UV Completion of Composite Higgs Models

Overview & Synopsis

The Standard Model (SM) is the most successful theory describing the particle interactions. Its predictions, incredibly precise, agree very well with the experimental data. The last proof being the discovery of the Higgs boson in 2012, which is at the origin of the mass of the other particles, thus essential to the theory. However, the SM cannot explain everything: - Experiments have confirmed a mass for the neutrinos, which the SM does not provide. -The gravitational interactions are not a part of the SM. -The dark matter, hypothetical particle to explain the astrophysics observations, is not taken into account in the SM - The Higgs Mechanism that generates a mass to the boson is ad-hoc via the introduction of the Higgs potential. The Higgs mass also suffers from the quadratic divergences of new physics. Those reasons push us to believe that the SM is just the low energy manifestation of a more fundamental theoy. The main subject of the thesis are the Composite Higgs Models, which principaly try to solve the last issue of the above list. In this class of models, the higgs Boson, and all its ineractions, are replace by a new fermionic sector very similar to Quantum ChromoDynamic (QCD). For that purpose, new fermions called technifermions are introduced and charged under a new color dubbed technicolor. Like the color in QCD, the technicolor theory confines at low energy and a condensate breaks its global symmetries. This generates Goldstone bosons which can play the role of the SM Higgs boson. By its bound state nature, the new Higgs boson has no more issues with the quantum correction of its mass. In this scenario the new strong interaction gives a dynamical origin to the Higgs potential. Nontheless, challenges appear if we want to generate a mass for the SM fermions. The paradigm of Partial Compositness try to overcome this issue and postulate a linear mixing between the SM fermions and technibaryons, fermionic bound state of three technifermions, like the quarks forming the proton.