Regular Article - Theoretical Physics
Electroweak precision constraints on vector-like fermions
Theoretical Physics Research Group of Hungarian Academy of Sciences, Eötvös University, 1117 Pázmány Péter sétány 1/A, Budapest, Hungary
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Revised: 5 September 2008
Published online: 23 October 2008
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, , , 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. 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. , W and Y give practically no constraints on the masses. This extension can give a positive contribution to , allowing for a heavy Higgs boson in electroweak precision tests of the standard model.
© Springer-Verlag , 2008