1. The Ring Imaging Cherenkov Detectors for LHCb Antonis Papanestis CCLRC – RAL On behalf of the LHCb RICH group

2. HEP 2005 Lisbon1/16 The LHCb Detector A forward single arm spectrometer RICH1 RICH2 VELO Magnet Tracker Calorimeter Muon

3. HEP 2005 Lisbon2/16 b production at the LHC LHCb acceptance: 300 mrad horizontal 250 mrad vertical LHCb luminosity: 2×10 32 cm -2 s -1 to avoid multiple interactions production favours small polar angles and same hemisphere

4. HEP 2005 Lisbon3/16 LHCb RICH System Two detectors, three radiators RICH1: Aerogel 2→10 GeV/c n=1.03 (nominal at 540 nm) C4F10 up to 70 GeV/c n=1.0014 (nominal at 400 nm) Acceptance: 25→250 mrad (vertical) 300 mrad (horizontal) RICH2: CF4 up to 100 GeV/c n =1.0005 (nominal at 400 nm) Acceptance: 15→100 mrad (vertical) 120 mrad (horizontal)

5. HEP 2005 Lisbon4/16 RICH1 (1) HPD plane: 7 columns, 14 tubes each Magnetic shield box Vertical X-section

6. HEP 2005 Lisbon5/16 RICH1 (2) Optimised for:  Low material budget  Beryllium mirrors 4 mm Be, 0.5 mm glass  Exit window: PMI (polymethacryli- mide) foam between carbon fibre epoxy skins  High (60 mT) magnetic fields  Magnetic shields 8 tonnes of “Armco” iron each

7. HEP 2005 Lisbon6/16 Aerogel Silica Aerogel:  fragile linked network of SiO 2 nanocrystals  Density = 0.15 g/cm 3  Nominal n=1.03 at 540 nm  Transparency 35% at 400 nm (4 cm tile)  Hygroscopic

8. HEP 2005 Lisbon7/16 Aerogel testbeam Aerogel Thickness Light yield Per Event (N photons ) Cherenkov Angle in mrad. θ C σ θ 4 cm DATA MC 9.7 ± 1.0 11.5 ± 1.2 250.0 5.4 248.7 4.0 8 cm DATA MC 12.2± 1.3 14.7 ±1.6 246.8 5.8 245.0 3.9 Published in NIMA 519(2004) 493 with 4 pad-HPD DATA and MONTECARLO

9. HEP 2005 Lisbon8/16 RICH2 schematic X Beam Axis-  RICH2 Optics Top View Z Spherical Mirror Flat Mirror Photon funnel+Shielding Central Tube Mirror Support Panel Z Y X Support Structure

10. HEP 2005 Lisbon9/16 RICH2 under construction Spherical mirrors (56) in place and aligned. Flat mirrors (40) delivered, installation almost complete. Final leakage test after the windows are placed back. To be installed at the end of August.

11. HEP 2005 Lisbon10/16 RICH2 mirror alignment 2 mm Alignment and stability set a 50 μrad contribution to the overall uncertainty in the single photon Cherenkov angle reconstruction All mirrors from one side

12. HEP 2005 Lisbon11/16 Hybrid Photon Detectors Main features: Total coverage 2.6 m 2 (active 65%) Granularity of 2.5 X 2.5 mm 2 Sensitive in 200  600 nm 40 MHz readout Tolerant well beyond 3 kRad/year Binary output Tube Ø: 83 mm S20 photocathode: 75 mm Ø active

13. HEP 2005 Lisbon12/16 HPD testing Thorough HPD testing LHCb quality assurance: 2 photon detector test facilities 1 HPD per work day per facility over production period of ~18 months Production rate: 30 HPDs per month over production period of ~18 months ← 100 mm →

14. HEP 2005 Lisbon13/16 System test HPD column mechanics Mirror Bea m Accumulated rings in C 4 F 10 Beam Pipe Radiator vessel HPD housing

15. HEP 2005 Lisbon14/16 Software Custom simulation of Cherenkov light production allowed the study and optimisation of the various system parameters. LHCb now use a C++ OO framework (Gaudi) and have incorporated Geant 4 in the framework Geometry DB (xml) PYTHIAEVTGEN Geant4 simulation Simulated data DigitisationData (real or simulated) ReconstructionPhysics Analysis Gaudi is a very flexible framework that simplifies the introduction and testing of new pattern recognition algorithms. Currently testing the use of RICH information in High Level Trigger

16. HEP 2005 Lisbon15/16 RICH performance (in full detector realistic simulation) Particle Momentum (GeV/c) K  K or P   K or P   e,  or  K  e,  or  0 20 40 60 80 100 Particle Momentum (GeV/c) Efficiency (in %) of pion and kaon identification and Probability (in %) of misidentifying pion and kaon 0 20 40 60 80 100

17. HEP 2005 Lisbon16/16 Conclusions  RICH is an essential part of LHCb  RICH2 almost ready for installation, RICH1 under construction  Production of HPDs started  Pre-series OK  LHCb will produce physics from day one of LHC running

18. HEP 2005 Lisbon17/16

19. HEP 2005 Lisbon18/16 HPD anode Ceramic carrier Glue Chip+sensor High T cure Wire- bonding

20. HEP 2005 Lisbon19/16 HPD flowchart Tube body assembly Photo-cathode deposition and vacuum sealing Anode incoming inspection and testing Anode testing Final HPD testing HPD cabling and potting QE measurement and anode testing Vacuum bake-out @ 300°C