A stand-alone signal reconstruction and calibration algorithm for the ATLAS electromagnetic calorimeter

The ATLAS Liquid Argon electromagnetic calorimeter uses a digital filtering technique to reconstruct the signal amplitude from the ionization pulse samplings; the digital filtering coefficients computation requires the knowledge of the ionization pulse profile in each cell. This ionization waveform must have the correct normalization with respect to the calibration pulse used to compute the actual electronic gain of each channel, thus taking into account the differences between the two waveforms, as well as and the different current paths in the detector. A stand-alone algorithm is developed to predict for each cell the ionization signal waveform, with the only use or the information obtained from the analysis of the corresponding calibration pulse. The advantage of this approach is that the proper gain of each channel and the corrections for the cell different electrical properties can be applied directly during the signal reconstruction phase, with no direct knowledge of the response of the cell to the shower-induced ionization current. The procedure is tested on the electron test-beam data taken from an EMC production module, proving the ability to reconstruct the energy with a response uniformity of 0.55%.