Recent developments in the theory of large transverse momentum processes

One of the most important questions in hadron dynamics is the understanding of the underlying mechanisms for the production of large transverse momentum particles. The emerging features of the associated particles accompanying a high psub(UPSILON) trigger (jet structure, coplanarity, angular correlations, scaling laws) lend support to an underlying two-body hard scattering mechanism. Although it was natural to hope that the basic large psub(UPSILON) mechanism could be related to elementary quark-quark scattering, the new proton target data at FNAL appeared to rule this out. The evidence is reviewed for this, and a comparison is given with the predictions of the constituent interchange model (CIM) which postulates that the important subprocesses involve quark-hadron scattering