The Level-1 Calorimeter Trigger (L1Calo) is a hardware-based pipelined system processing signals from the liquid-argon (LAr) and scintillating tiles (Tile) calorimeters and provides trigger signals to the Central Trigger Processor (CTP). It identifies events containing calorimeter-based physics objects, including electrons, photons, taus, jets, and missing transverse momentum. In preparation for Run 3, when the LHC is expected to run at higher energy and instantaneous luminosity, L1Calo and LAr are implementing a significant upgrade programme, in order to better perform in a challenging high-luminosity and high-pileup environment.
The existing hardware will be replaced by a new system of feature extractor modules, which will process finer LAr granularity information and execute more sophisticated algorithms to identify physics objects.