Higgs singlet boson as a diphoton resonance in a vector-like quark model

ATLAS and CMS recently showed the first results from run 2 of the Large Hadron Collider (LHC) at √s=13 TeV. A resonant bump at a mass of around 750 GeV in the diphoton invariant mass spectrum was indicated and the corresponding diphoton production cross section is around 3-10 fb. Motivated by the LHC diphoton excess, we propose that the possible resonance candidate is a Higgs singlet. To produce the Higgs singlet via the gluon-gluon fusion process, we embed the Higgs singlet in the framework of the vector-like triplet quark (VLTQ) model. As a result, the Higgs singlet decaying to the diphoton final state is via VLTQ loops. Using the enhanced number of new quarks and new Yukawa couplings of the VLTQs and Higgs singlet, we successfully explain the diphoton production cross section. We find that the width of the Higgs singlet is below 1 GeV, its production cross section can be of the order of 1 pb at √s=13 TeV, and the branching ratio for it decaying to a diphoton is around 0.017 and is insensitive to the masses of VLTQs and new Yukawa couplings. We find a strong correlation between the Higgs Yukawa couplings to s-b and c-t; the resulted branching ratio for t→ch can be 1.1×10^-4 when the constraint from B_s oscillation is applied. With the constrained parameter values, the signal strength for the standard model Higgs decaying to a diphoton is μγγ<1.18, which is consistent with the current measurements at ATLAS and CMS.