The LHCb Vertex Detector

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The LHCb Vertex Detector

• T. Bowcock
• University of Liverpool

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Overview

• Detector Design
• LHCb Components and Status
• Physics
• Vertex Detector
• Summary

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Detector Design(1)Goals

• A CP violation experiment
• Simultaneous measurements of ?,?,?, and ??
• Exploration of Bs sector
• Access to rare b-decays

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Detector Design(2)
a
g
b
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Detector Design(3)

• O(1012)bbpairs/year
• ?bb500?b
• ?bb/ ?inelastic510-3
• Pairs produced at small angles
• Modest luminosity

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LHCb(1)Components
Reversible field
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LHCb(2)Particle ID

• ID 1-150GeV/c

• RICH system divided into 2 detectors and 3
  radiators aerogel, C4F10, CF4

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LHCb(3)RICH

• Acceptance
• 300 mrad RICH 1
• 120 mrad RICH 2
• Radiators thickness L, refractive index n, angle
  ?c, ?/K threshold
• Aerogel C4F10 CF4
• L 5 85 167 cm
• n 1.03 1.0014 1.0005
• qc 242 53 32 mrad
• p 0.6 2.6 4.4 GeV
• K 2.0 9.3 15.6 GeV

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LHCb(4)Particle ID

• 3s separation pK 3-80GeV/c
• 2s separation pK 1-150GeV/c
• of detected photons
• 7 Aerogel 33 C4F10 18 CF4
  

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LHCb(5)Particle ID
Bd ? ?? ? (a)
Bs ? Ds?K? (g)
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LHCb(6)Vertex Detector - VELO
Series of disks
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LHCb(7)Status

• LHCb Experiment Approved Sep 1998
• Technical Design Reports
• Magnet
• Calorimeter
• Muon
• RICH
• VELO
• Outer Tracker

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LHCb(8)Improving Performance

• Reducing Material Budgets
• VELO 0.19X0 0.04?
• RICH1 0.14X0 0.05?
• Tracking 0.27X0 0.11?
• Beam Pipe
• VELO material, stations
• RICH Mirror
• Tracking Stations
• Trigger efficiencies

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Physics(1)2005

• BABAR, BELLE

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Physics(2)LHCb 200x
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Physics(4)LHCb Performance
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Physics(5)LHCb Performance
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Vertex Detector
Bs ? Ds K

• Precision tracking that
• B vertices
• lifetime (40fs)

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Vertex Detector

• Radiation Hard Sensors
• Analogue Electronics
• Precise Alignment
• Level 1 Trigger

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Geometry
Positioning and movement to 5mm
10cm
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UK

• Responsible for
• Sensors
• Hybrids
• Modules
• Cooling
• Alignment

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Operating Parameters

• Voltage
• Details of sensor technology
• Efficiency
• Temperature
• Mechanical construction
• Minimize cooling requirements
• Thickness
• Signal

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Damage
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LHC prediction (p-type)
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Depletion Voltages
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Depletion Voltages
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Operating Temp
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Sensor Design
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Sensors

• R-measuring-double metal

Al
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Testbeam
UK Purchased Hamamatsu prototypes-1998 to present
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Laboratory

• Irradiation of n-in-n and p-in-n Comparison with
  simulations
• Comparison of charge collection efficiency vs
  voltage curves obtained with beta particles
  (106Ru source) and 1060 nm laser
• Signal to noise with SCT128-VG
• Comparison of CCE with n and p read out strips
  (n-in-n vs p-in-n diode geometry)

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Technical Choices

• p bulk on n-bulk
• Isolation techniques (n-bulk)
• Individual p-stops (Hamamatsu)
• P-spray (Micron)
• Do these work in case of intense non-uniform
  irradiation?(PPESP)

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n-strip in n-bulk
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Non-uniform irradiation
ISE simulation of the electric field (120 V
applied bias) in the high gradient area of an
irradiated (gt6.1014 cm-2) n-in-n silicon detector
and signal of two neighbour strips generated by a
MIP crossing mid way of the two strips. The
difference in signal height corresponds to the
one obtained by moving the impact point of the
MIP off centre by half a micron.
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ISE simulation of the electric field (300 V
applied bias) in the high gradient area of an
irradiated (gt4.1014 cm-2) p-in-n silicon detector
and signal of two neighbour strips generated by a
MIP crossing mid way of the two strips
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Laser Injector
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Laser

• 2µm step which allows the intermediate
  positioning with 1 µm precision. The light spot
  has a FWHM of about 7µm.
• The metalisation on the backside of the detector
  has holes to avoid reflections of the laser
  light.

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Irradiation

• n-in-n and a p-in-n phi detectors have been
  irradiated

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The effective doping concentration as measured by
the CCE curves in correspondence of laser
illumination of different strips. The high
gradient region is about from strip 550 to 600.
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Measure ?
R
L
?R/(RL)
x
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Distortions-low gradient
Measurement of the h function in differently
irradiated area of the detector low gradient
area (irradiation about at type inversion
fluence)
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Distortions-high gradient
Measurement of the h function in differently
irradiated area of the detector high gradient
area
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Distortions-high dose
Measurement of the h function in differently
irradiated area of the detector most irradiated
area
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Laser versus MIPS
Comparison between CCE obtained with 1060 nm
laser and 106Ru source
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nn v pn
Preliminary comparison of CCE between n-in-n and
p-in-n detectors highly irradiated region. The
signal was induced by 1060 nm laser. The
detectors were irradiated together. Thickness of
both types 200 µm.
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Noise

• S/N with SCT128VG(LHC speed)on 200 micron thick
  n-bulk detectors
• 161 (uncorrected) unirradiated
• 141 highly irradiated
• Noise independent of bias 50-500V
• Operated up to 1000V

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Conclusions on Lab tests

• Distortion of the resolution due to
  non-homogeneous irradiation does not need
  correction
• CCE with n-strip read-out superior at low
  voltages after irradiation
• No evidence of microdischarges up to 500 V in
  n-in-n (p-spray) detectors
• 200 micron thick
• pn detectors(300micron) operated at 1000V

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Hybrid-SC128a

• IDEAS
• ?-detector
• Irradiated
• 1968-19-1
• 300?m Oxy

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Results with populated (12 chips) IDE hybrid and
irradiated 200µm p-in-n detector
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Kapton-SCT128a (IDEAS)
K-01
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Module(4)

• Alignment
• 5-10microns

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Curvature of Sensors
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Curvature
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Prototype Module

• Similar to TDR

Pipe slides through paddle
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Prototype Module

• Base simplified(?)
• Production in CF

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Prototype Module

• Single (asymmetric) Cooling Pipe

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VELO Module
Hybrid(SCT-VELO)
Base
Paddle
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VELO Sensor Support

• Substrate
• Hybrid(K-02)
• Fanins
• Sensor(200?m)
• Chips
• Adhesives
• Connectors

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Material Table
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Material Traversed
Tracks with uniform density in ?
Average
average
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Average
RL 2.87 0.00 0.00 0.19 0.06 0.01 0.09 0.01
0.06 0.16 0.25 0.00 0.01 0.32 0.02 0.11
0.01 Tot 4.18
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Hardware Module(1)

• Thermal models for TDR
• Cooling system
• Safety issues addressed

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Module
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Cooling System

• Safety compliant (factor 10!)
• certified
• Leak tested
• CO2 monitor

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Summary

• Second generation b-physics experiment
• day-one operation
• UK RD sensor development a success
• Vital to keep lead
• Superb instrument for exploring possible
  deviations from SM in B sector
• Preparation progressing well