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Alternatives to the Standard Higgs Model

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In particle physics, a Higgsless model is a model that does not involve the Higgs boson or in which the Higgs field is not dynamical. Such models must employ a different mechanism of mass generation, electroweak symmetry breaking and unitarity.

In the years since the Higgs mechanism was first described, there have been several alternatives proposed. All of the alternative mechanisms use strongly interacting dynamics to produce a vacuum expectation value that breaks electroweak symmetry. A partial list of these alternative mechanisms includes:

  • Technicolor[1] is a class of models that attempts to mimic the dynamics of the strong force as a way of breaking electroweak symmetry. In this model, the Higgs boson is not a fundamental particle but a condensate of new particles bound together by a new strong force similar to QCD, but with a rescale characteristic energy scale.
  • Extra dimensional Higgsless model is a class of model where the fifth component of the gauge fields play the role of the Higgs fields. In this way it is possible to describe a realistic symmetry breaking pattern originated by boundary conditions to the extra dimensional fields and a delay of the unitarity breakdown scale up to the energy of the discovered extra dimension.[2][3] Through the AdS/QCD correspondence this models can be seen as related to the technicolor model and to the UnHiggs mechanism, where the Higgs field is of unparticle nature.[4]
  • Models of composite W and Z vector bosons.[5]
  • Top quark condensate.
  • "Unitary Weyl gauge". In λ go to zero limit the sigma model is scale invariant, and if one further adds a suitable gravitational term to the action, the theory becomes locally scale invariant (i.e. Weyl invariant). Weyl transformations act multiplicatively on the Higgs field, so one can fix the Weyl gauge by requiring that the Higgs field to be constant.[6]
  • Asymptotic safety of some nonlinear sigma models.[7]

References

  1. ^ Dimopoulos, S.; Susskind, L. (1979), "Mass Without Scalars", Nuclear Physics B, 155 (1): 237–252, doi:10.1016/0550-3213(79)90364-X
  2. ^ Csaki, C.; Grojean, C.; Pilo, L.; Terning, J. (2004), "Towards a realistic model of Higgsless electroweak symmetry breaking", Physical Review Letters, 92 (10): 101802, doi:10.1103/PhysRevLett.92.101802, arXiv:hep-ph/0308038
  3. ^ Csaki, C.; Grojean, C.; Pilo, L.; Terning, J. (2004), "Gauge theories on an interval: Unitarity without a Higgs", Physical Review D, 69 (5): 055006, doi:10.1103/PhysRevD.69.055006, arXiv:hep-ph/0305237
  4. ^ Calmet, X.; Deshpande, N. G.; He, X. G.; Hsu, S. D. H. (2008), "Invisible Higgs boson, continuous mass fields and unHiggs mechanism", Physical Review D, 79 (5): 055021, doi:10.1103/PhysRevD.79.055021, arXiv:0810.2155
  5. ^ Abbott, L. F.; Farhi, E. (1981), "Are the Weak Interactions Strong?", Physics Letters B, 101 (1–2): 69, doi:10.1016/0370-2693(81)90492-5
  6. ^ Pawlowski, M.; Raczka, R. (1994), "A Unified Conformal Model for Fundamental Interactions without Dynamical Higgs Field", Foundations of Physics, 24 (9): 1305–1327, doi:10.1007/BF02148570, arXiv:hep-th/9407137
  7. ^ Codello, A.; Percacci, R. (2008), "Fixed Points of Nonlinear Sigma Models in d>2", Physics Letters B, 672 (3): 280–283, doi:10.1016/j.physletb.2009.01.032, arXiv:hep-th/0810.0715


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