Minimal conformal technicolor and precision electroweak tests
Abstract
We study the minimal model of conformal technicolor, an SU(2) gauge theory near a strongly coupled conformal fixed point, with conformal symmetry softly broken by technifermion mass terms. Conformal symmetry breaking triggers chiral symmetry breaking in the pattern SU(4) → Sp(4), which gives rise to a pseudoNambuGoldstone boson that can act as a composite Higgs boson. The top quark is elementary, and the top and electroweak gauge loop contributions to the Higgs mass are cut off entirely by Higgs compositeness. In particular, the model requires no top partners and no “little Higgs” mechanism. A nontrivial vacuum alignment results from the interplay of the top loop and technifermion mass terms. The composite Higgs mass is completely determined by the top loop, in the sense that m _{ h }/ m _{ t } is independent of the vacuum alignment and is computable by a strongcoupling calculation. There is an additional composite pseudoscalar A with mass larger than m _{ h } and suppressed direct production at LHC. We discuss the electroweak fit in this model in detail. Corrections to Z to bar{b}b and the T parameter from the top sector are suppressed by the enhanced Sp(4) custodial symmetry. Even assuming that the strong contribution to the S parameter is positive and usuppressed, a good electroweak fit can be obtained for v/ f ≲ 0 .25, where v and f are the electroweak and chiral symmetry breaking scales respectively. This requires fine tuning at the 10% level.
 Publication:

Journal of High Energy Physics
 Pub Date:
 October 2010
 DOI:
 10.1007/JHEP10(2010)086
 arXiv:
 arXiv:1001.1361
 Bibcode:
 2010JHEP...10..086E
 Keywords:

 Beyond Standard Model;
 Technicolor and Composite Models;
 High Energy Physics  Phenomenology
 EPrint:
 34 pages, 4 figures