BTeV Pixel, Trigger and DAQ

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BTeV Pixel, Trigger and DAQ

• The BTeV pixel detector
• Sensor concept
• Test beam results
• Front end electronics
• System design
• The BTeV vertex trigger
• The BTeV DAQ scheme

Marina Artuso, Syracuse University
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Characteristics of hadronic b production
The higher momentum bs are at larger ?s
b production peaks at large angles with large bb
correlation
bg
?
b production angle
b production angle
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The BTeV Detector
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The Pixel Detector

• Pixels necessary to eliminate ambiguity problems
  with high track density essential to our
  detached vertex trigger
• Crucial for accurate decay length measurement
• Radiation hard
• Low noise

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Hybrid Silicon pixel devices

0.25 mm rad-hard FPIX2 chip

• Independent development and optimizations of
  readout chip and sensor
• n pixels on n-type substrates inter-pixel
  insulation technology under investigation
• Bump-bonding of flipped chip 2 technologies
  being considered Indium (In) and solder (SnPb)
  

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Pixel sensor design

• Test beam of Atlas p-stop and p-spray sensors
• 1st iteration of sensor submission of our own
  design SINTEF (in hand) and CSEM
• radiation hardness studies starting soon

Particle fluence on a pixel plane
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Readout electronics FPIX2

• Low noise
• Low and uniform threshold
• Feedback compensation allows to withstand high
  Ileak
• 3bit FADC in each cell

8 prefpix2 front-end cells
Test structures
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Readout electronics - Milestones

• 1997 FPIX0, a 12X64 HP 0.8u process
• Two stage front-end, analog output digitized off
  chip
• A data driven non-triggered RO
• Successfully used in beam tests
• 1998 FPIX1, a 18X160 Hp 0.5u process
• Two stage front-end, with one 2b FADC/cell.
• Fast triggered/non triggered RO
• Successfully used in beam tests
• 1999 preFPIX2_T, 2X160 TSMC 0.25u - tested for
  radiation tolerance

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Linearity before and after 33 Mrad
gt 7 max gain error. Believed to be due to
output buffer only.
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Noise and threshold distributions
gt Practically no change in noise and threshold
dispersion. gt 200 e- change in the threshold
voltage.
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The Fermilab pixel beam test

• Goals
• Measure the resolution as a function of the
  digitization accuracy, for different bias
  voltages and threshold applied (simulation
  validation)
• Measure pixel occupancy
• Compare different detector technologies (p-stop,
  ATLAS p-spray)

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Setup SSD telescope and DAQ
Magnet
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Factors affecting the spatial resolution
The interplay of these factors has been studied
with a Monte Carlo simulation including

• Energy deposition by charged track along its
  path length (Spread of the electron cloud due to
  diffusion
• Drift in E corresponding to doping and bias
  voltage applied
• E x B (our sensors will be in dipole field of 1.6
  T)
• Realistic parameters of the front end electronics
  (noise, threshold, digitization accuracy).

MIP crossing the sensor
E
E
Electrons drifting in the electric field and
spreading due to diffusion
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The charge signal in 280 mm Si (p-stop insulation
barriers)

• The signal peaks at the level expected for the
  Landau, but has a FWHM wider than theoretical
  Landau curve, but consistent with theoretical
  curve used in simulation (Bichsel, Rev. Mod.
  Phys. 60, (1988) 3.)

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Charge interpolation algorithms
(?(qr-ql)/(qrql)
S-curve (non linear)
Linear cog ok
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Spatial resolution

• Telescope tracking errors not included in
  simulation

Comparison FPIX0 beam test data and simulation
for binary and 8 bit analog readout
Comparison FPIX1 beam test data and simulation
for 2 bit analog readout and 2 values of threshold
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Effect of bias voltage applied
ST1 CiS FPIX0 detector
Nominal bias voltage
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Sensitivity of the resolution to the threshold
applied
ST1 CiS FPIX0 detector
Nominal threshold
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4 plane pixel telescope a couple of typical
events
1mm
Interaction vertex in the target
1mm
Interaction vertex in pixel plane
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Summary of test beam results

• We collected a very rich data sample that allowed
  us to perform several key measurements and to
  validate our understanding of the pixel sensors
• We verified that our front end design is adequate
  for our needs

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Multichip assembly
Optical driver
Optical receiver
Rad hard data serializer (CMS)
Control/monitoring/timing rad hard chip (FNAL)
?5 FPIX2 chips wirebonded to flex circuit
(multilayer capton)
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Pixel 1/2 plane
Integrated cooling channels
Fuzzy carbon structures machined as
shingles on which MCM modules will be attached
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Some prototype devices (ESLI)
Shingled detector
Nonporous carbon tubes
Heat exchanger test heated up by two aluminum
plates
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Decay Time Resolution

• Excellent decay time resolution
• Reduces background
• Allows detached vertex trigger
• The average decay distance and the uncertainty
  in the average decay distance are functions of B
  momentum
• ltLgt gbctB
• 480 mm x pB/mB

direct y
y from b
P(B?pp)(BTeV)
L/s
L/s
LHC-b region
CDF/D0 region
B momentum (GeV/c)
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Pixel Trigger Overview

• Idea Finds the primary vertex and identifies
  tracks which miss it, and calculates the
  significance of detachment, b/s(b).

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Three-level trigger system
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L1 Trigger Performance

• For a requirement of at least 2 tracks detached
  by more than 6s, we trigger on only 1 of the
  beam crossings and achieve the following
  efficiencies for these states after the other
  analyses cuts

State efficiency() state
efficiency() B ? pp- 63
Bo ? Kp- 63 Bs ? DsK
71 Bo ? J/y Ks 50 B- ? DoK-
70 Bs ? J/yK
68 B- ? Ksp- 27 Bo ?
ropo 56

• Full GEANT simulations including pattern
• recognition done for trigger

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Block diagram of proposed DAQ
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Summary

• Great progress has been achieved in the design of
  the sensor, front end electronics and module
  structure of the BTeV pixel detector
• Trigger and DAQ system will enable efficient
  collection of a variety of beauty decays
  provide a superb tool to challenge the Standard
  Model (see T. Skwarnicki talk)