The following image shows the shower profile of a Bhabha electron; the horizontal axis shows the depth within in the calorimeter, numbered by detector layer and the vertical axis shows the radial coordinate in units of pads. The colors are proportional to the energy deposited in pad.
The following plot shows the correlation of the energy (shown as the fraction of the energy of the beam) of the calorimeter on one end of OPAL with the calorimeter on the other end for events that had sufficient energy to provide a SW trigger. All acceptance cuts have been applied except for the energy cut, which is shown graphically.
The Bhabha peak is clearly separated from the off-momentum background.
Information about the silicon tungsten calorimeter
The construction of the SW calorimeter