Abstract
We compute the decay widths for the neutral and singly-charged Higgs bosons in the Georgi-Machacek model into the final states $\gamma\gamma$, $Z\gamma$, and $W\gamma$. These decays are most phenomenologically interesting for the fermiophobic custodial fiveplet states $H_5^0$ and $H_5^{\pm}$ when their masses are below threshold for decays into $WW$, $ZZ$, or $WZ$. We study the allowed branching ratios into these final states using scans over the allowed parameter space, and show how the model can be constrained by LEP searches for a fermiophobic Higgs boson decaying to two photons. The calculation involves evaluating one-loop diagrams in which the loop contains particles with two different masses, some of which do not appear in the existing literature. We give results for these diagrams in a form convenient for numerical implementation using the LoopTools package.
Highlights
Since the discovery of a Standard Model (SM)-like Higgs boson at the CERN Large Hadron Collider (LHC) [1], there has been considerable interest in models with extended Higgs sectors to be used as benchmarks for LHC searches for physics beyond the SM
We impose an upper bound on sin θH as a function of m5 determined in Ref. [25] from an ATLAS measurement of the like-sign WW cross section in vector boson fusion at the 8 TeV LHC [71], which would be increased by Hþ5 þ production
We require that m3, m5 ≥ 76 GeV; the lower bound on m5 was found in Ref. [37] based on an ATLAS search for anomalous like-sign dimuon production at 8 TeV [72,73], and the lower bound on m3 comes from the Large Electron-Positron (LEP) search for charged Higgs pair production in the Type I two Higgs doublet model [74], where we require m3 ≤ m5 to prevent off-shell decays Hþ3 → Hþ5 Z; H05Wþ
Summary
Since the discovery of a Standard Model (SM)-like Higgs boson at the CERN Large Hadron Collider (LHC) [1], there has been considerable interest in models with extended Higgs sectors to be used as benchmarks for LHC searches for physics beyond the SM. Our goal in this paper is to compute the loop-induced decay widths of the scalars in the GM model and study their behavior over the model’s parameter space, focusing on scalar masses below 200 GeV This is made nontrivial by the fact that some diagrams appear in the decays H05 → Zγ and HÆ5 → WÆγ that have not previously been computed in the literature. By contributing to H05 → Zγ, the new diagrams can affect the branching ratio of H05 → γγ (though we find that the effect is numerically small) We compute these new loop diagrams and give explicit results as integrals over Feynman parameters as well as in terms of the one-loop Passarino-Veltman integrals in the notation used by the LOOPTOOLS package. Appendix D we give some details of the calculations in the ’t Hooft-Feynman gauge of processes involving Goldstone bosons or ghosts
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