Interpreting the 750 GeV diphoton excess within topflavor seesaw model

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