1. By: Daniel Coelho Matthew Szydagis Robert Svoboda Improving Electron / Gamma Separation LBNE Software Fermilab, ILFebruary 1, 2013

2. 2/9LBNE e- / gamma Seperation 02/01/14 Introduction Cross-check of LArSoft with an independent, standalone Geant4 simulation that includes NEST (BACCARAT – See talk by Vic) Simplistic geometry, just a large vat of liquid argon, all that was needed NEST ensures realistic Q as a function of dE/dx, vetted against ICARUS data Including noise this time, and averaging over all possible track angles Goals of this work Improve methods of e/gamma separation Continuing the addition of more accurate affects of the background. Understand causes of gamma contamination (and try to eliminate them) Looking only at 0.5 GeV electrons and 0.5 GeV gammas this time (10,000 of each were simulated) Crossover point between e-, gamma populations used to determine electron acceptance and gamma contamination

3. 3/9LBNE e- / gamma Seperation 02/01/14 Definitions Acceptance is defined as the number of electron events accepted by virtue of being to the left of a cut on the total charge collected, divided by the total number of electron events simulated. It is also called Purity. Contamination is defined as the number of gamma events which crept in to the left of that cut divided by the total number of events (of either type) which make the cut. It is also known as the Leakage.

4. 4/9LBNE e- / gamma Seperation 02/01/14 Example Histograms Wire pitch of 5 mm Track length of 2.1 cm Acceptance = 90% Contamination = 10% The fits shown help determine the dividing line, removing the possibility of a poor dividing line due to small fluctuations Electrons Gammas

5. 5/9LBNE e- / gamma Seperation 02/01/14 Expanding on Wire Model The initial results at shown at fort Collins uses a wire model of counting thermal electrons that are a certain distance from a wire. Original study was 1 dimensional in nature, however it did compensate for the differing gamma directions in the detector by averaging over the angles. To add accuracy the model was expanded in three dimensions in order to account for the separate wire planes U, V, and collection. Track Resolution also added to model uncertainty in the reconstructed track length

6. 6/9LBNE e- / gamma Seperation 02/01/14 Charge Interpolation In order to improve accuracy in the e- gamma separation using spline fitting of the charge yield histogram was suggested since it removes the dependency on using the cross over point of the two histograms. The results are slightly worse compared to previous studies, but achieve greater linearity in the performance plots. Using the best fits themselves as a means of calculating the signal and background acceptances were attempted in conjunction of using the MC histograms. The performance of the fits appear to give better results at smaller track lengths. Track Segment 10 mm 11 mm 12 mm 13 mm 14 mm 15 mm 16 mm 17 mm 18 mm 19 mm 20mm 21 mm 22 mm 23 mm 24 mm 25 mm 26 mm 27 mm 28 mm 29 mm 30 mm 31 mm 32 mm 33 mm 34 mm 35 mm 36 mm 37 MM 38 mm 39 mm 40 mm 41 mm 42 mm 43 mm 44 mm 45mm

7. 7/9LBNE e- / gamma Seperation 02/01/14 Quick look at 36 vs 45 UV config. As given in some previous plots there is not a huge difference between the two configurations with a slight advantage to the 36 configuration. The difference is about.1% at optimum track length for both signal and background. Higher track lengths segments seem to have better performance with 36 than 45.

8. 8/9LBNE e- / gamma Seperation 02/01/14 A technique attempted was to weigh the beginning of the track where dE / dx is most important over other parts of the track which was weighted less. A general exponential was used with a time constant based upon track length. Optimization of this method showed the time constant tended to 0 meaning the exponential did not end up helping. Maybe there is another clever way to do this using another function or weighting scheme? Maybe a contextual track weighting by looking at the track. Weighting the Charge

9. 9/9LBNE e- / gamma Seperation 02/01/14 Current and Planned Tasks In Progress Different energy results are almost ready, unfortunately simulations were not able to finish before the talk. :( Work will continue and will be done by the end of the current collaboration meeting! Analysis of initial hadronic shower (caused by proton from charge current interaction) is still to be modeled but is still actively being pursued. (GENIE) Future Work Modeling radioactive and cosmic ray backgrounds Implementing advanced event rejection Using Neural Networks / Boosted decision tress / Pandora