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. ID: 576045
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Analysis of the Stereo Hits and the 2D Circle Fitter Hans Wenzel, Hogan NguyenFeb 9th, 2011
IntroductionHans implemented stereo hits, formed by the intersection of 2 clusters withina plane (0-35)A 2D Circle Fitter, using these stereo hits have been implemented inReadStrawCluster_plugin.ccWe analyze here how well this works.For simplicity, we initially remove the straw wall and wire material, to study the fitbehavior with less material.Note: We view this 2D fitter as part of the Pattern Recognition Algorithm, whose goalis to handing off good straw hits to the Kalman Fitter.
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
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 togo through origin. Can do rigorously later. Offset from Origin of Order 5 mm.
Difference between reconstructed position and Actual Position
Check: polar angle = 72 degrees
Maximum shift = (19/2 mm)/tan(90-polar)*tan(30
) = 17 mmSlide4
Comparing Reconstructed Stereo Hit Position with True Hit Position (in millimeters)
~4 mm Gaussian
Correlationdepending on“Configuration of Stereo Hit”
Stereo Hit Resolution Dependence on the 6 Configurations
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
Errors Calibrated From MC
(see Next Slide)Adhoc Correction done toaccount for polar angle dependence of the StereoHit.Can do it rigorously later
Radius of Stereo Hit - Radius of True Hit (millimeters)
sigma = 2.0 mmfor all configurations
Errors Used in the 2D Fit. Calibrate using Monte Carlo
allow 1 iteration to
refit excluding theworse chi2 contributorStraw wall and wireREMOVED from G4 simulation
allow 1 iteration to
refit excluding theworse chi2 contributorStraw wall and wireINCLUDED in the G4 simulation
More materialincreases the Number of Low ProbabilityFits
0 No Cuts1 >= 15 straw hits2 >= 20 straw hits3 >= 25 straw hits4 >= 6 clusters5 >= 4 stereo hits6 fit probability > 1% 69%
Cos(polar) = 0.3
(big drop in requiring 4 stereo hits)
(big drop in requiring 15 hits)
Ongoing Code Development
persistent StrawCluster/StrawClusterCollection before:was Vector of StrawID's:typedef std::vector<mu2e::StrawId> StrawCluster;typedef std::vector<mu2e::StrawCluster> StrawClusterCollection;now persistent pointer to StrawHitsauto_ptr<DPIndexVectorCollection> listofptrtoHits(new DPIndexVectorCollection);DPIndexVector ptrtoHits;All code (new/old) resides in CVS:make the Clusters:HitMakers/src/MakeDPIStrawCluster_plugin.ccaccess and analyze the Clusters:HitMakers/src/ReadDPIStrawCluster_plugin.ccrun it:HitMakers/test/makeDPIStrawClusters.py(makes StrawHits-> Clusters --> analyzes )
fit, comparing found hits with hits associated
classes to output --> input to final fitter.Slide13
Fit Consistency, when using ACTUAL Track position in the Fit.
Straw Wall and
Wire Removed from G4 Simulation