2014/04/30 by Katy Hartling, Kunal Kumar, Heather E. Logan · 1 citation
Physics and Astronomy · #hep-ph
paper · pdf · doi:10.1103/physrevd.90.015007
published as Phys. Rev. D 90, 015007 (2014) · 40 pages, 12 figures, v2 : typo in Eq. 61 corrected, Reference added, v3: typos in Eq. A8 line 2 and Eq. 28 corrected, version to be published in PRD
arxiv created 2014/07/11 · arxiv updated 2014/07/16
We study the most general scalar potential of the Georgi-Machacek model, which adds isospin-triplet scalars to the Standard Model (SM) in a way that preserves custodial SU(2) symmetry. We show that this model possesses a decoupling limit, in which the predominantly-triplet states become heavy and degenerate while the couplings of the remaining light neutral scalar approach those of the SM Higgs boson. We find that the SM-like Higgs boson couplings to fermion pairs and gauge boson pairs can deviate from their SM values by corrections as large as O(v2/M\rm new2), where v is the SM Higgs vacuum expectation value and M\rm new is the mass scale of the predominantly-triplet states. In particular, the SM-like Higgs boson couplings to W and Z boson pairs can decouple much more slowly than in two Higgs doublet models, in which they deviate from their SM values like O(v4/M\rm new4). Furthermore, near the decoupling limit the SM-like Higgs boson couplings to W and Z pairs are always larger than their SM values, which cannot occur in two Higgs doublet models. As such, a precision measurement of Higgs couplings to W and Z pairs may provide an effective method of distinguishing the Georgi-Machacek model from two Higgs doublet models. Using numerical scans, we show that the coupling deviations can reach 10% for M\rm new as large as 800~GeV.