Development of New SPR-based Kaon, Pion, Proton, and Electron Selectors

1. Development of New SPR-based Kaon, Pion, Proton, and Electron Selectors Kalanand Mishra University of Cincinnati

2. Why New Selectors ? • For B-tagging, need new Kaon selector to replace the old KNN selectors. • - The KNN selectors haven’t been trained since circa 2001; there have been • many changes in the detector performance since then (e.g., Track Fix up, • Sasha Telnov’s corrections for dE/dx in DCH and SVT). • - Trained on Monte Carlo, but are used to evaluate performance in real data. • - Give degraded performance for high-momentum tracks. • - Need a general-purpose high-performance Kaon selector for Physics analysis. • For protons and pions, there is only one selector of choice for analysis: the Likelihood selectors. There is room for improvement in the performance. • For electron, the selector of choice at the moment is again the LH selector. • - It provides electron selection at only one level of strictness. • - Analysts have been asking for both looser and tighter level selections. • - Also some analyses and AWGs (notably Leptonic) will benefit enormously • from high-performance selectors for both low and high momentum tracks. • - The improvement in performance of this selector will be very important for • crucial BaBar analyses looking for New Physics, rare decays, CP violation ….

3. What is New in the New Selectors ? • Training on “real data”. • Include Sasha’s corrections for dE/dx in DCH and SVT. • Employ powerful statistical tools to separate signal and background, use boosting on weak classifier and multi-class training. • For each class of particle hypothesis: “kaon”, “pion”, “proton”, and “electron”, the other three classes are treated as background for classifier training. The only veto we need to apply is “muon veto” for ‘tight’ and ‘very tight’ selections. No additional vetoes. • Include many additional useful input variables, including P and  after flattening the two-dimensional P:  distribution. No need for separate trainings in P, bins.

4. Tried Various Classification Algorithms ... Binary Ada Boost Simple Binary Split Fisher Bkgd. Sgnl. Ada Boost Decision Tree Bagger Decision Tree Events ( Provides the best separation ) Classifier Output

5. StatPatternRecognition : AdaBoost For details on the algorithms and software used, see: arXiv:physics/0507143 (by Ilya Narsky) For illustration only Events • Decision Tree splits nodes recursively until a stopping criteria is satisfied. • AdaBoost combines weak classifiers by applying them sequentially. At each step it enhances weights of misclassified events and reduces weights of correctly classified events. Sgnl. Bkgd. Classifier Output

6. Performance of Kaon selector Includes all momentum and  ranges and all tracks. The higher curve/ point represents better performance

7. Kaon Performance in select mom. bins Low momentum: 0.3 < P < 0.5 GeV/c dE/dx - DRC transition: 0.8 < P < 1 GeV/c High momentum: 3.0 < P < 3.2 GeV/c Intermediate range: 1.9 < P < 2.1 GeV/c

8. Kaon Performance by Track Quality Tracks passing through cracks between the DIRC bars Tracks in DIRC Caveat: The separation between the two categories is a bit fuzzy in my code ! Conclusion: Improvement in performance everywhere. Tracks passing through cracks between the DIRC bars: P > 1 GeV/c

9. Performance of Kaon selector LH Loose: Efficiency = 0.87 Pi Rej. = 0.96 LH Tight / VeryTight: Efficiency = 0.82 Pi Rej. = 0.98  LH V.Loose Caveat: These numbers are very crude approximations !

10. Performance of Pion selector LH Tight / Very Tight  Caveat: The numbers for LH selectors are very crude approximations !  LH Loose

11. Performance of Proton selector Looks good. But Need to see performance for the entire P,  spectrum.

12. Performance of Electron selector Looks good…. But again need to see performance for the entire P,  spectrum.

13. Status of the New Selectors in BetaPid • A new selector class implemented in my private version of BetaPid. • I am in the process of finalizing the cuts for levels of strictness: “extra loose”, “very loose”, “loose”, “tight”, “very tight”, “extra tight”. For electrons, there will be four or less levels. • Will do some additional tests for validation and will commit the code afterwards (expect 1-2 weeks). • The PID group will do the ultimate validation (expect few more weeks). • After getting OK from the PID group, the new selectors will be ready for deployment hopefully by the end of August.