26 june 2006imaging2006, stockholm, niels tuning 1/18 tracking with the lhcb spectrometer detector...

26 June 2006 Imaging2006, Stockholm, Niels Tuning 1/18

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 !HunenTilburg


LHCb in a nutshell

Both b’s are produced forward:

Aim: measure CP violation and rare decays

• pp with s =14 TeV

• L = 2.1032 cm-2s-1

• 1012 b-hadrons per year


The LHCb Detector


The LHCb Tracking System

Tracking Detectors

Outer TrackerNIKHEFCracowHeidelbergWarsaw

Trigger TrackerInner TrackerZurichLausanneSantiagoHeidelbergNovosibirsk

Vertex LocatorLiverpoolCERNGlasgowHeidelbergNIKHEFSyracuse


Tracks in LHCb


Vertex Locator

sensors

Rsensors

8mm

Vertex Tank

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 - 103μmthickness: 300μm

φ sensor: pitch: 39 μm - 98μmthickness: 300 μm


The Trigger Tracker

• Silicon sensors: 9.4*9.6 cm2, 500m thick

• Long modules of 14 sensors, with max 4 sensors per front-end (Beetle) 55pF

• Long Kapton cables front-end sensors

0.12 Tm

TT = Station before the magnet.

• Used in the trigger for momentum estimate

• Fringe field between magnet and VELO

z(m)


IT occupancy:

Hottest region = 2.3%

Beam Pipe

Outer Tracker :

Inner Tracker

595 cm

450

cm

The Outer and Inner Tracker

OT occupancy:

Average = 4.5%

Hottest region = 9%


The Inner Tracker

• 3 stations (T1 – T3)

• 4 detector boxes per station.

• Per box:

• 4 Silicon layers

• 4x7 modules (1 or 2 sensors each)

Beetle (0.25 m CMOS) front-end

Silicon sensor: p in n-bulk, 198m pitch, 420m and 300m thick.

1mm thick carbon sandwich

25m kapton isolation

Kapton hybrid

7.8cm

11cm


Outer Tracker

340 mm

Total nr of channels: 53.760

One large straw tube module: 34 x 490 cm2

4 x 64 = 256 straw tubes


Detector Beam TestsExample: Outer Tracker

r (mm)

Dri

ft ti

me

(ns)

rt-relation:

2.45 mm 2.45 mm

r (mm)

Eff

icie

ncy,

ε

efficiency profile:

Resolution and efficiency for different HV and amplifier threshold


OT Beam Test: Good Detector Performance

Eff

icie

ncy,

ε

Res

olut

ion

(mm

)

100

0.2

0

0

0.6

HV(V)1400 15501200

1400

• Good efficiency and resolution for HV > 1520 V ε 98% σ 200 µm

• Corresponds to Gain>50,000


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)


VELOTT

T2 T3T1

Outer tracker station

Tracking


The Expected Tracking Performance


Expected Tracking Performance (1)

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%Nmeas

Ntr

acks

effi

cien

cy

ghos

t rat

e

Expected Tracking Performance (2)

IP resolution

1/pt distribution for B tracks

42 mm

Vertex Locator

Momentum resolution

p distribution for B tracks

11cm

500c

m

Outer+Inner Tracker


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!


Backup

6 April 2006 20/18

Outer Tracker: Ageing?

• Where does it come from?• Why not observed in

dedicated test modules over the years (X-rays and protons) ??

Ratio of currents show signal loss• Damage upstream the gas

flow• All production sites• Irradiation with 55Fe and 90Sr• Electron microscope show

isolating layer of carbon

accumulated charge ≈1.3 C/cmNo effects seen

Ar/CO2 70/3020 l/hr

Gas Flow

Cha

nnel

Pos (cm)

Recommendation from experts

• Try to use Ar/CO2/O2 70/27/3

• Try H2O >5000 ppm

• Try more conditioning with reverse bias

Position1 485cm

L-wire 64

UL


Vertex Locator: Fast and Efficient

• Sufficient cluster efficiency (>99 %)

• Acceptable noise occupancy (<0.1 %)

• Low overspill (fake cluster rate from previous bunch crossing) (<25 %)

• Single cluster resolution: 10-20 μm

Overspill vs. S/N cut

Signal/Noise Cut

Noise occupancy vs. S/N cut

Signal/Noise CutTDC (ns)

S/N

rati

o

Pulse shape

25ns

0.1%25%

Radius (cm)

Clu

ste

r R

esolu

tion

20μm

10μm

1cm 4cm


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

See: LHCb-2005-076

beam

http://cdsweb.cern.ch/search.py?recid=896901&ln=en

26 june 2006imaging2006, stockholm, niels tuning 1/18 tracking with the lhcb spectrometer detector...

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