On observable particles in theories with a Brout-Englert-Higgs effect.

Even at weak coupling the physical, observable spectrum of gauge theories with a Brout-Englert-Higgs effect can deviate from the elementary one of perturbation theory. This can be analytically described and treated using the Fr\"ohlich-Morchio-Strocchi mechanism. We confirm this by lattice simulation for an SU(3) gauge theory with a fundamental scalar, a toy model for grand unification. We also show that this has experimentally observable consequence, e.g., in scattering cross-sections of lepton collisions in this toy model.