These plots were made from 5000 each of mu, pi-, and gamma single-particle events with eta distribution from -.2 to 1.2 and pt distribution from 5 to 40 GeV.  Tower clustering was done using a 1 GeV threshold for seed towers and a 4 GeV threshold for 2x2 clusters for all particle species.  Then for each cluster, the four preshowers in front of that cluster were identified and a preshower cluster energy and energy-weighted eta calculated using the geant energy deposition in the preshower.  Below are shown various plots of preshower energy (in Figures 1-3) (Note that the middle right plot is broken: however, this plot is also available in the previous blog post).  In the log preshower energy (in MeV0 vs. log tower energy (in GeV) plot, gammas and piminus were well separated and a cut was imposed discarding all hits with log preshower energy and log tower energy both less than 1 (i.e., the hit has less than 10 GeV of tower energy and less than 10 MeV or preshower energy).  As can be seen in Figures 4-6, this cut removes very few photons between a quarter and a third of the piminuses (muons are mostly eliminated in the initial clustering stage).

Figure 1: Muon Preshower Plots

Figure 2: Gamma Preshower Plots

Figure 3: Piminus Preshower Plots

Figure 4: Mu Cut Results

Figure 5: Gamma Cut Results

Figure 6: Piminus Cut Results