First study of the LVL2-EF boundary in the high-pT electron/photon High-Level Trigger

In the ATLAS High-Level Trigger (HLT), the Level-2 and Event Filter stages can be seen as a set of modular selection algorithms that can migrate between the two trigger levels. This note presents results of a first study of the Level-2/Event Filter boundary for theelectron and photon triggers, including possible HLT strategies. Also shown are results on the use of sequential selection at the Event Filter, LVL2-seeding of the EF, the migration of LVL2 algorithms steps, and an evaluation of the signal and background overlaps of the LVL2 and EF selections.