2018/04/12 by Axel Maas, Pascal Törek · 1 voice
Physics and Astronomy · #hep-lat #hep-ph
paper · pdf · doi:10.1016/j.aop.2018.08.018
published as Annals of Physics 397, 303 (2018) · 24 pages, 14 figures, 8 tables, font errors fixed
arxiv published 2018/04/12 · arxiv created 2018/04/16 · arxiv updated 2018/09/11
In gauge theories, the physical, experimentally observable spectrum consists only of gauge-invariant states. This spectrum can be different from the elementary spectrum even at weak coupling and in the presence of the Brout-Englert-Higgs effect. We demonstrate this for an SU(3) gauge theory with a single fundamental Higgs, a toy theory for grand-unified theories. The manifestly gauge-invariant approach of lattice gauge theory is used to determine the spectrum in four different channels. It is found to be qualitatively different from the elementary one, and especially from the one predicted by standard perturbation theory. The result can be understood in terms of the Froehlich-Morchio-Strocchi mechanism. In fact, we find that analytic methods based on this mechanism, a gauge-invariant extension of perturbation theory, correctly determines the spectrum, and gives already at leading order a reasonably good quantitative description. Together with previous results this supports that this approach is the analytic method of choice for theories with a Brout-Englert-Higgs effect.