Simulation of the diphoton mass spectrum for a Higgs boson with a mass of 120 GeV/c² decaying into two photons. The mass resolution of the diphoton channel is extremely good compared to dijet decay modes (Gaussian sigma / mean < 3 % ).

Central diphoton signal acceptance, in percent, for each signal process and mass point generated.

No significant narrow resonance is observed in the data. A smooth fit is made to the diphoton invariant mass distribution of the data using sidebands for each Higgs test mass and then interpolating to the signal region of that test mass. The fit in the signal region is used to establish the background expectation. The data vs. fit residual is shown for a Higgs test mass of 120 GeV/c².

95% C.L. upper limits are set on the production cross section times branching fraction relative to the standard model prediction using a Bayesian binned likelihood approach.

Invariant mass distribution of the data compared to the background model with a Higgs signal of 120 GeV/c² scaled to both its expected and observed limits.