Topic 3: A natural extension of the Standard Model
Description & objectives:
There are multiple theoretical and astrophysical reasons to expect new physics beyond the Standard Model (SM) of elementary particles. However, so far we
have no experimental indication for such new physics, therefore, theoretical investigations will have to follow general guiding principles such as
the amount of symmetry (the higher the better) and naturalness (the less fine-tuning the better) to find a viable beyond the SM theory. It is
straightforward to write down theories beyond the SM, but it turns out to be very hard to find highly symmetric theories that naturally, i.e. without
a high degree of fine-tuning, lead to the Standard Model at low energies and satisfy the extremely stringent experimental constraints on
any new physics. Also, one would like to keep the amount of (heavy) new particles that it will lead to to a minimum
and it should offer explanations for several features of the SM that seem accidental, such as the mixing patterns in the quark
and the lepton sector, the mass values and hierarchies, the approximate global symmetries, and the number of families or generations.
All these beg an explanation but it is very hard to find a simple and satisfactory one, while it is much less hard to find far-fetched or intricate ones.
The difficulty of finding a natural extension of the SM could be viewed as "The fine-tuning problem of physics beyond the
Standard Model": how does such a diverse SM arise at low energies from a not very elaborate and not precisely adjusted theory at high energies?
Scientific output:
- M. Petz, "SO(10) grand unification and its path to the Standard Model", MSc thesis 2025.
- J. Keuning, "Leptoquarks in an SO(10) Grand Unified Theory", MSc thesis 2024.
- G. Wortelboer, "Searching for TeV-scale leptoquarks in Grand Unified Theories", MSc thesis 2023.
- R. Peeters, "Aspects of fine-tuning in theories with extended scalar sectors", PhD thesis 2021.
- Simone Biondini, Daniël Boer, Ruud Peeters, "Hierarchy problem and fine-tuning in a decoupling approach to
multi-scale effective potentials", Physical Review D 104 (2021) 036013.
- Daniël Boer, Ruud Peeters, Sybrand Zeinstra, "Fine-tuning in models with extended Higgs sectors", Nuclear
Physics B 946 (2019) 114695.
- J. Thole, "SO(10) GUTs and flavor symmetries", MSc thesis 2019.
- A. Touwen, "Extending symmetries of the Standard Model towards Grand Unification", MSc thesis 2018.
- S. Zeinstra, "Studies of fine-tuning in extended Higgs models", MSc thesis 2018.
- S. van der Woude, "Asymptotic safety and restoration of conformal symmetry", MSc thesis 2017.
- Wouter Dekens, "Discrete symmetry breaking beyond the Standard Model", PhD thesis 2015.
- W. Dekens and D. Boer, "Viability of minimal left–right models with discrete symmetries", Nuclear Physics B 889 (2014) 727.
- Wouter Dekens, "A4 family symmetry", MSc thesis 2011.
Funding:
My research on this topic has in part been financially supported by the Dutch funding agency NWO and the Ubbo Emmius Fund of the University of Groningen.