Impact parameter resolution study for ILC detector

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Impact parameter resolution study for ILC detector

• Tomoaki Fujikawa (Tohoku university)
• ACFA Workshop in Taipei
• Nov. 11 2004

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Outline
Study the pair ee- background hit rate for
vertex detector with various B fields.
(toolCAIN,Jupiter)
Optimize the vertex detector radii for each B
field.
Obtain the impact parameter resolutions with
optimized radii. (toolTRACKERR)
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Pair background hit rate study
Simulation tools

• CAIN

(for ee- pair background (dominant) generation)
Monte-Carlo program for the beam-beam
interaction. (by Yokoya-san)
Included interactions are
Jupiter
(for pair background hit rate estimation)
JLC Uniform Particle Interaction and Tracking
EmulatoR. GEANT4 based full simulator for ILC
(under construction)
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Beam parameters (input parameters for CAIN)
Beam parameters are similar to those in the TESLA
TDR.
crossing angle 7mrad.
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Detector configuration (for the Jupiter)
Detector is constructed with the Beam pipe,
Vertex detector (Ladder construction),
Intermediate tracker, Mask, etc. and base
geometry is Old one. (Namely, designed for
Warm machine.)
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The configuration of the vertex detector
These conditions are applied to estimate pair
background hit rate as first layer radius is
varied.
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Pair background hit rate for the vertex detector
1.hit point uniformity (for 1st. layer)
B 3tesla, R1 1.2cm.
Z
Z vs. phi
We can use the average hit rate to estimate the
occupancy.
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2. Number of fired pixels per track hit (for 1st.
layer)
Number of fired pixels per 1 track passage is
about 3.7. (independent of radius and B field)
Number of fired pixel per track hit
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3. Determination of first layer radius

• 20 readouts per train
• 3.7 fired pixels per track hit
• Pixel occupancy() hit rate (/bunch/cm2)
  0.326
• Set the first layer radius such that its pixel
  occupancy 0.5

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First layer hit rate vs. first layer radius
3 tesla
4 tesla
5 tesla
fit function
0.5 occupancy occurs at
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Impact parameter resolutions
Use TRACKERR program (also momentum
resolution). Assume pions.
TRACKERR
FORTRAN program to calculate tracking error
matrix with using cylindrically symmetric
system. Energy loss, energy loss fluctuation and
multiple scattering effects are included. Track
fitting uses Kalman filter.
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Detector configurations for TRACKERR
3 tesla
4 tesla
5 tesla
Beam pipe (Be)
VTX detector (Si pixel)
IT (Si strip)
TPC
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Impact parameter resolutions of the r-phi plane
Impact parameter resolutions are mostly the same
for each magnetic field case. (true for other
configurations with different thickness for BP
and VTX detector.)
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Other configuration results are as follows (at
polar angle 90 deg.)
For P 1GeV/c 3tesla is worse than 4(5) tesla by
12.0(19.2) . For P 10GeV/c 3tesla is worse
than 4(5) tesla by 6.4(8.8) .
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Momentum resolutions
Momentum resolution is better for high B at low
P, and better for low B at high P.
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Other configuration results are as follows (at
polar angle 90 deg.)
Momentum resolution is better for high B at low
P, and better for low B at high P.
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Comparison with other detector configurations
1. TESLA detector
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Comparison between TESLA and 3 tesla case
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Comparison between TESLA and 3 tesla case
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2.New VTX detector configuration (proposed by
Sugimoto-san)
Polystyrene foam
VTX detector
Layer
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Comparison between double and single layer (3
tesla)
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Comparison between double and single layer (3
tesla)
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Other configuration results
Momentum resolutions are mostly the same as
single layer case, but impact parameter
resolutions are different. (single layer case
does not have support design yet.)
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Summary and Plan
Summary

• Impact parameter resolution and momentum
  resolution are mostly the same in each B field
  case. (More detailed study (namely, b- and
  c-taging efficiency study) is needed to estimate
  the best B field.)
• Thickness of the detector components are quite
  important to obtain the good impact parameter
  resolution.

Plan
Estimate the impact parameter resolutions (and
more) by using a full simulator. (To do so,
development of the simulator is necessary)