1. Tracking with the LHCb Spectrometer Detector Performance and Track Reconstruction
Niels Tuning (Outer Tracker Group LHCb)
NIKHEF Amsterdam, The Netherlands
Tracking detectors in LHCb
Detector construction
Detector performance
Tracking performance
Many thanks to Jeroen van !
Hunen
Tilburg
26 June 2006
Imaging2006, Stockholm, Niels Tuning

2. Imaging2006, Stockholm, Niels Tuning
LHCb in a nutshell
pp with s =14 TeV
L = cm-2s-1
1012 b-hadrons per year
Both b’s are produced forward:
Aim: measure CP violation and rare decays
26 June 2006
Imaging2006, Stockholm, Niels Tuning

3. Imaging2006, Stockholm, Niels Tuning
The LHCb Detector
26 June 2006
Imaging2006, Stockholm, Niels Tuning

4. The LHCb Tracking System
Tracking Detectors
Vertex Locator
Liverpool
CERN
Glasgow
Heidelberg
NIKHEF
Syracuse
Trigger Tracker
Inner Tracker
Zurich
Lausanne
Santiago
Heidelberg
Novosibirsk
Outer Tracker
NIKHEF
Cracow
Heidelberg
Warsaw
26 June 2006
Imaging2006, Stockholm, Niels Tuning

5. Imaging2006, Stockholm, Niels Tuning
Tracks in LHCb
26 June 2006
Imaging2006, Stockholm, Niels Tuning

6. Imaging2006, Stockholm, Niels Tuning
Vertex Locator
Vertex Tank f
sensors R
8mm
42 mm
Si sensor
n+-on-n
2048 channels, analog readout
non-uniform radiation environment
13(0.5) 1013 neq/cm2/yr at R=8(42)mm
R sensor:
pitch: 38 μm - 103μm
thickness: 300μm
φ sensor:
pitch: 39 μm - 98μm
thickness: 300 μm
26 June 2006
Imaging2006, Stockholm, Niels Tuning

7. Imaging2006, Stockholm, Niels Tuning
The Trigger Tracker
TT = Station before the magnet.
Used in the trigger for momentum estimate
Fringe field between magnet and VELO
Silicon sensors: 9.4*9.6 cm2, 500m thick
Long modules of 14 sensors, with max 4 sensors per front-end (Beetle)  55pF
Long Kapton cables front-end  sensors
0.12 Tm
 z(m)
26 June 2006
Imaging2006, Stockholm, Niels Tuning

8. The Outer and Inner Tracker
Outer Tracker :
Inner Tracker
595 cm
450 cm
IT occupancy:
Hottest region = 2.3%
OT occupancy:
Average = 4.5%
Hottest region = 9%
Beam Pipe
26 June 2006
Imaging2006, Stockholm, Niels Tuning

9. Imaging2006, Stockholm, Niels Tuning
The Inner Tracker
Silicon sensor: p in n-bulk, 198m pitch, 420m and 300m thick.
7.8cm
1mm thick carbon sandwich
25m kapton isolation
11cm
3 stations (T1 – T3)
4 detector boxes per station.
Per box:
4 Silicon layers
4x7 modules (1 or 2 sensors each)
Kapton hybrid
Beetle (0.25 m CMOS) front-end
26 June 2006
Imaging2006, Stockholm, Niels Tuning

10. Imaging2006, Stockholm, Niels Tuning
Outer Tracker
One large straw tube module:
34 x 490 cm2
4 x 64 = 256 straw tubes
340 mm
Total nr of channels:
53.760
26 June 2006
Imaging2006, Stockholm, Niels Tuning

11. Detector Beam Tests Example: Outer Tracker
rt-relation:
efficiency profile:
Drift time (ns)
Efficiency, ε
r (mm)
r (mm)
2.45 mm
2.45 mm
 Resolution and efficiency for different HV and amplifier threshold
26 June 2006
Imaging2006, Stockholm, Niels Tuning

12. OT Beam Test: Good Detector Performance
Good efficiency and resolution for HV > 1520 V
ε  98%
σ  200 µm
Corresponds to Gain>50,000
0.6
Resolution (mm)
0.2
1400
100
Efficiency, ε
1200
1400
1550
HV(V)
26 June 2006
Imaging2006, Stockholm, Niels Tuning

13. Imaging2006, Stockholm, Niels Tuning
LHCb Tracking
VELO
seeds
Long track (forward)
Long track (matched)
T seeds
Upstream track
Downstream track
T track
VELO track
T tracks  useful for RICH2 pattern recognition
Long tracks  highest quality for physics (good IP & p resolution)
Downstream tracks  needed for efficient KS finding (good p resolution)
Upstream tracks  lower p, worse p resolution, but useful for RICH1 pattern recognition
VELO tracks  useful for primary vertex reconstruction (good IP resolution)
26 June 2006
Imaging2006, Stockholm, Niels Tuning

14. Imaging2006, Stockholm, Niels Tuning
Tracking
Outer tracker station
VELO TT T1 T2 T3
26 June 2006
Imaging2006, Stockholm, Niels Tuning

15. The Expected Tracking Performance
26 June 2006
Imaging2006, Stockholm, Niels Tuning

16. Expected Tracking Performance (1)
Nmeas
Ntracks
Long tracks
~38 measurements per track
Efficiency >95% (for p>12GeV)
Ghost rate <7% (for p>12GeV)
Robust: track multiplicity x2:
efficiency 91%
ghost rate 14%
efficiency
ghost rate
26 June 2006
Imaging2006, Stockholm, Niels Tuning

17. Expected Tracking Performance (2)
IP resolution
1/pt distribution for B tracks
42 mm
Vertex Locator
Momentum resolution
p distribution for B tracks
11cm
500cm
Outer+Inner Tracker

18. Imaging2006, Stockholm, Niels Tuning
Conclusions
Construction of the LHCb tracking system well advanced
Vertex Locator: 8 ‘pre-series’ modules produced (out of 84)
Trigger Tracker: 80 half modules in production (need 128)
Outer Tracker: All modules produced
Inner Tracker: 100 modules produced & 60 are fully tested (need 336)
Expected performance (for p>12 GeV):
tracking efficiency >95%
ghost rate <7%
(B-meson decay time resolution is 37 fs !)
Detectors are being shipped to CERN for
installation!
26 June 2006
Imaging2006, Stockholm, Niels Tuning

19. Imaging2006, Stockholm, Niels Tuning
Backup
26 June 2006
Imaging2006, Stockholm, Niels Tuning

20. Vertex Locator: Fast and Efficient
TDC (ns)
S/N ratio
Pulse shape
25ns
Noise occupancy vs. S/N cut
Signal/Noise Cut
Overspill vs. S/N cut
Signal/Noise Cut
0.1%
25%
Radius (cm)
Cluster Resolution
20μm
10μm
1cm
4cm
Sufficient cluster efficiency (>99 %)
Acceptable noise occupancy (<0.1 %)
Low overspill (fake cluster rate from previous bunch crossing) (<25 %)
Single cluster resolution: μm
26 June 2006
Imaging2006, Stockholm, Niels Tuning

21. Outer Tracker Beam Test
Final detector modules
Final prototype electronics
6 GeV electrons at DESY
Efficiency
Resolution
Noise
Cross talk HV
Amplifier threshold
Position along straw vs
beam
See: LHCb
26 June 2006
Imaging2006, Stockholm, Niels Tuning