Documents to Review

Tentative Agenda

Blake looked at his bggen folders to find that a BGGEN hddm file is ~1kB/event (10^7 events is ~10GB) and an HDGEANT hddm file (from filtered BGGEN events) is ~27kB/event. Filtering the data for neutral energy greater than 6GeV culled 80% of events. The final data set is after runnning though HDGEANT ~55GB for 2x10^6 events therefore an unfiltered set of 10^7 events would have a data storage size of 275GB.
Reconstruction

It is required that there are 4 or 5(~5% of accepted events) photons showers (none are due to charged particles - comparing swum tracks to shower positions), and 1 proton. This gives 6(30) possible combinations.
Pi0 and Eta candidates are chosen as the eta-pi0 pair with the largest probability (from the TwoGammaFit )
Before χ^2 cuts ~50% of the generated signal events can be reconstructed. A cut on χ^2 < 3 leaves approximately 39% of generated events,
10^7 Pythia hadronic background events were generated and then filtered by requiring that the total neutral energy be greater than 6GeV. 50,000 signal a2(1318) events were generated. This gives a ratio of cross-sections being 200:1 where the Pythia cross section at 9 GeV is 124 μb giving a cross section for the a2 to be ~0.6 μb. The 4 photon, 1 proton requirement leaves 12,690 background events and 24,870 signal events (5% more including 5 photon events).
Protons (acceptance and smearing) are handle via HDParSim, a parametric Monte Carlo used as a plugin with the analysis code

π0 mass: the lines in black are Pythia + signal events, red are cutting on χ^2 < 3, green is Pythia background only cut on χ^2 < 3.