Scattering amplitudes beyond the planar limit of quantum chromodynamics

Thesis

Scattering amplitudes provide insight into the all-orders structure of gauge theories. Particularly rich is their non-planar sector, where new and interesting physical phenomena appear. This thesis aims to push the boundaries of perturbative scattering amplitudes, with special emphasis on calculations in massless Quantum Chromodynamics. We review the colour and helicity decomposition of gauge theory amplitudes, as well as the structure of their ultraviolet and infrared divergences. We then discuss the application of state-of-the-art methods to the computation of all four-point three-loop scattering amplitudes in Quantum Chromodynamics. As an immediate consequence we both verify the structure of infrared divergences and extract the gluon Regge trajectory at the corresponding perturbative order. We further describe the computation of five-gluon scattering at the two-loop order, with special emphasis on the multi-scale complexity of this process. Finally, we explore the idea of simplifying the integrand representation of gauge theoretic scattering amplitudes by leveraging their highly-constrained infrared structure. We provide a proof-of-concept application to two-loop four- gluon scattering amplitudes.

Authors: Gambuti, G

• DOI: 10.5287/ora-54ydbzjxp
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: high-energy physics; quantum field theory; scattering amplitudes; quantumchromodynamics; collider physics; mathematical physics; gauge theory; gluon; quark; qcd; particle physics
• Subjects: Quantum field theory; Quantum chromodynamics; Gauge fields (Physics); Scattering amplitude (Nuclear physics)