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Status of Pattern Recognition for the T-Tracker Hans Wenzel, Hogan Nguyen March 12 th , 2011

Status of Pattern Recognition for the T-Tracker Hans Wenzel, Hogan Nguyen March 12 th , 2011. Introduction Hans implemented stereo hits, formed by the intersection of 2 clusters within a plane (0-35)

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Status of Pattern Recognition for the T-Tracker Hans Wenzel, Hogan Nguyen March 12 th , 2011

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  1. Status of Pattern Recognition for the T-Tracker Hans Wenzel, Hogan Nguyen March 12th, 2011 Introduction Hans implemented stereo hits, formed by the intersection of 2 clusters within a plane (0-35) Basic Pattern Recognition Concept: Start with a2D Circle Fitter, using these stereo hits. We analyze here how well this works. Note: We view this 2D fitter as part of the Pattern Recognition Algorithm, whose goal is to handing off good straw hits to the Kalman Fitter.

  2. Outline - Quick Review Of Basic Concepts and Previous Work (http://mu2e-docdb.fnal.gov:8080/cgi-bin/ShowDocument?docid=1337) - Z information from the 2D Fitter - Evaluation of simple pattern recognition with Accidental Overlays - New Tools to Help Pattern Recognition (Hans)

  3. 6 Configurations for Stereo Hits Panels Used Plane ----------------------------------------------- 0 & 1 or 3 & 4 even plane 1 & 2 or 4 & 5 even plane 2 & 3 or 5 & 0 even plane 0 & 1 or 3 & 4 odd plane 1 & 2 or 4 & 5 odd plane 2 & 3 or 5 & 0 odd plane

  4. electron Systematic Shift of Stereo Hit Position straw cluster Example: polar angle = 72 degrees Phi angle = 90 degrees No Shift in Y coordinate. Systematic shift in X coordinate = (19/2 mm)/tan(90-polar)*tan(30) = 17 mm true position Stereo Hit Position straw cluster systematic shift in position

  5. Fit Minimizes Perpendicular Distance To Circle. 3 free parameters for a 2D circle: X0, Y0 is the fitted center, and R is the fitted Radius Notes NO SEARCH ALGORITHM – ALL Stereo Hits are used in the FIT Errors Calibrated From MC (see Next Slide) Adhoc Correction done to account for polar angle dependence of the Stereo Hit. Can do it rigorously later

  6. Errors Used in the 2D Fit. Calibrate using Monte Carlo Radius of Stereo Hit - Radius of True Hit Phi – True Phi Configuration number Radius Error of 2 mm Phi Error of 5 degrees (Phi not used in the fit)

  7. Fit Consistency Low Probability Fits due to Multiple Scattering, Interactions, and Pathological Cluster Shapes allow 1 iteration to refit excluding the worse chi2 contributor Rejecting Low Probability Events Keeps = 83% (NO OTHER HITS)

  8. Z information from the 2D fitter Definition Delta phi = angle of stereo hit with respect to first stereo hit Period in Z = Position drift in Z for ONE complete orbit rotation. Calculated ASSUMING p=105 MeV Hypothesis Z Period number (dimensionless) = Number of Z periods third hit second hit first hit

  9. Ideal Case All Hits from Conversion Events Lie on the Curve, Independent of Polar Angle of Conversion Electron Delta Phi Z Period Number (calculated assuming Conversion Electron Hypothesis)

  10. Monte Carlo Truth Positions Used & Selected P > 103 MeV Rotation Angle (Phi) versus Z Delta Phi (degrees) 2000 generated conversion events Z period Number (dimensionless) Radiated Conversion Electrons cause off-diagonal points

  11. Rotation Angle (Phi) versus Z Reconstructed Stereo Hits Used Delta Phi (degrees) 2000 generated conversion events Errors in defining the First Hit (1% effect) Z period Number (dimensionless)

  12. Overlay of Accidental Hits onto Conversion Events Process Rate Per Microbunch Number of Clusters Pure Conversion -- 23 Ejected Protons 5628 16 (After ADC cut) Decay In Orbit* 36K 4 Pion Capture 75 7 Cosmics small ~ 0 Electronics Noise Study Not Done TBD * Generated only DIO with E>60 MeV to save computing time Thanks to: Gianni, Bob, Craig for Rates

  13. 100 Pure Conversion Electron Events ( cos(polar) = 0.3) Fit Cut Eff = 83% delta Phi Stereo Hits in Circle-Centered Coordinates Z Period Number

  14. 100 Conversion Electron Events Overlayed with Pion Capture Fit Cut Eff = 66 % Pion Capture Adds ~ 7 Clusters Per Event delta Phi Stereo Hits in Circle-Centered Coordinates Z Period Number

  15. 100 Conversion Electron Events Overlayed with DIO Events Fit Cut Eff =70 % DIO Adds about 4 Clusters Per Event delta Phi Stereo Hits in Circle-Centered Coordinates Z Period Number

  16. ADC is Critical for Removing Proton Ejection Events Proton Ejection Events Conversion Events ADC < 6 KeV

  17. 100 Conversion Electron Events Overlayed with Proton Ejection Events Fit Cut Eff = 10 % Proton Ejection Events add 16 more clusters per event (after ADC cut) Stereo Hits in Circle-Centered Coordinates Z Period Number

  18. What Next - The ADC cut is critical. It is doing the lion’s share of removing bad hits. - Simple 2D fitter with NO search algorithm fails with accidentals - Need to Beef up the 2D fitter with a search algorithm - Hans will discuss other tools.

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