Toward a general description of two-body hadron reactions
Nuclear Physics B
We present a model for describing two-body high-cncrgy hadron reactions at energies above the resonance region. Although no real theory yet exists, we can give a procedure for obtaining a (possibly correct) description of the amplitudes for any two-body reaction (whatever the spins involved, including re',d and imaginary parts of amplitudes, any helicity-flip n-exchange as well as vector and tensor exchanges, etc.). The most important new physical effect inw~lved is using the appropriate
... appropriate t-dependent phase for the vacuum exchange amplitude (the pomeron), both in elastic scattering and in describing absorption effects. The pomeron is not a Regge pole. The model is very simple to formulate and has a reasonable physical interpretation in terms of important unitarity effects and absorption. It allows us to understand the partial successes and the inadequacies of previous approaches such as the dual absorptive model, the strong absorption model, the view that some amplitudes have Regge-pole behavior while others do not, etc. In the present paper we analyze "all the 0-½ + ~ 0-½ + reactions, np ~ pn, and iS p ---, nn, cross sections, polarizations and amplitudes; these include all the important kinds of helicity amplitudes for any two-body reactions. Apart from a few places the results are very good; we argue that the few places where there may be some difficulty arc duc to effects we have left out rather than to the structure of the model. Although the input reggeon exchanges are not ", 111 exchange degenerate, the phases of the output amplitudes after absorption show a remarkable and unexpected resemblance to what one would expect from exchange degenerate poles, apart from the necessity of having a zero structure related to important absorption corrections. A number of related results, some of which are considered puzzles, are discussed (total cross-section differences for nN and KN, the Increase m oT(K p), crossovers, shrinkage, real parts of elastic amplitudes, polarization single and double zeros, line reversed reactions, pp scattering at the ISR, etc.) and some predictions are given.