The European Physical Journal C

, Volume 58, Issue 3, pp 463–469 | Cite as

Electroweak precision constraints on vector-like fermions

  • G. Cynolter
  • E. Lendvai
Regular Article - Theoretical Physics


We calculate the oblique electroweak corrections and confront them with the experiments in an extension of the standard model. The new fields added are a vector-like weak doublet and a singlet fermion. After electroweak symmetry breaking there is a mixing between the components of the new fields, but there is no mixing allowed with the standard fermions. Four electroweak parameters, \(\hat{S}\) , \(\hat{T}\) , W and Y, are presented in the formalism of Barbieri et al.; these are the generalization of the Peskin–Takeuchi S, T and U. The vector-like extension is slightly constrained. \(\hat{T}\) requires the new neutral fermion masses not to be very far from each other, allowing for higher mass differences for higher masses and smaller mixing. \(\hat{S}\) , W and Y give practically no constraints on the masses. This extension can give a positive contribution to \(\hat{T}\) , allowing for a heavy Higgs boson in electroweak precision tests of the standard model.


Dark Matter Higgs Boson Electroweak Symmetry Breaking Electroweak Precision Custodial Symmetry 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag / Società Italiana di Fisica 2008

Authors and Affiliations

  1. 1.Theoretical Physics Research Group of Hungarian Academy of SciencesEötvös UniversityBudapestHungary

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