Top-phobic heavy Higgs boson as the 750 GeV diphoton resonance

A hint of a new resonance at a mass of 750 GeV has been shown in the diphoton channel of the Run-2 LHC data. The observed signal rate is usually too large to interpret it as a new scalar boson in the context of weakly coupled renormalizable models. One way is to reduce its total decay rate, which is possible if the CP-even heavy Higgs boson H-0 in the aligned two Higgs doublet model becomes top-phobic. To ensure sufficient gluon fusion production, we introduce vector-like quarks (VLQ). The Higgs precision data as well as the exclusion limits from no excesses in other resonance searches through Z gamma, b (b) over bar, tau(+)tau(-), and jj channels at the Run-1 LHC are comprehensively studied. In Type I, the top-phobic H-0 cannot simultaneously explain the 750 GeV diphoton excess and the Higgs precision data since the same Yukawa couplings of the up-type and down-type VLQs to H-0 always make more contribution to the diphoton signal rate of the standard model Higgs boson than that of H-0. In Type II, small Yukawa coupling of the up-type VLQ but sizable Yukawa coupling of the down-type VLQ is shown to explain the signal while satisfying other LHC exclusion limits.