Phenomenological study on classically scale invariant models towards natural realization of the Higgs mass

Abstract

Although the standard model (SM) can explain almost all experimental results obtained until now, there are unsolvable problems with the SM: active neutrino masses, baryon asymmetry of the Universe, dark matter relic abundance, dark energy, and so on. This fact clearly suggests existence of the beyond the SM. It is, however, well known that the hierarchy problem arises if new particles exist in a high energy scale compared to the electroweak scale. As an idea avoid- ing the hierarchy problem, classically scale invariant extensions have recently drawn a lot of attention. The classical scale invariance should be broken by some quantum effects, and there are roughly two breaking mechanisms: one is the Coleman-Weinberg mechanism, which is based on perturbation theory; another is the strong-coupling dynamics like the QCD, which is based on non-perturbation theory. In this thesis, we investigate these two types of models, and show the phenomenological consequences. In addition, we propose a new dynamics of the electroweak symmetry breaking in a classically scale invariant model, i.e., bosonic seesaw mechanism, and nd that a dark matter candidate naturally exits in the model.