ECAL Barrel Intercalibration at Low Luminosity

The purpose of this study is to give the order of magnitude of the time necessary to intercalibrate barrel crystals when LHC starts with a very low luminosity ( 10E-32 cm-2s-1). In this note, we will examine the use of isolated electromagnetic clusters from pi0 or eta or other photon and electron sources. This study does not use the mass reconstruction of the particle ( pi0, eta, ...). It is based on the intercalibration of crystals which belong to a same pseudorapidity interval, assuming that the crystal deposited energy distributions are independent of the azimuth phi.