Who: Helene Gertov (CP3-Origins)
When: Monday, May 4, 2015
In this master thesis a perturbative and elementary extension of the Standard Model is presented. The Standard Model is extended to a SU(4) symmetry which breaks spontaneously to Sp(4) with five pseudo Goldstone Bosons. Three of them are to become the longitudinal components of the electroweak gauge bosons, one is to become an elementary pseudo Goldstone Boson Higgs and the last one is to become a pseudo Goldstone Boson Dark Matter candidate, since it is stable and neutral with respect to the Standard Model.
The Goldstone Bosons acquire a mass through the quantum corrections due to the Yukawa, and the electroweak gauge interactions does not preserve the full SU(4) symmetry. Since the theory is elementary and perturbative, the quantum corrections can be calculated by using the Coleman-Weinberg potential. When the one-loop corrections are taken into account, a mixing between the and one of the Goldstone Bosons will occur. Thus a superposition of these two fields is identified with the observed Higgs boson. The one-loop corrections from the top dominates and the vacuum is aligned in the direction, where the observed Higgs Boson is mostly a pseudo Goldstone Boson.
Comparing this model to the Large Hadron Collider experiments one finds, that the model is phenomenologically viable. Furthermore the Dark Matter particle leads to the observed thermal relic density, while respecting the most stringent current experimental constraints when the mass of the Dark Matter candidate is larger or equal to the mass of the observed Higgs boson.