An Eikonal model for multiparticle production in hadron-hadron scattering

The purpose of this thesis is the introduction of a model for multiparticle production in hadron-hadron interactions. An introduction to the broad issue of perturbative Quantum Chromodynamics (QCD) is presented in the first chapter with special emphasis on the concepts of renormalization, asymptotic freedom and scaling violation. In addition non-perturbative concepts such as Regge theory and Regge pole parametrisation of the total cross section are mentioned. The second chapter is a broad introduction to the Monte Carlo techniques used in event generators and numerical integrators with special emphasis on the methods used in the HERWIG event generator. The third chapter contains a brief overview of the main physics and methods used in HERWIG for simulation of large momentum transfer collisions between two hadrons. In Chapter 4 we introduce the physics of the underlying event and adopt a simple jet definition used by the CDF collaboration in the analysis of charged particle component of jets simulated by HERWIG in three different topological regions. For hard scattering proton-antiproton collisions we simulate the underlying event activity in each region using HERWIG's Underlying Event model and compare it to the experimental data. We thus independently confirm results obtained by the CDF collaboration. In Chapter 5 we present the Multiparton Interaction model used as a substitute to the HERWIG Soft Underlying event model. We examine whether the addition of secondary hard scatters to the main hard interaction improves the simulated data on the underlying event. We propose to tune the value of the proton radius used in the Hard Multiparton Interaction model in order to obtain a good agreement with the experimental data. In Chapter 6 we introduce a new Eikonal Monte Carlo model in order to simulate multiparticle production in hadron-hadron interactions. The model contains a single phenomenological input the total cross section for pp and pp scattering. We show a broad agreement between our model predictions and experimental data. We discuss its main advantages over the two underlying event models used in chapters 4 and 5. Finally we use the new Eikonal model to predict the underlying event activity which should be expected at the LHC.