A Dipole Model for High Energy QCD

Detta är en avhandling från Department of Astronomy and Theoretical Physics, Lund University

Sammanfattning: This thesis considers a model of high energy particle collisions. The model is based on the so called BFKL formalism which is valid only at low x, that is collisions at very high energies, such as at the LHC. The intial state of the incoming particles are simulated by colour dipoles in transverse space evolved through rapidity. With this approach, all fluctuations are dynamically described, allowing for a large set of observables to be calculated. The first paper compares the model to experimental results and the model is found to describe a large set of experiments with $pp$ and $ga^'p$ accurately with just four tunable parameters. The second paper studies the fluctuations in the interaction probability, and how this affects the cross section for diffractive excitation in $pp$ and $ga^'p$. The model is further compared to a different approach, and many similarities are noted. The third paper studies the correlations between multiple hard subscatterings in $pp$ which are important for finding new physics at LHC. The fourth paper is the largest project, and introduces a full event generator based on the dipole model. Here the dipoles are not only tracked in the initial evolution, but also all the particles coming out from the collision are calculated. It is found to provide a competetive description of all minimum bias data, something that has never been done in the BFKL formalism before. This provies a good comparison for other event generators that normally use a different approach.

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