Analyses of Electron-Proton and Hadron-Hadron Collisions Using the Linked Dipole Chain Model

Abstract: In this thesis we perform phenomenological studies of Quantum Chromodynamics, as manifested in deeply inelastic electron-proton (DIS) and high-energy hadron-hadron interactions. Most of the results are obtained using the Linked Dipole Chain model (LDC). This model was originally developed for studies of DIS and is formulated in terms of kT-factorization and un-integrated parton distribution functions. We develop a simple model, based on the CCFM and LDC models, which interpolates between the DGLAP and BFKL regimes in DIS. This model gives an intuitive qualitative picture of the transition region between the DGLAP and BFKL domains. We use an approximate version of the LDC model to obtain qualitative results for the inclusive minijet cross section and transverse energy flow, expected to be relevant in analyses of future high-energy hadron-hadron or nucleus-nucleus collisions. Our results contain a dynamical suppression at small transverse momenta, which corresponds to an effective cutoff which is slowly increasing with the total collision energy. This is in contrast to the traditional approach based on collinear factorization, which results in an inclusive cross section that diverges at small transverse momenta and implies the introduction of a cutoff parameter whose value needs to be adjusted to data. The LDC model is particularly suitable for a description of e.g. the cross section for jets and heavy quarks at very high energies, where the effects of finite transverse momenta of partons inside the hadrons become increasingly important. We obtain results for the LDC integrated and un-integrated gluon distribution functions and compare them with those of other formalisms, e.g. those based on the CCFM model, demonstrating how to make a relevant comparison between the different formalisms. We exploit the symmetric formulation of the LDC model with respect to the photon and proton ends and develop a version of the LDC model for hadronic interactions. In this preliminary analysis, we focus on features of jet and minijet production which are less sensitive to hadronization effects and compare our results to those of the PYTHIA event generator.