Abstract: This course is essentially divided into three parts. I first introduce the modern Effective Field Theory perspective on Quantum Field Theory. I discuss in particular the role of symmetries and the notion of naturalness, offering a critical analysis of the origin of hierarchical mass scale separations. In the second part I analyze in the light of those concepts the Standard Model, highlighting how its remarkable phenomenological adequacy structurally relies on a seemingly unnatural scale separation. In the third part, I present the two main extensions of the SM, Compositeness and Supersymmetry, capable of producing a natural scale
separation. I illustrate how these scenarios spoil the structural simplicity at the basis of the phenomenological adequacy of the SM and require somewhat ad hoc model building hypotheses. That creates a paradoxical tension between naturalness and simplicity, which defines in my mind the so-called hierarchy paradox. I will illustrate where past, present and future collider experiments stand in the exploration of this matter.
Behind & Beyond the Standard Model
1. Ideology
- The two modern perspectives on QFT: Effective Field Theory
and RG-flow
- Symmetries (with their accidentality), Selection rules &
Naturalness
- Critical analysis of scale separation in QFT (natural and
unnatural hierarchies)
2. The SM as an EFT (in its entirety not just as CERN’s T-shirt)
- the phenomenal structure of the renormalizable truncation
of the SM,
aka the T-shirt lagrangian.
(baryon& lepton number, flavor selection rules, custodial
symmetry)
-concrete illustration of the above: FCNC and CP violation
suppression, a quick view of precision
electroweak tests
- the Higgs sector and the difficulty to account for the scale
separation supporting the phenomenal
properties of the T-shirt lagrangian
3. Beyond the Standard Model and the Hierarchy paradox
- models that address (even partially) the natural origin of
scale separation: their plus and their minuses
- Supersymmetry
- Compositeness
- Naturalness vs Simplicity
- the relevance of collider experiments, present and future
- if interest exist I can give an additional lecture on a more
formal perspective on supersymmetric models
(soft supersymmetry breaking from the susy cfts
standpoint) |