Phenomenology of a 750 GeV singlet

We study the recently reported excess in the diphoton resonance search by atlas and cms. we investigate the available parameter space in the combined run-1 and run-2 diphoton data and study its interpretation in terms of a singlet scalar field which possibly mixes with the standard model higgs boson. we show that the mixing angle is already strongly constrained by high-mass higgs searches in the diboson channel, and by higgs coupling measurements. while a broad resonance is slightly favored, we argue that the signal is consistent with a narrow-width singlet which couples to colored and electromagnetically-charged vector-like fermions. dijet signals are predicted and be visible in upcoming analyses. allowing for additional decay modes could explain a broader resonance, however, we show that monojet searches disfavor a large invisible width. finally, we comment on the possible relation of this scenario to the naturalness problem.