Higher dimension operators for a composite Higgs


  • Call:

    IDPASC Portugal - PHD Programme 2019

  • Academic Year:

    2019 / 2020

  • Domain:

    Theoretical Particle Physics

  • Supervisor:

    Brigitte Hiller

  • Co-Supervisor:

    Alex Blin

  • Institution:

    Universidade de Coimbra

  • Host Institution:

    Universidade de Coimbra

  • Abstract:

    The announcement of the discovery of a Higgs boson in 2012 at the CERN Large Hadron Collider has been since then succeeded by numerous measurements to confirm its properties in terms of the Standard Model. To present date some deviations in its couplings are possible at the level of about ten percent, leaving open a window for extensions of the Higgs sector [1]. One of the venues is to admit a composite Higgs in terms of quark substructures associated to a dynamically generated top antitop condensate at the electroweak scale, in a Nambu- Jona-Lasinio (NJL) like mechanism [2], where a scalar boson emerges with a mass twice as large as the top quark. Confronted with the values of the top quark and Higgs masses presently known, one must however conclude that they are not compatible with that prediction, even after considering the associated renormalization group (RG) evolution. We propose to take into account higher dimension multiquark operators, which are known to allow a reduction in the mass of the scalar isoscalar meson sigma in the low energy spectrum of QCD, resulting from chiral symmetry breaking instead [3]. Due to the universal character of dynamical symmetry breaking phenomena, similar effects may be expected at different scales. The inclusion of the higher dimension operators requires a careful reformulation of the Higgs sector dynamics and couplings, starting from a classification of those interactions relevant at the pertinent scale, within an effective Lagrangian approach, and how they impact on the related Higgs production and decay rates, the gauge bosons and rho parameter, fermion families and RG equations. Bibliography: [1] H. E. Logan, TASI 2013 lectures on Higgs physics within and beyond the Standard Model, arXiv:1406.1786 [hep-ph]. [2] William A. Bardeen, Christopher T. Hill, and Manfred Lindner, Phys. Rev. D41 (1990) 1647. [3] A. A. Osipov, B. Hiller, A. H. Blin , J. da Providência, Annals Phys. 322 (2007) 2021-2054.