Data Economy and Zero Suppression of the Liquid Argon Calorimetry Record

Initial estimates indicate that the ATLAS event size is roughly 2 MB, with the LAr data corresponding to 70% of the record. In this document two methods of reducing the contribution of the LAr calorimetry to the overall ATLAS data size are described. The first method simply recognizes that very low energy cells require less space in the record. The second method, called zero suppression, saves space in the LAr data recordby suppressing cells containing electronic and pileup noise. Using these two methods, reductions in the size of the LAr data record by a factor of approximately five to six can be achieved without obvious impairment of the underlying physics. The data reduction takes place in the RODs. The zero suppression algorithms are constructed to work either in the RODs or in the Event Filter. Information on how to run the zero suppression code are given and a sketch of a possible data format for the LAr data record is given. Last, but not least details are given of planned future upgrades to the zero suppression procedures.