Variations of little Higgs models and their electroweak constraints

By C. Csáki, J. Hubisz, G. Kribs, Patrick Meade, J. Terning. 2003

184 citations recorded by the source corpus.

We calculate the tree-level electroweak precision constraints on a wide class of little Higgs models including variations of the littlest Higgs SU(5)/SO(5), SU(6)/Sp(6), and $\mathrm{SU}{(4)}^{4}/\mathrm{SU}{(3)}^{4}$ models. By performing a global fit to the precision data we find that for generic regions of the parameter space the bound on the symmetry breaking scale f is several TeV, where we have kept the normalization of f constant in the different models. For example, the ``minimal'' implementation of SU(6)/Sp(6) is bounded by $fg3.0\mathrm{TeV}$ throughout most of the parameter space, and $\mathrm{SU}{(4)}^{4}/\mathrm{SU}{(3)}^{4}$ is bounded by ${f}^{2}\ensuremath{\equiv}{f}_{1}^{2}{+f}_{2}^{2}g(4.2\mathrm{TeV}{)}^{2}.$ In certain models, such as $\mathrm{SU}{(4)}^{4}/\mathrm{SU}{(3)}^{4},$ a large f does not directly imply a large amount of fine-tuning since the heavy-fermion masses that contribute to the Higgs boson mass can be lowered below f for a carefully chosen set of parameters. We also find that for certain models (or variations) there exist regions of parameter space in which the bound on f can be lowered into the range 1\char21{}2 TeV. These regions are typically characterized by a small mixing between heavy and standard model gauge bosons and a small (or vanishing) coupling between heavy U(1) gauge bosons and light fermions. Whether such a region of parameter space is natural or not is ultimately contingent on the UV completion.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/5f29d4c4002398ab08146e774777b192a30cd4e2

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Citations in the corpus

T parity and the littlest Higgs (2004, background): “There are many variants of the little Higgs models [13, 14, 15, 16, 17, 18], as well as some examples of UV extensions above 10 TeV [19, 20], and extensive phenomenological studies have been performed [21, 22, 23, 24, 25, 26, 27, 28, 29].”
LITTLE HIGGS THEORIES (2005, background): “[40] also analyzed contributions to precision electroweak observables in the SU(3) model, and found the constraint f > 4 TeV; however, in this case, the mass of the heavy fermion may be well below f , and so it is possible to have only mild fine tuning even with large values of f .”
Little hierarchy, little higgses, and a little symmetry (2004, methodology): “The electroweak observables also receive contributions from the new TeV particles in little Higgs theories, and there have been several studies on this issue for various little Higgs models [19, 20, 21, 22, 23, 24, 25, 26, 27].”