All seminars will take place in the room "Grande Ourse", Bâtiment 13, 1st floor.

Organisers : Michele Frigerio, Marc Knecht, Jean-Loïc Kneur

• Wednesday 6 December
  • 15:00 Gabriele Ferretti
    UV-complete composite Higgs models and their collider signatures
    

    

    Abstract : We present a class of four-dimensional strongly-coupled gauge theories in which the Higgs boson arises as a pseudo-Nambu-Goldstone boson and top-partners arise as bound states of three hyperfermions. All models have additional pNGBs in their spectrum that could be accessible at the LHC. We discuss the experimental signatures that can be expected from these models, concentrating on those that are common to all models in this class, particularly a light "axion-like" pseudoscalar. We also comment how the Lattice can help answering some of the questions about their strong coupling dynamics.

  • 17:00 David Schaich
    Lattice gauge theory at the electroweak scale

    

    Abstract : Lattice gauge theory is a non-perturbative framework that enables numerical analyses of strongly interacting quantum field theories from first principles. This approach is broadly applicable, and in this talk I will discuss lattice studies beyond QCD, in the context of new strong dynamics at the electroweak scale. After a high-level overview of lattice gauge theory I will focus on the non-perturbative beta functions, anomalous dimensions, and composite spectra of strongly coupled near-conformal systems. Time permitting I will more briefly mention additional topics for discussion, including electroweak precision observables and composite dark matter.

• Thursday 7 December
  • 10:00 Maurizio Piai
    Hierarchy of scales in strongly-coupled theories

    

    Abstract : In the context of gauge/gravity dualities, we calculate the scalar and tensor mass spectrum of the boundary theory defined by a special 8-scalar sigma-model in five dimensions, the background solutions of which include the 1-parameter family dual to the baryonic branch of the Klebanov-Strassler field theory. This provides an example of a strongly-coupled, multi-scale system that yields a parametrically light mass for one of the composite scalar particles : the dilaton. We briefly discuss the implications of these findings towards identifying a satisfactory solution to both the big and little hierarchy problems of the electro-weak theory.

  • 14:00 Discussion on strong dynamics at the electroweak scale with a 30-minutes talk by Nicolas Bizot
    Analysis of the spectrum of composite resonances

    

    Abstract : We consider one of the minimal vector-like gauge theory of fermions that confines at the multi-TeV scale, and that realizes the Higgs particle as a composite pseudo-Nambu Goldstone boson (pNGB). The pNGB Higgs arises from the spontaneous breaking of a SU(4) flavour symmetry down to Sp(4). Using non-perturbative techniques à la Nambu and Jona-Lasinio (NJL), we estimate the masses of the composite mesons as well as the Goldstone decay constant f. These techniques have been often used in the past for QCD and are based on a 1/N expansion. In order to supply composite top-quark partners and to realise the partial compositeness paradigm, the theory should contain an additional sector with flavour symmetry-breaking pattern SU(6)/SO(6). We identify and analyse several non-trivial features of the complete two-sector gauge theory. Finally, we briefly comment on the computation of the trilinear baryon masses that can be very useful as inputs parameters for more phenomenological analysis. We also comment on few possible interesting directions that can be explored within the NJL framework.

  • 16:00 Javi Serra
    Top quark partners : alternative scenarios and their phenomenology

    

    Abstract : Symmetries have shaped the way we address the limitations of the Standard Model (SM). This is particularly true for solutions to the electroweak hierarchy problem, where Composite Higgs models (but also Supersymmetry), crucially rely on symmetries to conform with observations. I will discuss the last example of this philosophy, in which the top partners, the prime sign of naturalness in these theories, solve the little hierarchy problem while being neutral under the SM gauge symmetries.

• Friday 8 December
  • 10:00 Alex Pomarol
    Holography for models of compositeness

    

    Abstract : I will present a brief introduction of how to use holography to construct models of composite particles, showing the similarities with QCD-like theories. I will then concentrate on models of composite Higgs, explaining the main novel features emerging from holography. Finally, I will present an holographic approach to theories close to the conformal transition, trying to understand the presence of light scalars as recent lattice simulations seem to suggest.