UNC-CH Physics and Astronomy Colloquium

Craig D. Roberts, Argonne National Laboratory

“Emergence of Mass in the Standard Model”

Quantum Chromodynamics (QCD), the nuclear physics part of the Standard Model, is the first theory to demand that science fully resolve the conflicts generated by joining relativity and quantum mechanics. Hence in attempting to match QCD with Nature, it is necessary to confront the innumerable complexities of strong, nonlinear dynamics in relativistic quantum field theory. The peculiarities of QCD ensure that it is also the only known fundamental theory with the capacity to sustain massless elementary degrees-of-freedom, gluons (gauge bosons) and quarks (matter fields); and yet gluons and quarks are predicted to acquire mass dynamically so that the only massless systems in QCD are its composite Nambu-Goldstone bosons. All other everyday bound states possess nuclear-size masses, far in excess of anything that can directly be tied to the Higgs boson. These points highlight the most important unsolved questions within the Standard Model, namely: what is the source of the mass for the vast bulk of visible matter in the Universe and how is this mass distributed within hadrons? This presentation will provide a contemporary sketch of the strong-QCD landscape and insights that may help in answering these questions.