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.

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

III LHC Symposium, Chia, Sardinia, 29 October 2001 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

Particle Identification Momentum vs polar angle Momentum RICH system divided into 2 detectors and 3 radiators: aerogel, C4F10, CF4 Excellent Particle Identification (p-K separation) required from 1 - 150 GeV/c III LHC Symposium, Chia, Sardinia, 29 October 2001

III LHC Symposium, Chia, Sardinia, 29 October 2001 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

III LHC Symposium, Chia, Sardinia, 29 October 2001 Photo Detectors C4F10 small rings Aerogel large rings Photo detector area: 2.6 m2 Single photon sensitivity: 200 - 600 nm, quantum efficiency > 20% Good granularity: ~ 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

Hybrid Photo Diodes (HPD) Quartz window, thin S20 photo cathode 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) Pixel HPD (baseline) -20 kV 61 pixel HPD Existing prototype external read-out  = 80 mm III LHC Symposium, Chia, Sardinia, 29 October 2001

III LHC Symposium, Chia, Sardinia, 29 October 2001 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

III LHC Symposium, Chia, Sardinia, 29 October 2001 HPD Electronics Pixel chip Occupancy Max Mean RICH 1 8.2% 1.2% RICH 2 2.6% 0.4% ALICE / LHCb development (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 50 mm III LHC Symposium, Chia, Sardinia, 29 October 2001

Pixel HPD Chip Status Chips received: 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 bonding to ceramic carrier: Edgetek (Paris), good quality 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 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

III LHC Symposium, Chia, Sardinia, 29 October 2001 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

III LHC Symposium, Chia, Sardinia, 29 October 2001 MAPMT (backup) Multianode Photo Multiplier Tube 8x8 dynode chains, pixel 2x2 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

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

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

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

RICH2 Engineering frame exit window plane mirrors magnetic shield box 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

III LHC Symposium, Chia, Sardinia, 29 October 2001 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

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

III LHC Symposium, Chia, Sardinia, 29 October 2001 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

Electronics Test Bench Stand alone system for demonstration and test bench use Nearly final setup (no TTCrx, ECS, DCS) available 01/2002 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 L0: photo detector test bench L1: stand alone or VME crate DAQ PC: DAQ & control III LHC Symposium, Chia, Sardinia, 29 October 2001

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

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

III LHC Symposium, Chia, Sardinia, 29 October 2001 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 c2 for 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

III LHC Symposium, Chia, Sardinia, 29 October 2001 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

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

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

III LHC Symposium, Chia, Sardinia, 29 October 2001 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 3s p-K separation from 3-80 GeV/c 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 In time to take data when LHC becomes operational in 2006 III LHC Symposium, Chia, Sardinia, 29 October 2001