A fermionic top partner: Naturalness and the LHC

Joshua Berger, Jay Hubisz, Maxim Perelstein

Research output: Contribution to journalArticlepeer-review

76 Scopus citations


Naturalness demands that the quadratic divergence of the one-loop top contribution to the Higgs mass be cancelled at a scale below 1TeV. This can be achieved by introducing a fermionic (spin-1/2) top partner, as in, for example, Little Higgs models. In this paper, we study the phenomenology of a simple model realizing this mechanism. We present the current bounds on the model from precision electroweak fits, flavor physics, and direct searches at the LHC. The lower bound on the top partner mass from precision electroweak data is approximately 500 GeV, while the LHC bound with 5fb-1 of data at √s = 7TeV is about 450GeV. Given these bounds, the model can incorporate a 125GeV Higgs with minimal fine-tuning of about 20%. We conclude that natural electroweak symmetry breaking with a fermionic top partner remains a viable possibility. We also compute the Higgs decay rates into gauge bosons, and find that significant, potentially observable deviations from the Standard Model predictions may occur.

Original languageEnglish (US)
Article number16
JournalJournal of High Energy Physics
Issue number7
StatePublished - 2012


  • Beyond Standard Model
  • Higgs physics
  • Technicolor and composite models

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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