Search for a high mass diphoton resonance using the ATLAS detector

A search for resonances decaying to two photons was conducted with the ATLAS Experiment at the LHC. The analysis used proton-proton collision data with a center-of-mass energy of sqrt(s)=13 TeV and an integrated luminosity of 3.2/fb. Searches were performed for spin-0 particles at masses greater than 200 GeV and spin-2 particles at masses greater than 500 GeV. Limits on the production cross-section times branching ratio to two photons for both resonance types were computed. The largest local deviations from the background-only hypothesis are observed at a diphoton invariant mass of 750 GeV and correspond to 3.9 and 3.8 standard deviations for the spin-0 and spin-2 hypotheses, respectively. The global significances of the excesses of events are both 2.1 standard deviations.