Phisymmetry in 2011 Phisymmetry was used: L1 Prerequisite: L1_BscMinBiasOR_BptxPlusANDMinus (before May technical stop) L1_ZeroBias (after May technical stop) 150 Mev (EB) HLT requests: single crystal energy deposit > [noise suppression] 650 Mev (EE) Rate: 500 Hz Badwidth: ~1.9 MB/s Phisymmetry was used: to derive IC value in combination with pi0/eta to monitor the stability of the calorimeter calibration COMPARISON OF TWO IC SETS (TWO DIFFERENT PERIODS) TOOL TO DETECT PROBLEMATIC REGIONS It is still the only method which can provide a calibration at the single crystal level in short time (2-3 days at the end of 2011)

Use of phisymmetry data in 2012 (I) The absolute precision of phisymmetry ~1.5% in central EB, poor respect to other methods. But in the difference (or the ratio) of the ICs, systematic errors largely cancel out and the residual distribution spread is the statistical error + the instability of the crystal. The statistical error on the ratio of the ICs was evaluated analyzing the RUN2010A data where the crystal instability is assumed to be negligible Relative precision from run 2010A: - 0.5% from 200 Mevt - 0.2% systematic limit This makes phisymmetry a powerful tool to detect and correct regions with problematic calibration values and to make fine-grained checks of ECAL laser corrections

Use of phisymmetry data in 2012 (II) Precision of the IC ratio: Assuming c=0.18, s=7.2 (from previous slide) and <NPU>=~15: In October few runs taken at higher rate (1.5 kHz) but data spread out in several days. Analysis ongoing but difficult to cross check the laser correction using this data. Proposal: start 2012 with higher phisymmetry rate (at least 1.5 kHz)