# Calibration of the photon spectrometer PHOS of the ALICE experiment

## TL;DR

This paper details the calibration procedures for the PHOS photon spectrometer in the ALICE experiment, including gain, alignment, nonlinearity, and time-dependent corrections, to optimize energy resolution in proton-proton collisions.

## Contribution

It presents a comprehensive calibration methodology for the PHOS detector, improving energy measurement accuracy and resolution in high-energy physics experiments.

## Key findings

- Achieved mass resolutions of 4.56 MeV/c^2 for π^0 mesons
- Achieved mass resolutions of 15.3 MeV/c^2 for η mesons
- Demonstrated effective calibration corrections in pp collisions at 13 TeV

## Abstract

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 evaluate the geometrical alignment and the corresponding correction of the absolute energy scale, to obtain the nonlinearity 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 $\sqrt{s}$ = 13 TeV. After applying all corrections, the achieved mass resolutions for $\pi^0$ and $\eta$ mesons for $p_{\rm{T}} > 1.7$ GeV/$c$ are $\sigma_m^{\pi^0} = 4.56 \pm 0.03$ MeV/$c^2$ and $\sigma_m^{\eta} = 15.3 \pm 1.0$ MeV/$c^2$, respectively.