Title
Two aspects of strong interactions
Abstract
In Part I, I shall present some aspects of the production of heavy quarkonia in hadronic collisions. This is the direct continuation of my undergraduate dissertation . More precisely, I shall consider the uncertainties specific to the theoretical model used, i.e. the Color Singlet Model. I shall give an analysis of the influence of the uncertainties of the proton parton distribution functions on the differential cross-sections of hadronic heavy quarkonia production as well as the influence of the uncertainties on the wave function. The point of this study is to show -- even if this was commonly believed -- that theoretical errors are not sufficient to explain the discrepancies between Tevatron measurements and the predictions of the CSM as exposed in the Chapter 2 of my undergraduate dissertation . This study moreover allowed me to quantify the theoretical errors with a better precision. Still in Part I, I shall then expose my work on the introduction of a non-vanishing relative three-momentum between quarks constituting the heavy mesons. Another step in the improvement of the classical CSM which I shall mention is the introduction of a non-vanishing relative energy and of a relativistic wave function for the mesons. In the following, I shall talk about the non static extension of the CSM when refering to this improvement. Part II will be devoted to the study of pion and scalar structure functions. The study of these is part of a wider project related to off-diagonal hadron structure functions and is done in context of the ESOP European Network. The subjects of Part I and Part II, although a priori not linked, do not differ substantially. As it will appear, the structure of the calculations of quarkonia production and of our model for pion structure functions are somehow very similar. In a general point of view, the main differences come from the nature of the particules which induce different vertex functions and differences in kinematics.