introduction silicon tracker project: design production tracking strategy and performance design and...

IntroductionSilicon Tracker project:

design production

Tracking strategy and performance

Design and performance of the LHCb Silicon Tracker

Kim VervinkEcole Polytechnique Fédérale de Lausanne

TIME 05 - Zurich

Oct 4, 2005 Kim Vervink 2

A huge one arm spectrometer.

p p

250 mrad

10 mrad

Dipole MagnetVertex Locator

Muon ChambersCalorimeters

Tracking Systems

Rich 1 & 2

Precision measurements of CP violation and rare decays in the B sector


Neighbouring detectors of the Silicon Tracker.

21 stations around the interaction point

The other subdetector that uses silicon

1m

Half discs open during beam injectionand close around the interaction point up until 8 mmWhole subdetector in vacuumSilicon thickness: 300 m

R – detector strip orientation

The vertex locator


the outer tracker

Outer Tracker 3 stations with 4 double planes

OT Straw tubes5mm diameterPitch 5,25 mm

4,7 m!

Module production going to completion


Silicon Tracker Project Some participants

Involved institutes: M.I.P. – Heidelberg E.P.F.L. – LausanneU.S.C. – Santiago de CompostelaUniZh – Zurich


Challenges of the Silicon Tracker.1. Large areas have to be covered in Silicon. The Silicon design is adapted in

order:• to keep it affordable • not to become overloaded in readout channels Long readout strips

Large distance between readout strips

2. Bunch crossings every 25ns fast shaping time

3. Momentum resolution is limited by multiple scattering minimization of material for the acceptance: Thin sensors

Increases noise Optimised front-end electronics

Thinner sensors make S/N go down Best compromise

Decreases S/N between strips optimise width/pitch of the strips

More load capacitance which increases the noise Beetle chip front-end designAdapted sensor thickness


Where is the Trigger Tracker?

VELO TT

Located behind the Velo & Rich 1

Just in front of the Magnet: still in frindge field

Active area of the detector covers full acceptance (cooling and electronics outside)

2 half stations in one box with in total 4 detector planes (0°, 5°, -5°, 0° orientation)


Trigger Tracker

Silicon sensors

Support rails

Interconnectcable

Pitch adaptor

Staggered front-end readout hybrids


Inner Tracker consists out of 3 stations, surrounded by the Outer Tracker

Where is the Inner Tracker?

VELO TT

Complete IT detector inside the acceptance (hybrids,pcb’s, cooling, cabling, …)

2 boxes with 2 Si-sensors modules 2 boxes with 1 Si-sensor modules

1,3 % of acceptance, 20% of tracks.


Cooling System

Readout Cables, High and Low voltage cables

Si-sensor

Kapton insulation

Carbon Fiber support layer:helps the cooling flow to the sensors

Airex foam

Aluminium Mini-Balcony

Pitch Adaptor + hybrid with Beetles.

Ladders are attached via the mini-balcony on a cooling rod, through which runs a cooling liquid detector is cooled (10°C) in order to control the thermal runaway


Silicon sensors for a fast and precise measurement.

TT IT

Type p+ microstrips on n type bulk

p+ microstrips on n type bulk

Dimensions (active area)

94,4mm x 94,6 mm

(93,9 mm x 91, 6 mm)

110 mm x 78 mm (108mm x 76mm)

Readout channels

512 384

Implant width 0,25 (w/p) 0,25 (w/p)

Pitch 198 m 183 m

Thickness 500 m 320 m or 410 m

HV input to the backside of the sensor

Bond pads &DC readout!

S/N value is above 12, taking into account the charge loss between strips.

Left strip Right strip


Production StatusTrigger Tracker: 2 half stations with 280 (+15% spare) readout sectors have to be buildInner Tracker: 3 stations with 336 (+15% spare) modules are to be produced and tested

A typical production trategy: Building of a module using jigs (parallel production)

MetrologyElectrical test using internal test pulses in order to find broken or unbonded strips

Schedual: Prototyping finished in August for both detectors Start of production All modules need to be fabricated by April 2006

Installation in the LHCb pit in June 2006 Status: Inner Tracker has about 20 modules produced Trigger Tracker has 13 modules fabricated

Inner trackertesting box


A Trigger Tracker module and burn-in test setup

TT burn-in test

4 modules

Cooling system

Burn-in box

A built TT module

Kapton readout cable

Hybrid

Sensor


Support and IT modules are in theproduction phase…

The 2nd short ladder module that was made…

Setup of the support frame


Silicon project: essential part for the tracking of the LHCb detector

Reconstruction is not a trivial task

LHCb gets about 50 primary particles per event: check….

30% radiation length between interaction point and Rich2Secondary particlesMultiple scatteringDegrades the momentum resolution

Interaction every 25 nsSpillover from previous bunch crossings


Tracking reconstruction

Particles spread out by magnet.

Bdl = 4 Tesla mWarm magnet

Top view

Multipass strategy• Long tracks• Ks after Velo• Only Velo and TT


First look for tracks that pass the whole tracking device (from Velo to T) Easiest to find Highest track resolution

The most important ones for physics studies

Start with a Velo Seed ( almost straight line: only position and direction known)

Adding one T station measurement to a Velo track Use optical parameterisation to calculate where the track passed using

zCenter and dSlope Use the other measurements of the T stations to confirm hypothesis

Fast algoritm: main tracking done in HLT Optical method parametrisation

Tracking strategy

zCenterdSlope


Second pass of long track reconstruction: work backwards

Seeding:Seeding in T stations using unused hitsThree hits define an ”almost” straight line Collect more hits around “trial track” to confirm your hypothesisAlso used to optimise Rich2 performance

Tracking:Transport the track seed to the Velo and compare with a Velo seed Look at the difference of track parameters Use ² criteria for matches

This method adds about 3% to the overall long track finding efficiency


Of the remaining hits, make tracks from particles that passed only in TT and IT/OT • Most are decay products of a Ks that decay outside VeLo• Look for unused seeds in the T stations and add hits in TT• Use optical method again.

Look amongst the remaining particles for hits in the Velo and TT stations alone. • Particles with low momentum: bent out by magnetic field• Look for unused Velo tracks with hits in the TT detector• Moderate efficiency (70%) and resolution (p/p ~ 15%) but used to

improve RICH 1 performance, kaon tagging and to find slow from D*

Other track types


Tracking Performance on long tracks

Momentum dependent: B particles have higher momentum Track finding efficiency ~95%

Cut out in physicsanalysis


Performance on the resolution of the momentum and the impact parameter (long tracks)


Summary

The design and prototyping of the Silicon Tracker subdetectors is finished.

Production of both the Silicon Tracker has started andInstallation in the LHCb pit is schedualed in June 2006.

Tracking performances are highly dependent on the quality of the Silicon Tracker detector.

A tracking strategy has been implemented, and its performance is satisfactory.

introduction silicon tracker project: design production tracking strategy and performance design and...

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