Gauge invariant spectra and FMS mechanism for gauge theories with BEH effect

by Mr Vincenzo Afferrante (University of Graz)

Thursday 8 Oct 2020, 14:00 → 15:00 Europe/Berlin

Hörsaal 3 (Helmholtzweg 3)

A correct nonperturbative treatment of gauge theories requires physical particles to be described by gauge invariant operators. It is then appropriate to use composite operators made of elementary gauge dependant fields as physical observables. The standard model presented nonetheless astonishing phenomenological predictions with perturbation theory on gauge fixed elementary fields. FMS mechanism shows in an elegant way why this is the case, and also that for other gauge theories the usual perturbative procedure can lead to potential deviations from the physical spectrum.

A basic introduction to the FMS mechanism and some examples of its applications are discussed. In the most recent, it is explored the case of Wilson SU(2) vector-like fermions coupled with a scalar in the fundamental representation with a Yukawa term. Our goal is to show, as a proof of principle, that the mass of a Higgs-fermion bound state is the same as the elementary fermion mass calculated in a fixed gauge. This result can be a hint that left-handed leptons in the SM are such bound states. Preliminary results with quenched fermions seem to corroborate the hypothesis.