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Studies of Segment Reconstruction Where did the RecHits go ?

Studies of Segment Reconstruction Where did the RecHits go ?. S. Durkin The Ohio State University CSC Detector Performance Group Jan. 25, 2007. A Residual Mystery. Residuals Better on Outer Planes!. Simple MC of 3D Hit Shows this is Impossible. Gain on Outer Layers Typically 20% Higher

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Studies of Segment Reconstruction Where did the RecHits go ?

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  1. Studies of Segment Reconstruction Where did the RecHits go ? S. Durkin The Ohio State University CSC Detector Performance Group Jan. 25, 2007

  2. A Residual Mystery Residuals Better on Outer Planes! Simple MC of 3D Hit Shows this is Impossible Gain on Outer Layers Typically 20% Higher Is this a Segment Finder Bias ?

  3. SK Segment Finder Problem Kalman Filter Schematic Chi-Square Cut as Implimented does not work properly Choose 2 Seed RecHits layer diff – WideSeg local x – dRPhiMax local  - dPhiMax Typical Segment 2= 729/4 d.o.f. Add RecHit Candidate (cut on segment residuals) local x – dRPhiMax local  - dPhiMax with chisqrMax=60/d.o.f. cut Reject Fit 3D Line All RecHits chisqrMax = 60/D.O.F. 2= 16/5 d.o.f. Accept Accept RecHit no chisqrMax cut

  4. SK Segment Finder Problem (cont.) Clear delta ray. Huge Charge, 2 anode wire groups How Algorithm Fails Chi-Square Cut removes good hits leaving bad hits. Wrong line segment is found! • Local x and Global  roads well optimized • Chi-Square Cut should be done later • - removal of delta rays • Local x and Global  same road • Why are there no roads in Local y?

  5. SK Segment Finder Problem (cont.) • The Chi-Square Cut has a big effect numerically • MTCC data set very messy! Showers, Spray,… • Have seen 6 segments in a given chamber Naïve Model: e – efficiency N6=e6 N5=6 e5(1-e) N4=15 e4(1-e)2 … Calculate e from N6 and N5. No ChisqrMax Cut e=0.96 ChisqrMax=60 Cut e=0.93 Poor Agreement due to extra tracks with N not equal 6

  6. TMB Trigger Bias Explanation Segments with 5 hits miss layers 1&6 more often Excess about 7% of all Segments Missing Layers Position of Missing RecHits Layers 2,3,4,5 Layers 1,2

  7. TMB Trigger Bias Explanation (cont.) • TMB Cathode Trigger is designed to be seamless • Seamless design will be implimented by Spring • MTCC running an overlap between CFEBs existed (Hauser) • TMB LCTL1A send 5 signals to CFEB indicating CFEBs to read • Ideally if triggered track inside one CFEB then 1 CFEB is read • Ideally if triggered track crosses boundary between CFEBs then 2 CFEBs Read •••••• Can be missing in MTCC data • • • • • • MTCC Trigger sometimes doesn’t read out second CFEB!

  8. RecHitB Efficiency Problems • Gatti Fits performed on RecHits with missing CFEB charges Fixed • RecHits with Central Charge Peak in 3rd Time bin removed Fixed • ran on MTCC Run 4413 • Apparently timing not tuned perfectly • Remove about 20% of RecHits • No Correlated Noise Matrix for Bin 3 • More of a timing problem but fix it anyway Warning to RecHitB Users: By default RecHitB does hidden 2D wire and strip segment finding ! untracked bool CSCuseCleanWireCollection = true; untracked bool CSCuseCleanStripCollection = true; RecHits not on 2D segments are removed !

  9. Back to Slide One Mystery • We should not be calling multiple segment finders. • This is definitely inefficient. • It the 2D finders work so well, then we should just use them Misha confirms the Landau’s in Planes 1 & 6 are Higher ! Nobody seems to understand this.

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