Interpreting the 750 GeV diphoton excess in minimal extensions of Two-Higgs-Doublet models

It is shown that the 750 GeV diphoton excess can be explained in extensions of Two-Higgs-Doublet Models that do not involve large multiplicities of new electromagnetically charged states. The key observation is that at moderate and large $\tan \beta$ the total decay width of the 750 GeV Higgs is strongly reduced as compared to the Standard Model. This allows for much more economical choices of new states that enhance the diphoton signal to fit the data. In particular, it is shown that one family of vector-like quarks and leptons with SM charges is enough to explain the 750 GeV diphoton excess. Moreover, such charge assignment can keep the 125 GeV Higgs signal rates exactly at the SM values. The scenario can interpret the diphoton excess provided that the total decay width of a hypothetical resonance that would be measured at the LHC turns out to not exceed few GeV.