Particle Identification in the LHCb Experiment

1. Particle Identification in the LHCb Experiment Paul Soler University of Glasgow and Rutherford Appleton Laboratory (on behalf of LHCb RICH group) III LHC Symposium on Physics and Detectors Chia, Sardinia, Italy. 29 October 2001.

2. Participating Institutes Sezione di Milano CERN Sezione di Genova University of Bristol University of Edinburgh University of Glasgow University of Oxford Imperial College Rutherford Appleton Laboratory III LHC Symposium, Chia, Sardinia, 29 October 2001

3. LHCb Experiment • LHCb Detector: forward single arm spectrometer Acceptance: 10-300 mrad bending 10-250 mrad non-bending RICH1 RICH2 III LHC Symposium, Chia, Sardinia, 29 October 2001

4. Particle Identification • Excellent Particle Identification (p-K separation) required from1 - 150 GeV/c Momentum vs polar angle Momentum • RICH system divided into 2 detectors and 3 radiators: aerogel, C4F10, CF4 III LHC Symposium, Chia, Sardinia, 29 October 2001

5. RICH System Overview RICH1 RICH2 Photo detectors • Acceptance • 300 mrad RICH 1 • 120 mrad RICH 2 • Radiators:thickness L, refractive index n, angle c, /K threshold Aerogel C4F10 CF4 L 5 85 167 cm n 1.03 1.0014 1.0005 qc 242 53 32 mrad p 0.6 2.6 4.4 GeV K 2.0 9.3 15.6 GeV III LHC Symposium, Chia, Sardinia, 29 October 2001

6. Photo Detectors C4F10 small rings Aerogel large rings • Photo detector area: 2.6 m2 • Single photon sensitivity:200 - 600 nm, quantum efficiency > 20% • Goodgranularity: ~ 2.5 x 2.5 mm2 • Large active area fraction:  73% • LHC speed read-out electronics: 40 MHz • LHCb environment: magnetic fields, charged particles CF4 Hybrid Photodiodes (HPD) baseline Multi-Anode PMT (backup) III LHC Symposium, Chia, Sardinia, 29 October 2001

7. Hybrid Photo Diodes (HPD) Pixel HPD (baseline) • Quartzwindow, thin S20 photocathodeQE dE = 0.77 eV • 32 x 32 Si pixel array: 500 m (Canberra) • ~450 tubes for RICH system • Cross-focusing optics • demagnification ~ 5 • 50 m point-spread function • 20 kV operating voltage • Encapsulated binary electronics • Tube, encapsulation: industry (DEP) -20 kV 61 pixel HPD • Existing prototype external read-out  = 80 mm III LHC Symposium, Chia, Sardinia, 29 October 2001

8. HPD R&D Results Testbeam • Testbeam Setup • RICH 1 prototype • 3 HPDs • Figure of merit • N0  202 cm-1 (~35 PE/ring) Cherenkov Photons Single photoelectron spectra visible III LHC Symposium, Chia, Sardinia, 29 October 2001

9. HPD Electronics • ALICE / LHCbdevelopment (0.25 m CMOS) • ALICE pixel size 50 m x 425 m • LHCb pixel size 62.5 m x 500 m 8 pixels = 1 LHCb super-pixel 500 m x 500 m • 40 MHz read-out clock • Bump bonding:chip-sensor Pixel chip Occupancy Max Mean RICH 1 8.2% 1.2% RICH 2 2.6% 0.4% 50 mm III LHC Symposium, Chia, Sardinia, 29 October 2001

10. Pixel HPD Chip Status • Chipsreceived: only operate up to 10 MHz(ALICE requirements) • Bump-bonding sensor-pixel chip: VTT Finland, good quality • Lab tests within LHCb requirements: • Threshold scans: ~700 e- (<2000 e-) • Noise: ~90 e- (<250 e-) • Signal: ~5000 e- • Wire bondingto ceramic carrier: Edgetek (Paris), good quality • LHCb chip redesign to achieve 40 MHz: submission IBM November • All current and voltage DACsredesigned and correctly layed-out • Improved uniformity of pulser • Clockskew being improved • HPD Pixel chip resubmission after October: review 31 October, 2001 HPD pixel chip assembly with ceramic carrier III LHC Symposium, Chia, Sardinia, 29 October 2001

11. Magnetic Field Tests • Prototype with a phosphor screen anode read out by a CCD (resolution ~150 mm) for magnetic field tests. • Distortions tolerable up to 10 Gauss • Flipping of B field shows no change in position residuals (within resolution). Axial field Transverse field III LHC Symposium, Chia, Sardinia, 29 October 2001

12. MAPMT (backup) Multianode Photo Multiplier Tube • 8x8 dynode chains, pixel2x2 mm2 (effective size with lenses 3.2x3.2 mm2) • Gain: 3.105 at 800 V • UV glass window, bialkali photo cathode: QE = 22% at  = 380 nm • Test beam data:6.51  0.34 p.e. • Expect from simulation:6.21 p.e. • MAPMT active area fraction: 38% (includes pixel gap) • Increase with quartz lens with one flat and one curved surface to 85% III LHC Symposium, Chia, Sardinia, 29 October 2001

13. RICH1 Engineering Photo detectors Beam-pipe 14% X0 Kapton beam-pipe seal Mirrors III LHC Symposium, Chia, Sardinia, 29 October 2001

