Browsing by Subject "cross-section"

Quantum Chromodynamics (QCD) is the quantum field theory of strong interaction and therefore describes one of the fundamental forces in the universe. Quarks and gluons, together called partons, interact via strong force, and their interactions can be observed in high-energy collisions involving hadrons. Hadrons always contain some composition of quarks. The simplest way to obtain a partonic outgoing state in a collision, is through an electron-positron annihilation that produces a photon, which scatters, forming a combination of partons. Partons, unlike leptons, have properties known as color and flavor. There are six different types of quarks, all of which can be produced in a collision at sufficiently high energies. The energy involved in a hard collision of an electron and a positron is carried through the entire process. Generally, the partons’ binding to each other, known as color confinement, is so strong that they are observed as hadrons. Hadrons are color-neutral, meaning that the colored quarks are arranged such that they result in a color-neutral particle. This thesis focuses on calculating partonic collision outcomes on a small scale using perturbative QCD. At high energies and short distances, quarks are weakly coupled, allowing them to be considered relatively free from parton-parton interactions. By comparing the outcomes of electron-positron collisions, namely the electromagnetic and strong force (leptonic and partonic) outcomes, we can receive information on their differences when interacting. By constructing the process of leptonic annihilation, we can observe probabilities of charged particle outcomes that scatter from a photon. Furthermore, we calculate the cross-sections of the processes resulting in several partonic configurations. One of the results of this thesis is the ratio between the hadronic and leptonic outcomes stemming from the same initial collision. With partonic outcome cross-section calculated up to next-to-leading order, the ratio exhibits the impact of color factors as well as the running coupling of the parton-parton interaction.