Inelastic diffraction and factorization properties in the direct and crossed channels

Abstract

We introduce a simple phenomenological framework based on approximate factorization properties in the direct and crossed channels of diffractive processes. Observed gross features of diffraction then become related to gross features of diffractive states. From the observed slope-mass correlation it emerges through this framework that crossed-channel factorization is broken; increasingly massive diffractive states become increasingly transparent, and strong absorption for these states progressively weakens.The outstanding experimental features of inelastic diffractive processes appear to be the weak energy dependence, the slope-mass correlation, and factorizati~n.'*~ Details emerging from recent experiments have refined these features considerably and have added new ones such a s helicity dependence, detailed mass distributions, diffraction dips at low mass, slopes at high mass, and better estimates of total diffractive cross sect i o n~.~-'Theoretical attempts to describe the data include absorbed Regge-Deck,g Regge-Mueller inclusive models,1° quark-gluon,ll eikonal,12 and other model^.'^ Generally such models do well on the gross features and some details. On any particular process, especially exclusive processes, the state of phenomenological art i s such that one or more of the models is always able to accomodate most features of the data. They all have something more-or-less fundamental to say about the reaction mechanism.However, one is left with the unsettling feeling that, after all, we do not understand very much about why diffractive processes behave the way they do, perhaps because we a r e lacking a precise picture of the diffractive states themselves. We would like at least to know something more about the average nature of diffractive states which can be reached through the dissociation process.On the crudest level one might guess the p* is something like the p , but is it really bigger at low mass and smaller at high mass a s the slopemass correlation would seem naively to imply? What i s its transparency? What is its cross section for scattering on a proton? Some understanding of these things is clearly desirable, since some a r e almost m e a~u r a b l e . '~* '~ Ultimately, there is a range of dynarnical problems which involve diffraction indirectly, such as the strength of strong absorption and the nature of the Pomeron singularity, which bear on theor i e s such a s Reggeon field theories,'= dual Pomeron theories ,I7 and quantum-chromodynamic (QCD) theories." Of course, it may well be the other way around, that these theories will ultimately tell us everything about diffraction.In this paper we introduce a simple phenomenological framework based on some assumptions about the approximate factorization properties in the direct and crossed channels of diffractive processes. The advantage of doing this is that observed features of diffraction become related to gross features of diffractive states. Some unexpectedly good results follow from the observed slope-mass correlation, namely, that massive s...