Calibration of photomultipliers and initial adjustment of the LHCb Electromagnetic Calorimeter for pilot LHC runs

The procedure for the initial adjustment of the LHCb ECAL energy scale is described. The calibration technique to determine the gains of photomultipliers in situ is discussed in details, including its technical implementation and the studies on possible systematic effects. Finally, the di-photon invariant mass distributions from early data collected in the end of 2009 in the course of the LHC start-up are presented, proving the sufficient level of the initial cell-to-cell intercalibration to detect clear signal from $\pi^0 \to \gamma \gamma$ decays