Study of calorimeter calibration with pions from jets in CMS

We propose to use the single, isolated pions from QCD jet events for in situ calibration of the CMS calorimetry applying the E/p method. Due to the large jet cross sections at LHC the number of isolated pions from jet fluctuations is remarkable. Part of these pions pass ECAL without interaction while the major part of them starts the shower in ECAL. Using the fine granularity of the crystal calorimeter the sample of interacting pions can be cleaned from neutral particle contamination. An instantaneous luminosity of 10^33 cm-2 s-1 is assumed and the study is restricted to the barrel part of the calorimetry. We show that every HCAL tower can be calibrated with pions not interacting in ECAL with an accuracy of 1% with less than one month of data taking at the pion energies between 15-70 GeV. Using pions interacting in ECAL less than two months are required to achieve a 2% calibration error for every ECAL+HCAL trigger tower at the energies of 15-70 GeV.