14. LHCb 1 year 5cm 104 Gy # photoelectrons vs. thickness transmission vs. dose Aerogel • Hydroscopic Aerogel provides the best quality • clarity:0.0045 m4/cm-1 • refractive index:1.034 • radiation hard • Thickness:present choice5 cm III LHC Symposium, Chia, Sardinia, 29 October 2001

15. beam pipe adjuster spider prototype one quadrant of spherical mirrors RICH1 Mirrors • Baseline:glass mirrors with 3-leg spider (carbon fiber with screw adjusters) • Minimize dead materialwithin acceptance Alternatives: glass 6mm : ~ 4.5% X0 , 1.5% l berillium 5mm : ~ 2% X0 , 1% l composite : ~ 1% X0 , 0.5% I very good repeatability & stability beam pipe 330 mrad acceptance III LHC Symposium, Chia, Sardinia, 29 October 2001

16. RICH2 Engineering frame exit window low mass 12.4% X0 plane mirrors magnetic shield box & backward lid (4 tons) to shield against magnetic stray field of ~150 Gauss spherical mirrors on supporting planes photodetectors with individual magnetic shields beam pipe envelope supported by windows entry window low mass III LHC Symposium, Chia, Sardinia, 29 October 2001

17. RICH2 Engineering • Natural frequencies • Fundamental frequency ~6Hz Negligible movement • Finite Element Analysis: • Deflections under load (mag. shield 2x11000kg, tracker unit 200kg) • max. deflections <5mm achievable increasing deflection III LHC Symposium, Chia, Sardinia, 29 October 2001

18. 400Pa window RICH2 Gas Enclosure • Gas enclosure windows sealed at beam pipe and frame • 1mm fibre skins + 48mm PMI foam core: ~30mmat 400Pa • Stress on beam pipe sheet:@ 400Pa: ~1 ton • Photodetector window 1500x750x5 mm (two plates) • Optical transmission: >90% above 200 nm Tube Flange III LHC Symposium, Chia, Sardinia, 29 October 2001

19. RICH Electronics • Pixel chip • encapsulated, binary, 40 MHz, 32:1 MUX • Level 0 • on detector • Gbit optical links • clocks, triggers - TTC • Level 1 • in counting room • buffers data L1 latency, transports to DAQ • zero suppression • TTC, DCS interface III LHC Symposium, Chia, Sardinia, 29 October 2001

20. JTAG controller dTAP dTAP Light box L1 L0 dTAP X-y dTAP HPD assembly TTCrx OL PC S-link PCI-FLIC fpPINT TTCrx S-link HV HV control X-y controller Electronics Test Bench • Stand alone system for demonstration and test bench use • Nearly final setup (no TTCrx, ECS, DCS) available 01/2002 L1: stand alone or VME crate DAQ PC: DAQ & control L0: photo detector test bench III LHC Symposium, Chia, Sardinia, 29 October 2001

21. Photodetector Test Facilities • ~500 HPD or ~4000 MaPMT to be tested for: • functionality within specifications • individual characteristics • working parameters • full automation needed • selection of detectors according to test results • position in detectors wrt. occupancy • to be operational in mid 2002 • in the case of HPD’s: • use the electronics test-bench system • estimated time for all measurements & scans for one tube: 24hrs (including handling and resting in the dark) • 2 test facilities needed for 1 1/2 years (Edinburgh & Glasgow) MaPMT test setup ODE MaPMT xy-table III LHC Symposium, Chia, Sardinia, 29 October 2001

22. Ultrasound Fabry-Perot RICH Gas and Monitoring • by LHC Gas group • control & monitor p & T • Ultrasound gas monitor: • Measure variation of sound speed v = (RT/M)1/2 • monitor gas compositionFabry-Perot monitor: • Measure fringes (depend on distance d, , and n) • monitor dispersion n() RICH-2 additional monitor systems III LHC Symposium, Chia, Sardinia, 29 October 2001

23. RICH Alignment • Misalignment mirrors: fit photons from data to Dq = A cos(f) + B sin(f) • In RICH2 (two mirrors): can only perform relative alignment • Minimise c2for two mirror tilts • Photons from ambiguous mirror combinations (20%) degrade performance • Seed alignment <1 mrad for no degradation 1 mrad misalignment III LHC Symposium, Chia, Sardinia, 29 October 2001

24. RICH Performance 3s -K separation 3-80 GeV/c (2s 1-150 GeV/c) • Simulation • based on measured test beam HPD data • global pattern recognition • background photons included • # of detected photons • 7 Aerogel 33 C4F10 18 CF4 • Angular resolution[mrad] • 2.00 Aerogel 1.45 C4F10 0.58 CF4 III LHC Symposium, Chia, Sardinia, 29 October 2001

25. Bd ->  + • sensitive to CKM angle  •  ~ 20 - 50in 1 year • depends on |P/T| and strong phase  • Backgrounds also have Penguin P Tree T III LHC Symposium, Chia, Sardinia, 29 October 2001

26. Bs -> DsK • Rate asymmetries measure angleg-2dg • Expect 2400 events in 1 year of data taking • s(g-2dg) = 60 .. 140 III LHC Symposium, Chia, Sardinia, 29 October 2001

27. Conclusions • Physics performance studies show that the RICH is essential for the LHCb physics programme. • The RICH design of LHCb with two detectors and three radiators provides 3sp-K separation from 3-80 GeV/c • LHCb RICH is progressingsince TDR • Pixel HPD chip has incurred a delay but is not in critical path (project under review). • Design for subsystems are detailed and advanced • Transition from R&D to construction • In time to take data when LHC becomes operational in 2006 III LHC Symposium, Chia, Sardinia, 29 October 2001