Search for new phenomena in high-mass diphoton final states with ATLAS at $\sqrt{\textrm{s}}$ =13 TeV

Abstract

After the discovery of the Higgs boson, one of the most important tasks of high energy physics at the LHC is to look for signatures of new physics beyond the Standard Model. Various extensions of the Standard Model predict the existence of new high-mass states that decay into two photons, and the experimental observation of such states would be a first evidence of new physics. This search is currently ongoing in the ATLAS experiment at the Large Hadron Collider. The analysis is based on proton-proton collision data corresponding to an integrated luminosity of 36.7 $\textrm{fb}^{-1}$ at $\sqrt{\textrm{s}}$ = 13 TeV recorded in 2015 and 2016. Two different studies are performed, one targeted at the search for a spin-2 particle, using Randall-Sundrum or ADD extra-dimension model as benchmark models, and one optimized for a spin-0 particle. The observed diphoton invariant mass spectrum in both studies is in good agreement with the expected Standard Model background.