Calibration of the ALICE PHOS calorimeter

The procedure for the energy calibration of the high granularity electromagnetic calorimeter PHOS of the ALICE experiment is presented. The methods used to perform the relative gain calibration, to estimate the geometrical alignment and the corresponding correction of the absolute energy scale, to evaluate the non-linearity correction coefficients and finally, to calculate the time-dependent calibration corrections, are discussed and illustrated by the PHOS performance in proton-proton (pp) collisions at . After applying all corrections, the widths of π0 and η meson peaks at p T > 1.7 GeV/c σ π 0 = 4.51 ± 0.03 MeV/c2 and ση = 15.3 ± 1.0 MeV/c2, respectively, were achieved.