Parton model and large P(_t) phenomena

Abstract

Our understanding of large P(_t) phenomena from the point of view of the quark-parton model is reviewed in this thesis. For this purpose some necessary experimental and theoretical background related to low P(_t) phenomena is given in the first chapter. We show in particular that the inclusive single particle cross section at low P(_t) follows a simple curve but that this falls far below the data when it is extrapolated to high P(_t). This suggests the existence of small constituents. In the second chapter we show how the existence and properties of these constituents are established in the simpler situation of lepton-hadron scattering processes. The constituents are approximately point-like, spin one-half, quarks. In the third chapter we see how large P(_t). hadronic processes can be used to probe the small scale structure of hadrons, and how the experimental results confirm the quark structure. We discuss several versions of the model and show that a reasonably consistent picture emerges. There are, however, some difficulties which can hopefully be overcome by the introduction of QCD (gluon) corrections. For this mixed experimental-theoretical review, kinematics concerning two-body and inclusive reactions are given in Appendices A and B. Also, related to the low P(_t) discussion of the first chapter, some theoretical background (e.g. scaling, limiting fragmentation and Regge-Muller formalism) is given in Appendix C.