Ricerc@Sapienza

ELI-NP is an European Research Infrastructure that will provide a monochromatic,high brilliance gamma beam with tunable energy up to 19.5 MeV. The time structure of the beamconsists of 32 high intensity gamma bunches separated by a time interval of 16 ns and deliveredat a repetition rate of 100 Hz. In order to match such unprecedented beam specifications, specificdevices and techniques have been developed to measure and monitor the beam parameters duringthe commissioning and the operational phase.

This paper presents the electron and photon energy calibration obtained with the ATLAS detector using about 36 fb(-1) of LHC proton-proton collision data recorded at root s = 13 TeV in 2015 and 2016. The different calibration steps applied to the data and the optimization of the reconstruction of electron and photon energies are discussed. The absolute energy scale is set using a large sample of Z boson decays into electron-positron pairs.