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Analysis of the Stereo Hits and the 2D Circle Fitter Hans Wenzel, Hogan Nguyen Feb 9 th, 2011 Introduction Hans implemented stereo hits, formed by the intersection of 2 clusters within a plane (0-35) A 2D Circle Fitter, using these stereo hits have been implemented in ReadStrawCluster_plugin.cc We analyze here how well this works. For simplicity, we initially remove the straw wall and wire material, to study the fit behavior with less material. 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

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6 Configurations for Stereo Hits Panels Used Plane & 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 2

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3 Example: Configuration = 1 Even plane, panels 0 and sector 1 Banana Shape Described by polar angle. Location in Banana given by “Phi” angle. Note the offset from Origin. For now, use adhoc correction to shift banana to go through origin. Can do rigorously later. Offset from Origin of Order 5 mm. Difference between reconstructed position and Actual Position Sanity Check: polar angle = 72 degrees Maximum shift = (19/2 mm)/tan(90- polar)*tan(30) = 17 mm

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Comparing Reconstructed Stereo Hit Position with True Hit Position (in millimeters) ~4 mm Gaussian sigma Correlation depending on “Configuration of Stereo Hit” even planes odd planes cos(polar)=0.3 4

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Stereo Hit Resolution Dependence on the 6 Configurations cos(polar)=0.3 5

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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 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

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Radius of Stereo Hit - Radius of True Hit (millimeters) Configuration number sigma = 2.0 mm for all configurations Errors Used in the 2D Fit. Calibrate using Monte Carlo cos(polar)=0.3 7

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Fit Consistency allow 1 iteration to refit excluding the worse chi2 contributor Straw wall and wire REMOVED from G4 simulation cos(polar)=0.3 8

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allow 1 iteration to refit excluding the worse chi2 contributor Straw wall and wire INCLUDED in the G4 simulation Fit Consistency More material increases the Number of Low Probability Fits 9

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Requirement Efficiency 0 No Cuts 1 >= 15 straw hits 2 >= 20 straw hits 3 >= 25 straw hits 4 >= 6 clusters 5 >= 4 stereo hits 6 fit probability > 1% 69% Cos(polar) = 0.3 Cut Number 10

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cos(polar)=0.5 32% eff cos(polar)=0.7 1% eff (big drop in requiring 4 stereo hits)(big drop in requiring 15 hits) Cut Number 11

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12 Ongoing Code Development persistent StrawCluster/StrawClusterCollection before: was Vector of StrawID's: typedef std::vector StrawCluster; typedef std::vector StrawClusterCollection; now persistent pointer to StrawHits auto_ptr listofptrtoHits(new DPIndexVectorCollection); DPIndexVector ptrtoHits; All code (new/old) resides in CVS: make the Clusters: HitMakers/src/MakeDPIStrawCluster_plugin.cc access and analyze the Clusters: HitMakers/src/ReadDPIStrawCluster_plugin.cc run it: HitMakers/test/makeDPIStrawClusters.py (makes StrawHits-> Clusters --> analyzes ) working on: r-z fit, comparing found hits with hits associated to conversion electron (ConvElecUtilities), proper classes to output --> input to final fitter.

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Back up 13

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Fit Consistency, when using ACTUAL Track position in the Fit. Straw Wall and Wire Removed from G4 Simulation 14

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