight-particle amplitude with one triple-Regge and two double-Regge couplings, appropriate to the inclusive reaction π-p → rho0π-X, is also considered in detail. It is shown that, under trivial conditions and with a suitable choice of helicity contours, the double-Regge couplings in the multi-Regge (MR) limit are identical, to leading order, with couplings obtained in the mixed helicity-pole Regge-Pole (HPRP) limit appropriate to inclusive reactions. As a plausibility argument for the identity of the MR and HPRP limit, an intuitive picture of a way in which helicity poles may be visualized at the triple-Regge vertex is presented. For the assumption of the identity of the double-Regge couplings in the exclusive and inclusive cases, the problem of isolating this mechanism experimentally is discussed. Experimental tests for the identity of the couplings are proposed. The origin of the problems associated with observing the A1 meson in the exclusive reaction, and discuss mechanisms by which it might be seen in the inclusive case, are discussed