Constraining the littlest Higgs
Abstract
Little Higgs models offer a new way to address the hierarchy problem, and give rise to a weaklycoupled Higgs sector. These theories predict the existence of new states which are necessary to cancel the quadratic divergences of the Standard Model. The simplest version of these models, the Littlest Higgs, is based on an SU(5)/SO(5) nonlinear sigma model and predicts that four new gauge bosons, a weak isosinglet quark, t', with Q = 2/3, as well as an isotriplet scalar field exist at the TeV scale. We consider the contributions of these new states to precision electroweak observables, and examine their production at the Tevatron. We thoroughly explore the parameter space of this model and find that small regions are allowed by the precision data where the model parameters take on their natural values. These regions are, however, excluded by the Tevatron data. Combined, the direct and indirect effects of these new states constrain the `decay constant' f>~3.5 TeV and m_{t'}>~10 TeV. These bounds imply that significant finetuning be present in order for this model to resolve the hierarchy problem.
 Publication:

Journal of High Energy Physics
 Pub Date:
 October 2003
 DOI:
 10.1088/11266708/2003/10/062
 arXiv:
 arXiv:hepph/0211218
 Bibcode:
 2003JHEP...10..062H
 Keywords:

 Beyond Standard Model Technicolor and Composite Models;
 High Energy Physics  Phenomenology
 EPrint:
 31 pgs, 26 figures