When we start looking for pi0's in the AuAu data, we'll probably need to use pre/postshower information where we have it to cut down on backgrounds. Here are some preliminary results. I've developed a set of cuts, just to get a feel for how to use the pre- and postshower information.
Energies are summed over all towers in a given cluster. The y-axis shows energy deposited in the specified pre/postshower layers. The x-axis shows the total reconstructed energy of the cluster (despite the "tower" label.)
At 5 GeV, 36% of electrons can be rejected using preshower layers, by rejecting events if 0.8 < E(1) < 1.4 MeV AND E(2) > 0.8 MeV. This rejects 23% of pi0's at 5 GeV. Making the preshower-2 cut a function of preshwer-1 may improve pi0 retention...
Here I've plotted the ratio of preshower (postshower) energy deposit to reconstructed tower energy. Probably don't need to take ratios here. Anyway, based on the "bananna" cuts shown by the red bands in preshower-1 and preshower-2, plus a (reasonable) postshower cut, one can reject 70% of 5 GeV h+, 76% of 10 GeV h+ and 81% of 15 GeV h+ just using pre/postshower information. This is in addition to the much-reduced cluster-finder efficiency for charged hadrons which often do not deposit enough energy for the cluster finder to identify it as a cluster. 75% of 5 GeV pi0's are retained using my "straw man" cuts.
