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I've suggested this before, but I'll try it again: Why segment the calorimeters at all? If we change the Gismo philosophy to recording hit positions instead of tower energies, then a later stage of processing can apply any segmentation size it likes. The compute intensive step is generating the hits. By comparison, assigning the hits to towers is cheap. Thus a study of segmentation size should be easy to accomplish. The standard objection is that dataset size will explode on us. I experimented with this by fudging gismo to believe that all particle hits were parentless, thus forcing each track hit on each tower to be recorded. It's certainly true that data size can increase by as much as a factor of 20 for single high energy photons (100 GeV), but in the 'bread and butter' region (2-10 GeV) the photon penalty ranged from 3-6. For neutrons, the penalty ranged from 1.2 to 2.5 across the energy range 1 GeV to 100 GeV. This is not trivial, but then again, everyone keeps telling me how cheap disk is these days... It may be too late to do this with our Gismo studies, but if we migrate to Geant 4 and have to rewrite our hit/digitization routines, this is certainly worth considering. Taking this logic to its natural conclusion then the current round of modifications to the S&L detectors (sounds like a bailout waiting to happen!) should concentrate on the distribution of MASS in those detectors. The truly expensive part of full simulation is transporting particles through matter and any redistribution of matter forces another round of transportation. If we get the mass distribution right and we record only -exact- hits at reference planes, then studies like segmentation of the calorimeters or point resolution of tracking devices become (computationally) trivial (which is probably why the tracking guys have been doing this all along!) My apologies to experienced simulators out there to whom I have just stated the obvious. Tony Waite.