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Kalman Fit For PHENIX Central Arms

Kalman Fit For PHENIX Central Arms. Evolution of Fit Formalism What is the Kalman Fit? New formalism for non-linear measurement matrix Results for Run-3 dAu Mass 2 resolution for p/pbar Simulation results for Run-4 configuration Improved momentum resolution at high p T Application to SVX

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Kalman Fit For PHENIX Central Arms

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  1. Kalman Fit For PHENIX Central Arms • Evolution of Fit Formalism • What is the Kalman Fit? • New formalism for non-linear measurement matrix • Results for Run-3 dAu • Mass2 resolution for p/pbar • Simulation results for Run-4 configuration • Improved momentum resolution at high pT • Application to SVX • Measurement of displaced vertices J. Lajoie - Kalman Fit for PHENIX

  2. The Kalman Filter • General Introduction • …goes here J. Lajoie - Kalman Fit for PHENIX

  3. What can we hope for? Very old MC study – assumed 150um TEC resolution and observed poor momentum for standard reconstruction. Not much Improvement below 5 GeV/c, ~x3 improvement at 20GeV/c. Just adding PC’s gives modest improvement (west arm). J. Lajoie - Kalman Fit for PHENIX

  4. Application to Run-3 dAu • Run 69502 • dAu chosen as a start to avoid hit association issues • On everybody’s “good run” list • Good TEC efficiency in sectors 2,3 (TOF) • Reconstructed and fit 190 file segments • Kalman uses DC X, UV hits, PC1, and TEC • UV hits fit only in z, filtered at 2.5 sigma • Magnetic field scaled up by 1.7% • Examine fit systematics… J. Lajoie - Kalman Fit for PHENIX

  5. Time to Run Kalman Filter J. Lajoie - Kalman Fit for PHENIX

  6. Chi-Square Distributions Not a true chi-square per d.o.f – just the total chi-square divided by the of contributing detector hits. J. Lajoie - Kalman Fit for PHENIX

  7. TEC “residuals” Look at TEC residuals for sectors 2,3 (TOF coverage) for “in” point (TEC “out” point is similar) Red: before Kalman Fit Blue: after Kalman Fit Number of tracks Number of tracks Dj (radians) Dj (radians) The track is “pulled” to the TEC hits by the fit. J. Lajoie - Kalman Fit for PHENIX

  8. Run 3 dAu – p/pbar mass2 Good DC tracks, with associated TOF, PC3 hits and TEC track. pT>2.0 GeV/c Kalman Fit (DC+PC1+TEC) Standard PHENIX Number of tracks Very small effect (if any), but at “low” pT. J. Lajoie - Kalman Fit for PHENIX

  9. Momentum Distribution Momentum distribution for all tracks with associated TEC track: Red: before Kalman Fit Blue: after Kalman Fit Number of tracks pT (GeV/c) Softer slope for distribution after Kalman fit, consistent with improved resolution. J. Lajoie - Kalman Fit for PHENIX

  10. Run-4 Simulation Results • Larger magnetic field (++ configuration) • More bend, better resolution • Kalman won’t help as much until higher pT • Single pion events in pisa • No decays, hadronic interactions • Examine ptot=2,5,10 and 20 GeV/c • East Arm: • Fit DC+PC1+TEC • West Arm • Fit DC+PC1+PC2+PC3 • Can Kalman help in Run-4? J. Lajoie - Kalman Fit for PHENIX

  11. Example: 20 GeV/c p+ (East Arm) Kalman CGL Almost a factor of two improvement in resolution! Number of tracks p (GeV/c) p (GeV/c) J. Lajoie - Kalman Fit for PHENIX

  12. Example: 20 GeV/c p+ (West Arm) Kalman CGL If anything the resolution got a little worse! Number of tracks p (GeV/c) p (GeV/c) J. Lajoie - Kalman Fit for PHENIX

  13. What’s going on in the West? • No resolution improvement with DC+PC1/2/3 • Resolution worsens a little (!) • Probably due to Kalman errors not tuned to MC • Assuming errors too small builds in fluctuations • Consistent with PC phi error being larger than “projection” error • Little information added from additional hits • No help for Run-4! J. Lajoie - Kalman Fit for PHENIX

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