Projected ATLAS Electron and Photon Trigger Performance in Run 3

ATLAS electron and photon triggers covering transverse energies from 4.5 GeV to several TeV are essential to record signals for a wide variety of physics: from Standard Model processes to searches for new phenomena. During Run-3 (2021-2024) main triggers used for those physics studies will be a single-electron trigger with ET threshold around 25 GeV and a diphoton trigger with thresholds at 25 and 35 GeV. Relying on these simple general-purpose triggers is a robust strategy that has already been tested during Run-2 (2015–2018) and avoids using a large number of analysis-specific triggers, albeit at the cost of slightly higher trigger output rates. In preparation for Run-3 data-taking, the Level-1 trigger hardware of the ATLAS calorimeter is being upgraded and the trigger software is being migrated to the multi-threaded AthenaMT framework. Impact from these modifications on the electron and photon triggers as well as their projected performance in Run-3 is presented.