We review some attempts to solve the Naturalness problem  namely the the lightness of the Higgs mass in relation to the scale of new physics  and the strong CP problem, that is the measured CPinvariance in the strong sector despite the presence of the socalled term. In particular, in the first part we study the socalled composite Higgs models as a solution to the Naturalness problem, focussing our attention on a particular model, the minimal linear sigma model. In the second part we review one of the most convincing explanation to the strong CP problem, the socalled axions. There are essentially three ways to introduce axions in a beyond Standard Model Lagrangian; after a short summary, we focus on the socalled KSVZ model and verify why it is safe from possible finetuning problems. Finally, we investigate the possibility to solve both the problems in an unique framework, the socalled axion minimal linear sigma model. These models, unlike the KSVZ model, suffers finetuning problems that suggest to associate the arising NambuGoldstone boson to a more massive axionlike particle, rather than an axion.
Composite Higgs and Axions: Towards a Natural Theory
Santagata, Michele
2018/2019
Abstract
We review some attempts to solve the Naturalness problem  namely the the lightness of the Higgs mass in relation to the scale of new physics  and the strong CP problem, that is the measured CPinvariance in the strong sector despite the presence of the socalled term. In particular, in the first part we study the socalled composite Higgs models as a solution to the Naturalness problem, focussing our attention on a particular model, the minimal linear sigma model. In the second part we review one of the most convincing explanation to the strong CP problem, the socalled axions. There are essentially three ways to introduce axions in a beyond Standard Model Lagrangian; after a short summary, we focus on the socalled KSVZ model and verify why it is safe from possible finetuning problems. Finally, we investigate the possibility to solve both the problems in an unique framework, the socalled axion minimal linear sigma model. These models, unlike the KSVZ model, suffers finetuning problems that suggest to associate the arising NambuGoldstone boson to a more massive axionlike particle, rather than an axion.File  Dimensione  Formato  

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https://hdl.handle.net/20.500.12608/28315