Abstract
We propose that the extension of the Standard Model by typical vector-like SU(2)L doublet fermions and non-singlet scalar field can account for the observed 750 GeV diphoton excess in experimentally allowed parameter space. Such an idea can be realized in a typical topflavor seesaw model where the new resonance X is identified as a CP-even or CP-odd scalar emerging from a certain bi-doublet Higgs field, and it can couple rather strongly to photons and gluons through mediators such as vector-like fermions, scalars as well as gauge bosons predicted by the model. Numerical analysis indicates that the model can predict the central value of the diphoton excess without contradicting any constraints from 8 TeV LHC. Among all the constraints, the tightest one comes from the Zγ channel with σ8 TeVZγ≲3.6 fb, which requires σ13 TeVγγ≲6 fb in most of the favored parameter space. Theoretical issues such as vacuum stability and Landau pole are also addressed.
Highlights
In the searches for new physics at the LHC Run-II with √ s =13TeV and fb−1 integrated data, both the ATLAS and CMS collaborations reported a diphoton excess with an invariant mass around 750 GeV [1, 2]
We propose to interpret the 750 GeV diphoton excess in a typical topflavor seesaw model
The new resonance X can be identified as a CP-even scalar emerging from a certain bidoublet higgs field
Summary
We introduce new vector-like fermions and split their mass spectrum by seesaw mechanism [21] In this way, the 750GeV resonance is identified as a CP-even scalar emerging from a bi-doublet Higgs, which triggers the breaking of the two SU(2) gauge symmetry into SU (2)L, and its interactions with photons are induced by relevant scalars, fermions as well as gauge bosons. The 750GeV resonance is identified as a CP-even scalar emerging from a bi-doublet Higgs, which triggers the breaking of the two SU(2) gauge symmetry into SU (2)L, and its interactions with photons are induced by relevant scalars, fermions as well as gauge bosons Due to these features, our model has more freedom to explain the diphoton excess than the minimal model. We present more details of our model in the Appendix
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