Abstract
We construct an extension of the Standard Model (SM) which is based on grand unification with Pati-Salam symmetry. The setup is supplemented with the idea of spontaneous flavour symmetry breaking which is mediated through flavon fields with renormalizable couplings to new heavy fermions. While we argue that the new gauge bosons in this approach can be sufficiently heavy to be irrelevant at low energies, the fermionic partners of the SM quarks, in particular those for the third generation, can be relatively light and provide new sources of flavour violation. The size of the effects is constrained by the observed values of the SM Yukawa matrices, but in a way that is different from the standard minimal-flavour violation approach. We determine characteristic deviations from the SM that could eventually be observed in future precision measurements.
Highlights
Grand Unified Theories (GUTs) represent an attractive direction to search for extensions of the Standard Model (SM) of particle physics
We construct an extension of the Standard Model (SM) which is based on grand unification with Pati-Salam symmetry
The setup is supplemented with the idea of spontaneous flavour symmetry breaking which is mediated through flavon fields with renormalizable couplings to new heavy fermions
Summary
Grand Unified Theories (GUTs) represent an attractive direction to search for extensions of the Standard Model (SM) of particle physics (see e.g. [1]). Adopting a non-supersymmetric framework, we will focus on the PS gauge group with an explicit Z2 symmetry relating the couplings and representations of the two SU(2) group factors (which affect the left- and right-chiral SM fermions, respectively) Recent work in this framework [10,11,12,13,14,15,16,17] suggests that it is worthwhile to consider PS scenarios with an extended field content (as compared to minimal setups) where the breaking from the PS group to the SM group involves several distinct mass scales which eventually realize gaugecoupling unification at the GUT scale. Supplementary material and more technical details are provided in the appendix
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