Performance of the ALICE electromagnetic calorimeters in LHC Runs 1 and 2 and upgrade projects

Abstract

ALICE (A Large Ion Collider Experiment) at the LHC is designed for studies of nuclear matter at extreme temperatures and energy densities, the so-called Quark-Gluon Plasma (QGP). Two detectors for measurements of electromagnetic signals, high-granularity photon spectrometer PHOS and large acceptance electromagnetic calorimeter EMCal/DCal, are incorporated into the ALICE detector. In order to enhance the data sample of the high-energy part of the spectra, dedicated triggers on high energetic photons or jets are used. High precision measurements of neutral mesons require fine energy and timing calibrations. Photon signal purity is improved using dedicated photon PID criteria based on cluster shape and anti-track matching with the ALICE central tracking system, as well as a special detector located in front of PHOS called CPV. PHOS and EMCal participated in LHC Run 1 (2009-2013) and Run 2 (2015-2018) during data taking periods of pp, p-Pb and Pb-Pb collisions. We give an overview of their performance in Runs 1 and 2 in low and high multiplicity environments as well as the upgrade plans for future LHC runs.