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

2. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 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 · 10 32 cm -2 s -1 [10 12 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] The LHCb Experiment BsBs B tag K-K- K+K+ ++  +,K + p p PV ~1 cm SV

3. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 Role of the VELO in LHCb Reconstruction Trigger precise tracking primary/secondary vertices [lifetime] B-decay selection suppression of multiple interactions absolute luminosity measurement 4 Tm

4. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 Outline Design Module Production and Assembly Installation Control and DAQ Expected Performance Summary VELO alignment: see talk of M. Gersabeck

5. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 Layout 2 retractable detector halves 21 stations per half with an R and  sensor 2 Pile-Up stations per half [trigger] injection stable beams RF box module Pile-Up modules base LHC vacuum z x y x y 6 cm p p partly overlapping sensors IP

6. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 Sensors divided into quadrants pitch: 40 - 100  m divided into short and long strip region pitch: 35 - 100  m stereo angle r = 0.8 cm r = 4.2 cm 2048 strips  -sensor R-sensor type inverted not type inverted after 1 year of irradiation [2 fb -1 ] R [cm] U dep [V] n + in n-bulk sensors [300  m] inherently radiation tolerant strip isolation via p-spray expected radiation dose: - 1.3 · 10 14 n eq /cm 2 /year at r = 0.8 cm - 5 · 10 12 n eq /cm 2 /year at r = 4.2 cm after 3-4 years [~8 fb -1 ]: run partially depleted

7. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 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 CO 2 [silicon @ -7° C] carbon fibre paddle cooling block carbon fibre  -sensor R-side circuit  -side circuit R-sensor thermal pyrolytic graphite x y z

8. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 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  I/I (%) # module good stability during burn-in rejected bonding failure rate: Backend: 0.000 % Frontend: 0.010 % Sensorend: 0.002 % bad channels: R-sensors: 0.7 %  -sensors: 0.5 %

9. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 Fully Assembled VELO Half

10. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 Vacuum System LEFT DETECTOR BOX silicon detectors operated in vacuum RF shield of 300  m Al [3% Mg] - constitutes beampipe in VELO region - shape allows for overlapping sensors [alignment] avoid deformations:  P = P beam - P detector < 10 mbar requirements beam vacuum: P beam = 10 -8 mbar expected VELO vacuum: P detector < 10 -4 mbar This is what the LHC beams see …

11. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 Installation Lowering into the LHCb cavern … … ready for installation … … insertion of one half October 2007: installation of both VELO halves transport and installation without any damage [IV curves] installation rail RF box

12. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 Pumpdown [mbar] +2 mbar -5 mbar after 100 hours detector: 9 · 10 -5 mbar beam @ VELO: 2 · 10 -9 mbar [without ion pumps] absolute pressure differential pressure

13. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 DAQ and Control System

14. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 ARX GBE TTCRx CCPC 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 Gigabit Ethernet [GBE] max. L0 output rate: 1.1 MHz control via credit-card sized PC [CCPC] Readout Board (TELL1)

15. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 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 adjustment of timing to 0.65 ns problematic A-Rx card

16. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 Testbeam 10 modules 180 GeV  beam small scale CO 2 cooling system 6 modules readout simultaneously [full readout chain with final electronics boards] software: DAQ, ECS, tracking, vertexing, online monitoring x = 0 mm, d = 2 mm x = 15 mm, d = 5 mm 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 November 2006 y z x

17. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 binary resolution linear fit to data Testbeam Results  -sensors R-sensors S/N: 20 - 24 [decreases with r due to increasing strip length] resolution: 9 - 25  m [pitch: 40 - 100  m] S/N: 24 - 29 resolution: 9 - 20  m [pitch: 35 - 100  m] Landau  Gaussian active region R-sensors expected resolution improvements: cross-talk and  corrections R-sensors full sensor simulation

18. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 Expected Tracking Performance reconstructed track - hits in 3 stations LHCb acceptance: 1.9 <  < 4.9  = -ln tan(  /2) 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 B decays

19. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 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 CO 2 cooling system positioning system LV system

20. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 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 Summary

21. Backup Slides

22. Olaf BehrendtThe LHCb VErtex LOcatorINSTR08 Luminosity Measurement 10 -7 mbar Xe 10 11 p/bunch 30 Hz per bunch 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 test setup for gas injection expected beam size:  x ≈  y ≈ 70  m expected vertex resolution:  pv ≈ 30  m expected accuracy: ~1% LHCbmachine