silicon tracking for forward electron identification at cdf david stuart, uc santa barbara oct 30,...
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![Page 1: Silicon Tracking for Forward Electron Identification at CDF David Stuart, UC Santa Barbara Oct 30, 2002 David Stuart, UC Santa Barbara Oct 30, 2002](https://reader030.vdocuments.net/reader030/viewer/2022033106/56649d625503460f94a45092/html5/thumbnails/1.jpg)
Silicon Tracking for ForwardElectron Identification
at CDF
Silicon Tracking for ForwardElectron Identification
at CDFDavid Stuart,
UC Santa BarbaraOct 30, 2002
David Stuart,UC Santa Barbara
Oct 30, 2002
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OutlineOutline
•Motivation and HistoryMotivation and History
•CDF Run II upgradeCDF Run II upgrade
•Forward Tracking algorithmForward Tracking algorithm
•Physics ProspectsPhysics Prospects
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In Run 1, CDF had tracking only in central region
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Physics beyond ||=1 e.g., look at of e in Z e+e-
||<1 =50%
||<2 = 83%
…but what mattersis finding both
e+ and e-…
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What is of max e in Z e+e-
||<1 =25%
||<2 = 70%
ET > 20 GeV
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More central at high mass, e.g. 800 GeV/c2 Z e+e-
||<1 =53%
||<2 = 90%
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Some plug e ID
•Had/EM < 0.05
•Isolation < 0.1
•VTX Occupancy
Plug Electron ID in Run 1
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Two electronswith ||<1,S:B ~ 20
One electronwith ||<1 andone with ||>1,S:B ~ 1
…but poor purity even in di-electron case
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Silicon tracking coverage to higher
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Using forward silicon hits in Run 1
1. Stand-alone silicon pattern recognition• Fit for 0, d0, pT (curvature) with 4 hits, <=1 dof.
• It worked, but was limited by • lever arm (L2)• Too few hits• Poor curvature resolution degraded impact parameter resolution• 4% relative increase in b-tagging for
top
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Using forward silicon hits in Run 1
2. Calorimeter-seeded tracking for electrons• Constrains pT and 0
• Adds 1 d.o.f.• Used same pattern recognition as
standard outside-in tracking• But, lever arm still too small to measure
curvature, just an initial direction so you have to rely on the calorimeter’s position measurement.
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eeET event
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eeET event
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Significant Improvements for Run II
SVX’ (Run 1)L00SVXII
ISL
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Intermediate Silicon Layers for Run II5 m2 of silicon
Intermediate Silicon Layers for Run II5 m2 of silicon
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Performance goals•8 layers over 30cm lever arm
•3x the lever arm•At 30 cm occupancy is low enough to attach single hits with minimal ambiguity because a typical jet, ~10 tracks in a <0.2 cone, covers 1000 channels
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•8 layers over 30cm lever arm•Sufficient pT resolution to
•Determine d0
•Determine charge over a large pT range
Performance goals
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•8 layers over 30cm lever arm•Sufficient pT resolution •Sufficient pointing resolution into COT to pick up more hits
•< 2 track resolution for ~ all pT
•~ hit resolution for pT>10 GeV•rz view is also comparable
•This will allow stand-alone, inside-out tracking once we reach design resolution.
2trk
COTres
Performance goals
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Silicon Commissioning in progress
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•Global ~finished
•Internal starting
But, even with a rough alignment we are now tracking forward electrons with a calorimeter seeded approach similar to the original Run 1 algorithm.
Alignment in progress
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Forward Electron Tracking Algorithm
1. Form 2 seed tracks,
one of each sign, from calorimeter
& beam spot
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Forward Electron Tracking Algorithm
1. Form 2 seed tracks,
one of each sign, from calorimeter
& beam spot
2. Project into silicon and attach hits
using standard silicon
pattern recognition
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Forward Electron Tracking Algorithm
1. Form 2 seed tracks,
one of each sign, from calorimeter
& beam spot
2. Project into silicon and attach hits
using standard silicon
pattern recognition
3. Select best 2 match
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Plug Alignment
COTPlug
Align plug to COT using the subset of COTtracks which match plug electrons just above||=1. Then align silicon to the COT.
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Plug Alignment
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Plug Alignment
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Measured using Z -> e+e- with one “leg” in the centralto reduce background and identify charge
Performance
1. Efficiency2. Fake Rate3. Charge MisId
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Performance
1. Efficiency~80% in Monte Carlo
~30% in data due to remaining commissioning effects
Improvements coming.
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Performance
1. Efficiency2. Fake Rate
…In progress…
In addition to the standardtechniques, we are pursuinga silicon occupancy measure.
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Performance
1. Efficiency2. Fake Rate3. Charge MisId
Comparable to COT for ||<1
because of CES resolution and
lever arm.
~ 10% for 1<||<2
Barely “non-random”for ||>2
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Future Improvements
1. AlignmentFor ||>2, need fullsilicon and PESresolution to determinecharge.
Meanwhile, can improvewith seed covariance pulls
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Future Improvements
1. Alignment
2. 3D hits
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Future Improvements
1. Alignment
2. 3D hits
3. Adding COT hits1 axial layer to ||~1.61 stereo layer to ||~2.0
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Future Improvements
1. Alignment
2. 3D hits
3. Adding COT hits
4. Muons IMU coverage to ||=1.5 fully within ISL and >= 1 axial COT superlayer
Momentum constraint becomes asymmetric but still powerful.
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Future Improvements
1. Alignment
2. 3D hits
3. Adding COT hits
4. Muons
5. Level 3 Trigger
Silicon outside-in trackingfor L3 will be ready soon.CAL seeded trackingis then a small, fast, addition
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Impact on acceptance
00.20.40.60.81
1.21.41.61.82
W WH top
Single electron case
Gain
, |
|<3
v.s
. |
|<1
Ideal
Wit
h ~
eff
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Impact on acceptance
0
1
2
3
4
5
6
7
Multi electron modesG
ain
, |
|<3
v.s
. |
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Ideal
Wit
h ~
eff
top WZ Z (800) HWWWWZ ZZ
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Our first step was using this for tracking Z e+e- with both e± in the plug.
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Now measuring charge asymmetry in W ± e ±
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~30 pb-1 processed so far
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Cross-check to COT in the central
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Improvements beyond statisticsAt highest , error currently dominated by charge IDAdding COT hits will significantly improve this.
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Conclusion
Calorimeter seeded algorithm implemented
Promising gains in acceptance
W asymmetry despite low luminosity
Electron ID is moving forward in Run II