Relative pre-calibration of the ALICE electromagnetic calorimeter EMCAL

Several experiments showed that calorimetry is an essential tool for the Quark-Gluon Plasma study. ALICE, on the LHC collider, therefore integrated two electromagnetic calorimeters in its design. We will explain how the relative pre-calibration of one of them, the EMCAL, is performed thanks to cosmic muons, through an iterative procedure which consists in varying the high-voltage associated to each channel to ajust its gain. After 3 iterations of high-voltage tuning, of which each requires a day of data-taking, the dispersion (RMS over mean) of the channel amplitude of the response to a muon at minimum ionisation is found to be less than 2 %. We also show that more iterations allow to lower this value down to 1 %.