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

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
S. Durkin, CSC DPG, Jan. 25, 2007

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?
S. Durkin, CSC DPG, Jan. 25, 2007

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
Layers Hit
# Segments
(measured)
(theory) 6
17105 5
4161 4
1318
421 3
444 23
Layers Hit
# Segments
(measured)
(theory) 6
11236 5
4850 4
2886
872 3
1791
983
Poor Agreement due to extra tracks with N not equal 6
S. Durkin, CSC DPG, Jan. 25, 2007

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
S. Durkin, CSC DPG, Jan. 25, 2007

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!
S. Durkin, CSC DPG, Jan. 25, 2007

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 !
S. Durkin, CSC DPG, Jan. 25, 2007

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.
S. Durkin, CSC DPG, Jan. 25, 2007