Silicon Tracking for Forward Electron Identification at CDF

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Silicon Tracking for ForwardElectron
Identificationat CDF

• David Stuart,
• UC Santa Barbara
• Oct 30, 2002

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Outline

• Motivation and History
• CDF Run II upgrade
• Forward Tracking algorithm
• Physics Prospects

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In Run 1, CDF had tracking only in central region
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Physics beyond h1 e.g., look at h of e in Z ?
ee-
hlt1 50 hlt2 83
but what matters is finding both e and e-
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What is h of max h e? in Z ? ee-
hlt1 25 hlt2 70
ET gt 20 GeV
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More central at high mass, e.g. 800 GeV/c2 Z? ?
ee-
hlt1 53 hlt2 90
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Plug Electron ID in Run 1

• Some plug e ID
• Had/EM lt 0.05
• Isolation lt 0.1
• VTX Occupancy

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but poor purity even in di-electron case
Two electrons with hlt1, SB 20
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Silicon tracking coverage to higher h
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Using forward silicon hits in Run 1

• Stand-alone silicon pattern recognition
• Fit for f0, d0, pT (curvature)
• with 4 hits, lt1 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

• Calorimeter-seeded tracking for electrons
• Constrains pT and f0
• 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 calorimeters position measurement.

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eeggET event
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eeggET event
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Significant Improvements for Run II
ISL
SVXII
L00
SVX (Run 1)
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Intermediate Silicon Layers for Run II 5 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 Dflt0.2 cone,
• covers 1000 channels

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Performance goals

• 8 layers over 30cm lever arm
• Sufficient pT resolution to
• Determine d0
• Determine charge
• over a large pT
• range

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Performance goals

• 8 layers over 30cm lever arm
• Sufficient pT resolution
• Sufficient pointing resolution
• into COT to pick up more hits
• lt 2 track resolution for all pT
• hit resolution for pTgt10 GeV
• rz view is also comparable
• This will allow stand-alone,
• inside-out tracking once we
• reach design resolution.

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Silicon Commissioning in progress
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Alignment in progress

• 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.
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Forward Electron Tracking Algorithm

• Form 2 seed tracks,
• one of each sign,
• from calorimeter beam spot

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Forward Electron Tracking Algorithm

• Form 2 seed tracks,
• one of each sign,
• from calorimeter beam spot
• Project into silicon
• and attach hits using
• standard silicon pattern recognition

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Forward Electron Tracking Algorithm

• Form 2 seed tracks,
• one of each sign,
• from calorimeter beam spot
• Project into silicon
• and attach hits using
• standard silicon pattern recognition
• Select best c2 match

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Plug Alignment
Align plug to COT using the subset of COT tracks
which match plug electrons just above h1. Then
align silicon to the COT.
COT
Plug
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Plug Alignment
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Plug Alignment
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Performance

• Efficiency
• Fake Rate
• Charge MisId

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Performance

• Efficiency
• 80 in Monte Carlo
• 30 in data due to remaining
• commissioning effects
• Improvements coming.

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Performance

• Efficiency
• Fake Rate
• In progress
• In addition to the standard
• techniques, we are pursuing
• a silicon occupancy
• measure.

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Performance

• Efficiency
• Fake Rate
• Charge MisId
• Comparable to COT for hlt1
• because of CES resolution and
• lever arm.
• 10 for 1lthlt2
• Barely non-random
• for hgt2

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Future Improvements

• Alignment
• For hgt2, need full
• silicon and PES
• resolution to determine
• charge.
• Meanwhile, can improve
• with seed covariance pulls

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Future Improvements

• Alignment
• 3D hits

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Future Improvements

• Alignment
• 3D hits
• Adding COT hits
• 1 axial layer to h1.6
• 1 stereo layer to h2.0

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Future Improvements

• Alignment
• 3D hits
• Adding COT hits
• Muons
• IMU coverage to h1.5
• fully within ISL and gt 1
• axial COT superlayer
• Momentum constraint becomes
• asymmetric but still powerful.

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Future Improvements

• Alignment
• 3D hits
• Adding COT hits
• Muons
• Level 3 Trigger
• Silicon outside-in tracking
• for L3 will be ready soon.
• CAL seeded tracking
• is then a small, fast, addition

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Impact on acceptance
Single electron case
Gain, hlt3 v.s. hlt1
With eff
Ideal
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Impact on acceptance
Multi electron modes
Gain, hlt3 v.s. hlt1
With eff
Ideal
top
Z
WW
ZZ
WZ
Z? (800)
H?WW
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Our first step was using this for tracking Z ?
ee- with both e in the plug.
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Now measuring charge asymmetry in W ? e n
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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 statistics
At highest h, error currently dominated by charge
ID Adding COT hits will significantly improve
this.
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Conclusion
Calorimeter seeded algorithm implemented Promisin
g gains in acceptance W asymmetry despite low
luminosity
Electron ID is moving forward in Run II