Laser calibration of the ATLAS Tile Calorimeter during LHC Run 2

This article reports the laser calibration of the hadronicTile Calorimeter of the ATLAS experiment in the LHC Run 2 datacampaign. The upgraded Laser II calibration system is described. Thesystem was commissioned during the first LHC Long Shutdown,exhibiting a stability better than 0.8% for the laser lightmonitoring. The methods employed to derive the detector calibrationfactors with data from the laser calibration runs are alsodetailed. These allowed to correct for the response fluctuations ofthe 9852 photomultiplier tubes of the Tile Calorimeter with a totaluncertainty of 0.5% plus a luminosity-dependent sub-dominantterm. Finally, we report the regular monitoring and performancestudies using laser events in both standalone runs and during protoncollisions. These studies include channel timing and qualityinspection, and photomultiplier linearity and response dependence onanode current.