Crosstalk Removal to
Improve Muon dE/dX
Measurements
Leo Jenner, UCL
2 Oct 2003
UCL 2nd Year Talk
1
In brief
Crosstalk removal
algorithm
Comparison of
Tracking +
Crosstalking to MC
truth
Some hitches…
Preliminary
comparison of MC to
data
2 Oct 2003
UCL 2nd Year Talk
2
A Cosmic Ray Muon
Crosstalk removal helps with Tracking and is
also important for correcting muon dE/dX for
relative calibration of the MINOS detectors.
2 Oct 2003
UCL 2nd Year Talk
3
CrossTalk Algorithm
Work through all the hits in a given pair of
planes and look at the 8 pixel window
around each ‘test’ hit
Sum the charge and identify the largest hit
in the window
The test hit is flagged as crosstalk if its
charge is less than the sum of the pixels
around it, multiplied by a user definable
factor. This is usually set to 1 for
beam/cosmic muons since low energy
deposition combined with photon statistics
can lead to crosstalk with very comparable
energy to real hits
The Crosstalker currently runs as a module before the CalDet muon tracking code
Testing is taking place on Crosstalking Monte Carlo
2 Oct 2003
UCL 2nd Year Talk
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Number of Crosstalk hits: Truth vs Tracked
The crosstalker finds about 82% of the crosstalk
hits as I’ve opted for a high purity (>90%)
2 Oct 2003
UCL 2nd Year Talk
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dE/dX from Monte Carlo (Truth and Tracked)
2 Oct 2003
UCL 2nd Year Talk
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Comparison of MC truth to MC+Tracking
For the most part there is good agreement…
2 Oct 2003
UCL 2nd Year Talk
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Number of Hits: Tracked/Truth
•A close up of the last
few planes shows the
discrepancy increasing
But only 0.32% of
events go to plane 54
or more…
2 Oct 2003
UCL 2nd Year Talk
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Last Plane Hit
Some of the hits at the end of the track seem to go
missing after tracking…
2 Oct 2003
UCL 2nd Year Talk
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Very curvy muons
In the third plot along the two blue hits at the end of the track are genuine track hits
Maybe the muon curves sharply to the left and travels in the air gap between planes
The tracker doesn’t nominally find the last hit because it falls outside of the search
window
Noise also creates spurious hits at the end of the track
2 Oct 2003
UCL 2nd Year Talk
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Preliminary comparison to data
Quite low statistics but it still looks a bit odd
2 Oct 2003
UCL 2nd Year Talk
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Data - Last Plane Hit
Even with cut: 10<first
strip hit <13
‘PS’ Muons,
Other off
momentum
muons coming
down the
beampipe
2 Oct 2003
UCL 2nd Year Talk
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Conclusion
More work to do to optimise Tracking and
Crosstalk removal using Monte Carlo
Fold crosstalk back into real hits to further
improve MC dE/dX
Apply crosstalk removal to data
2 Oct 2003
UCL 2nd Year Talk
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2 Oct 2003
UCL 2nd Year Talk
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Anomalies
Entry: 2340943 Record: 3107 End: A Plane: 48
Strip: 8 HitBit: 786432 PE: 5.86536 TrackEnd: B
Plane: 48 Strip: 8 HitBit: 786432 PE: 7.3501
Entry: 2340944 Record: 3107 eventnum: 3107
Entry: 2340945 Record: 3107 eventnum: 3107 :
End: B Plane: 54 Strip: 10 HitBit: 0 PE:
0.935773
2 Oct 2003
Entry: 2340946 Record: 3107 eventnum: 3107
There is an unphysical hit of nearly
1pe… it’s ignored by the truth (see
above) but the tracker finds it
UCL 2nd Year Talk
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Number of Hits Truth vs Tracked
Plane No. MC Tracked MC Truth Ratio
Comment
19
9802
9868
1.007 Typical Plane
48
6163
6267
1.017 Lph mean here
49
4208
4332
1.03
50
2267
2357
1.04
51
881
931
1.058
52
236
289
1.22
53
73
104
1.42
54
23
40
1.74
55
6
25
4.15
56
3
24
8
57
0
12
58
0
12
59
0
6
60
0
6
2 Oct 2003
UCL 2nd Year Talk
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