Vertex Functions and Bound States in Strongly Interacting Theories

Speaker: Milan Vujinovic, IFSC

When/Where: 4:30 PM, October 19, 2016 (Sala 210)

Abstract: Protons and neutrons, the particles which make up the nuclei of atoms, are comprised of tiny constituents called quarks. Quantum chromodynamics (QCD) is a field theory which describes the so-called strong “colour” force, mediated by gluons, which binds the quarks together and is responsible for formation of nucleons and other objects, collectively known as hadrons. While there is ample experimental evidence that this theory is correct, there are certain phenomena related to hadrons which are not yet fully understood within the QCD framework. We attempt to elucidate some of these issues by studying QCD and similar models by means of the Dyson-Schwinger and Bethe-Salpeter (DS/BS) functional formalism. This approach allows one to work with the basic degrees of freedom of QCD, the quarks and gluons (which are not directly detectable in experiments, being eternally bound within hadrons), while at the same time giving access to physical observables like hadron masses and decay constants. We briefly discuss the main ideas behind the DS/BS framework, and give examples of its applications through an investigation of one of the fundamental interaction vertices in QCD, as well as a calculation of light hadron masses in a model similar to chromodynamics. Our findings help in building towards a better understanding of not just QCD but strongly-interacting theories in general, which is important since some of these templates play an important role in other areas of high-energy particle physics.