1. Introduction Silicon Tracker project: design production Tracking strategy and performance Design and performance of the LHCb Silicon Tracker Kim Vervink Ecole Polytechnique Fédérale de Lausanne TIME 05 - Zurich

2. Oct 4, 2005Kim Vervink2 A huge one arm spectrometer. p p 250 mrad 10 mrad Dipole Magnet Vertex Locator Muon Chambers Calorimeters Tracking Systems Rich 1 & 2 Precision measurements of CP violation and rare decays in the B sector

3. Oct 4, 2005Kim Vervink3 Neighbouring detectors of the Silicon Tracker. 21 stations around the interaction point The other subdetector that uses silicon 1m Half discs open during beam injection and close around the interaction point up until 8 mm Whole subdetector in vacuum Silicon thickness: 300  m R –  detector strip orientation The vertex locator

4. Oct 4, 2005Kim Vervink4 the outer tracker Outer Tracker 3 stations with 4 double planes OT Straw tubes 5mm diameter Pitch 5,25 mm 4,7 m! Module production going to completion

5. Oct 4, 2005Kim Vervink5 Silicon Tracker Project Some participants Involved institutes: M.I.P. – Heidelberg E.P.F.L. – Lausanne U.S.C. – Santiago de Compostela UniZh – Zurich

6. Oct 4, 2005Kim Vervink6 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 design  Adapted sensor thickness

7. Oct 4, 2005Kim Vervink7 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)

8. Oct 4, 2005Kim Vervink8 Trigger Tracker Silicon sensors Support rails Interconnect cable Pitch adaptor Staggered front-end readout hybrids

9. Oct 4, 2005Kim Vervink9 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.

10. Oct 4, 2005Kim Vervink10 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

11. Oct 4, 2005Kim Vervink11 Silicon sensors for a fast and precise measurement. TTIT Typep+ 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 512384 Implant width0,25 (w/p) Pitch 198  m183  m Thickness 500  m320  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

12. Oct 4, 2005Kim Vervink12 Production Status Trigger Tracker: 2 half stations with 280 (+15% spare) readout sectors have to be build Inner 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) Metrology Electrical 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 tracker testing box

13. Oct 4, 2005Kim Vervink13 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

14. Oct 4, 2005Kim Vervink14 Support and IT modules are in the production phase… The 2 nd short ladder module that was made… Setup of the support frame

15. Oct 4, 2005Kim Vervink15 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 Rich2  Secondary particles  Multiple scattering  Degrades the momentum resolution Interaction every 25 ns  Spillover from previous bunch crossings

16. Oct 4, 2005Kim Vervink16 Tracking reconstruction Particles spread out by magnet. Bdl = 4 Tesla m Warm magnet Top view Multipass strategy Long tracks Ks after Velo Only Velo and TT

17. Oct 4, 2005Kim Vervink17 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 zCenter dSlope

18. Oct 4, 2005Kim Vervink18 Second pass of long track reconstruction: work backwards Seeding: Seeding in T stations using unused hits Three hits define an ”almost” straight line Collect more hits around “trial track” to confirm your hypothesis Also 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

19. Oct 4, 2005Kim Vervink19 Of the remaining hits, make tracks from particles that passed only in TT and IT/OT Most are decay products of a K s 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

20. Oct 4, 2005Kim Vervink20 Tracking Performance on long tracks Momentum dependent: B particles have higher momentum Track finding efficiency ~95% Cut out in physics analysis

21. Oct 4, 2005Kim Vervink21 Performance on the resolution of the momentum and the impact parameter (long tracks)

22. Oct 4, 2005Kim Vervink22 Summary The design and prototyping of the Silicon Tracker subdetectors is finished. Production of both the Silicon Tracker has started and Installation 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.