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

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

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

4. 4 III LHC Symposium, Chia, Sardinia, 29 October 2001 Particle Identification  Excellent Particle Identification (  -K separation) required from 1 - 150 GeV/c o RICH system divided into 2 detectors and 3 radiators: aerogel, C 4 F 10, CF 4 Momentum vs polar angle Momentum

5. 5 III LHC Symposium, Chia, Sardinia, 29 October 2001 RICH1 RICH2 RICH System Overview o Acceptance –300 mrad RICH 1 –120 mrad RICH 2 o 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  c 242 53 32 mrad  0.6 2.6 4.4 GeV K 2.0 9.3 15.6 GeV Photo detectors

6. 6 III LHC Symposium, Chia, Sardinia, 29 October 2001 Photo Detectors Photo Detectors o Photo detector area: 2.6 m 2 o Single photon sensitivity: 200 - 600 nm, quantum efficiency > 20% o Good granularity: ~ 2.5 x 2.5 mm 2 o Large active area fraction:  73% o LHC speed read-out electronics: 40 MHz o LHCb environment: magnetic fields, charged particles Hybrid Photodiodes (HPD) baseline CF 4 Aerogel large rings C 4 F 10 small rings Multi-Anode PMT (backup)

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

8. 8 III LHC Symposium, Chia, Sardinia, 29 October 2001 HPD R&D Results Testbeam Cherenkov Photons Cherenkov Photons o Testbeam Setup –RICH 1 prototype –3 HPDs o Figure of merit –N 0  202 cm -1 (~35 PE/ring) Single photoelectron spectra visible

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

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

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

12. 12 III LHC Symposium, Chia, Sardinia, 29 October 2001 MAPMT (backup) o 8x8 dynode chains, pixel 2x2 mm 2 (effective size with lenses 3.2x3.2 mm 2 ) o Gain: 3. 10 5 at 800 V o UV glass window, bialkali photo cathode: QE = 22% at = 380 nm o Test beam data: 6.51  0.34 p.e. o Expect from simulation: 6.21 p.e. Multianode Photo Multiplier Tube o MAPMT active area fraction: 38% (includes pixel gap) o Increase with quartz lens with one flat and one curved surface to 85%

13. 13 III LHC Symposium, Chia, Sardinia, 29 October 2001 RICH1 Engineering Kapton beam-pipe seal Mirrors Photo detectors 14% X 0 Beam-pipe

14. 14 III LHC Symposium, Chia, Sardinia, 29 October 2001 Aerogel # photoelectrons vs. thickness 5cm transmission vs. dose LHCb 1 year 10 4 Gy o Hydroscopic Aerogel provides the best quality –clarity: 0.0045  m 4 /cm -1 –refractive index: 1.034 –radiation hard –Thickness: present choice 5 cm

15. 15 III LHC Symposium, Chia, Sardinia, 29 October 2001 o Baseline: glass mirrors with 3-leg spider (carbon fiber with screw adjusters) o Minimize dead material within acceptance Alternatives: glass 6mm : ~ 4.5% X 0, 1.5% l berillium 5mm : ~ 2% X 0, 1% l composite : ~ 1% X 0, 0.5% I spider prototype spider prototype adjuster very good repeatability & stability beam pipe 330 mrad acceptance one quadrant of spherical mirrors beam pipe RICH1 Mirrors

16. 16 III LHC Symposium, Chia, Sardinia, 29 October 2001 RICH2 Engineering entry window low mass beam pipe envelope supported by windows spherical mirrors on supporting planes exit window low mass photodetectors with individual magnetic shields magnetic shield box & backward lid (4 tons) to shield against magnetic stray field of ~150 Gauss frame plane mirrors 12.4% X 0

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

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

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

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

21. 21 III LHC Symposium, Chia, Sardinia, 29 October 2001 Photodetector Test Facilities o ~500 HPD or ~4000 MaPMT to be tested for: –functionality within specifications –individual characteristics –working parameters èfull automation needed o selection of detectors according to test results –position in detectors wrt. occupancy o to be operational in mid 2002 o 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) è2 test facilities needed for 1 1/2 years (Edinburgh & Glasgow) MaPMT test setup xy-table ODE MaPMT

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

23. 23 III LHC Symposium, Chia, Sardinia, 29 October 2001 RICH Alignment o Misalignment mirrors: fit photons from data to  = A cos(  sin(   In RICH2 (two mirrors): can only perform relative alignment  Minimise   for two mirror tilts  Photons from ambiguous mirror combinations (20%) degrade performance o Seed alignment <1 mrad for no degradation 1 mrad misalignment

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

25. 25 III LHC Symposium, Chia, Sardinia, 29 October 2001 B d ->    + o sensitive to CKM angle  o   ~ 2 0 - 5 0 in 1 year –depends on |P/T| and strong phase  o Backgrounds also have Tree T Penguin P

26. 26 III LHC Symposium, Chia, Sardinia, 29 October 2001 B s -> D s  K   Rate asymmetries measure angle  o Expect 2400 events in 1 year of data taking    

27. 27 III LHC Symposium, Chia, Sardinia, 29 October 2001 Conclusions o 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 3   -K separation from 3-80 GeV/c o LHCb RICH is progressing since 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 o In time to take data when LHC becomes operational in 2006