The LHCb VErtex LOcator

1. The LHCb VErtex LOcator Olaf Behrendt on behalf of the VELO group Novosibirsk, 29.02.08

2. p+,K+ K- ~1 cm K+ Bs SV PV p+ p p Btag The LHCb Experiment • LHC experiment dedicated to heavy flavour physics • CP-violation and rare decays of beauty and charm hadrons • constrain unitarity triangles and search for new physics • forward spectrometer: 1.9<<4.9[bb-pairs produced correlated in space] • luminosity: 2·1032 cm-2s-1[1012 bb-pairs per year] Detector requirements: • reconstruction in harsh radiation environment • selective trigger system [bb-production cross-section small] • good vertex resolution [proper time] • good particle identification [K/ separation] INSTR08

3. Role of the VELO in LHCb 4 Tm Trigger Reconstruction • precise tracking • primary/secondaryvertices [lifetime] • B-decay selection • suppression of multiple interactions • absoluteluminosity measurement INSTR08

4. Outline • Design • Module Production and Assembly • Installation • Control and DAQ • Expected Performance • Summary • VELO alignment: see talk of M. Gersabeck INSTR08

5. y x z y x Layout base Pile-Up modules • 2 retractable detector halves • 21 stations per half with an R and  sensor • 2 Pile-Up stations per half [trigger] injection p 6 cm IP LHC vacuum stable beams module RF box p partly overlapping sensors INSTR08

6. Udep [V] after 1 year of irradiation [2 fb-1] not type inverted type inverted R [cm] Sensors r=4.2 cm -sensor R-sensor • divided into short and long strip region • pitch: 35-100 m • stereo angle r=0.8 cm • divided into quadrants • pitch: 40-100 m 2048 strips • n+ in n-bulk sensors [300 m] • inherently radiation tolerant • strip isolation via p-spray • expected radiation dose: • - 1.3 · 1014 neq/cm2/year at r = 0.8 cm • - 5 · 1012 neq/cm2/year at r = 4.2 cm after 3-4 years [~8 fb-1]: run partially depleted INSTR08

7. x y z Modules • double-sided hybrid to balance stresses due to “bi-metallic” effects • typical non-planarities: 250 m • sensor-sensor accuracy: < 10 m • analogue front-end read-out:2 x 16 Beetle chips • cooling: 2-phase CO2 [silicon @ -7° C] R-side circuit R-sensor carbonfibre -sidecircuit thermal pyrolytic graphite -sensor cooling block carbon fibrepaddle INSTR08

8. good stability during burn-in I/I (%) rejected # module Module Production receive and validate components hybrid assembly wire bonding on the hybrid glue sensors on hybrid wire bonding of sensors to hybrid glue to carbon-fibre paddle electrical check module metrology visual re-inspection module burn-in - electrical test in vacuum - thermal stress - electronics burn-in • bonding failure rate: • Backend: 0.000% • Frontend: 0.010% • Sensorend: 0.002% • bad channels: • R-sensors: 0.7% • -sensors: 0.5% INSTR08

9. Fully Assembled VELO Half INSTR08

10. Vacuum System • silicon detectors operated in vacuum • RF shield of 300 m Al [3% Mg] • constitutes beampipe in VELO region • shape allows for overlapping sensors [alignment] LEFT DETECTOR BOX • avoid deformations:P = Pbeam - Pdetector < 10 mbar • requirements beam vacuum: Pbeam = 10-8 mbar • expected VELO vacuum:Pdetector < 10-4 mbar This is what the LHC beams see … INSTR08

11. … ready for installation … … insertion of one half Installation Lowering into the LHCb cavern … RF box installation rail • October 2007: • installation of both VELO halves • transport and installation without any damage [IV curves] INSTR08

12. Pumpdown after 100 hours detector: 9 · 10-5 mbar beam @ VELO: 2 · 10-9 mbar [without ion pumps] [mbar] absolute pressure +2 mbar differential pressure -5 mbar INSTR08

13. DAQ and Control System INSTR08

14. ARX CCPC ARX ARX TTCRx ARX GBE Readout Board (TELL1) • originally developed for the VELO, now used for (almost) all of LHCb • analog input from 64 links • 10 bit analog to digital conversion @ 40 MHz [A-Rx] • pre-processing FPGAs[cross-talk, common mode, pedestals, clustering] • data sent out via GigabitEthernet [GBE] • max. L0 output rate: 1.1 MHz • control via credit-card sized PC [CCPC] INSTR08

15. adjustment of timing to 0.65ns problematic A-Rx card Commissioning installation of cables and boards Tests: • ADC cards [A-Rx] • Readout Boards [TELL1] • Control Boards • each readout slice • timing • cable check • noise level Control and DAQ system (almost) completely commissioned INSTR08

16. x = 15 mm, d = 5 mm x = 0 mm, d = 2 mm Testbeam • 10 modules • 180 GeV  beam • small scale CO2 cooling system • 6 modules readout simultaneously[full readout chain with final electronics boards] • software: DAQ, ECS, tracking, vertexing, online monitoring x z y November 2006 • data for 0, 4 and 8 degrees • interaction data- 4 layers with 2 Pb targets [300 m]- test vertex reconstruction- emulate open and closed VELO • > 50 million events to disk INSTR08

17. -sensors R-sensors Testbeam Results Landau  Gaussian • S/N: 20 - 24[decreases with r due to increasing strip length] • resolution: 9-25 m [pitch: 40-100 m] R-sensors binary resolution active region linear fit to data full sensor simulation • S/N: 24 - 29 • resolution: 9-20 m [pitch: 35-100 m] R-sensors expected resolution improvements: cross-talk and  corrections INSTR08

18. Expected Tracking Performance  = -ln tan(/2) B decays • For typical B decay modes: • primary vertex resolution:- x,y: ~10 m, z: ~60 m • proper time res.: ~40 fs • B mass res.: 12-25 MeV reconstructed track - hits in 3 stations LHCb acceptance: 1.9<<4.9 INSTR08

19. CO 2 positioning system LV system Status • module production and burn-in: completed March 2007 • module assembly on detector halves: completed March 2007 • vacuum/detector positioning system: installed • installation of detector halves:October 2007 • cooling system: installed • HV-/LV-system:installed • Electronic boards/cables: installed • system checkout: ongoing • system test foreseen within the next two months CO2 cooling system INSTR08

20. Summary • VErtex LOcator is small but complex detector • precision tracking very close to the interaction region • radiation tolerant design • results from the testbeam in November 2006 • S/N: 24-29 (), 20-24 (R) • resolution: 9-20 m (), 9-25 m (R) • on schedule for first beams in 2008 INSTR08

21. Backup Slides

22. 10-7 mbar Xe 1011 p/bunch 30 Hz per bunch test setup for gas injection Luminosity Measurement Method: • injection of a tiny bit of gas into VELO region • reconstruction of beam-gas interaction vertices- beam angles, profiles & relative positions- calculate luminosity • simultaneous reconstruction of beam-beam interaction vertices- calibrate ‘reference’ cross-section machine LHCb • expected beam size: x ≈ y ≈ 70 m • expected vertex resolution: pv ≈ 30 m expected accuracy: ~1% INSTR08