https://doi.org/10.1140/epjc/s10052-008-0771-7
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
* e-mail: cyn@general.elte.hu
Received:
23
June
2008
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
