1. 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) Basic Pattern Recognition Concept: Start with a 2D 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. 1

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 3

4. 4 systematic shift in position straw cluster straw cluster electron 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 Systematic Shift of Stereo Hit Position Stereo Hit 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 5

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

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

8. 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 first hit second hit third hit DefinitionZ information from the 2D fitter

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

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

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

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) delta Phi Z Period NumberStereo Hits in Circle-Centered Coordinates Fit Cut Eff = 83%

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

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

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

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