2024/06/26 by Mario Fernández Navarro, Navarro, Mario Fernández
Computer Science · Physics and Astronomy · #Computational Physics and Python Applications #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #High Energy Physics - Theory (hep-th)
paper · pdf · doi:10.48550/arxiv.2406.18411
openalex publication_date 2024/06/26 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The flavour puzzle remains as one of the most intriguing enigmas of particle physics. In this thesis, we propose and study theories of flavour which generically hint to a multi-scale origin of flavour. First we explore the idea of fermiophobic models and messenger dominance, where the chiral fermions of the Standard Model are uncharged under (part of) an extended gauge symmetry, which also forbids Yukawa couplings for chiral fermions. These are generated effectively due to the presence of hierarchically heavy messengers, including vector-like fermions and/or heavy Higgs doublets. Simultaneously, this mechanism generates effective couplings of chiral fermions to the gauge bosons of the extended symmetry, leading to a predictive phenomenology connected to the origin of flavour hierarchies. We present two models of this kind, based on gauge U(1) and twin Pati-Salam symmetries, that have implications for low energy flavour anomalies. Secondly, we study the framework of flavour deconstruction, where the Standard Model emerges from a non-universal gauge theory that contains a separate gauge factor for each fermion family. We argue that one of the most simple ways to achieve this is by assigning a separate gauge hypercharge to each fermion family, denoted as the "tri-hypercharge" theory. If the SM Higgs only carries third family hypercharge, then only the third family is massive at renormalisable level, and light families get their mass from higher dimensional operators. Finally, we propose a gauge unified origin for gauge non-universal frameworks such as the aforementioned tri-hypercharge theory. The model assigns a separate SU(5) group to each fermion family. However, assuming that the three SU(5) groups are related by a cyclic permutation symmetry ℤ3, then the model is described by a single gauge coupling in the ultraviolet, despite SU(5)3 being a non-simple group.