1. An overview of the LHCb RICH detectors RICH 2007 Trieste 15-20 Oct 2007 Neville Harnew University of Oxford On behalf of the LHCb RICH Collaboration

2. 2 RICH 2007 15-20 October, Trieste N. Harnew Outline of the talk n The LHCb Experiment n The RICH status wRICH1 wRICH2 n The Hybrid Photon Detector (HPD) project n RICH2 commissioning n RICH calibration n Performance n Summary

3. 3 RICH 2007 15-20 October, Trieste N. Harnew The LHCb Detector Acceptance Vertical 250mrad Horizontal 300mrad to 10 mrad Two RICH detectors provide  /K/p identification Forward spectrometer (running in pp collider mode). A dedicated B-physics experiment at the LHC

4. 4 RICH 2007 15-20 October, Trieste N. Harnew LHCb detector in place, commissioning is well underway…. RICH1RICH2

5. 5 RICH 2007 15-20 October, Trieste N. Harnew C 4 F 10 gas n=1.0014 Up to ~70 GeV/c CF 4 gas n=1.0005 Beyond ~100 GeV/c Silica Aerogel n=1.03 1-10 GeV/c The RICH Radiators AerogelC 4 F 10 CF 4 5.324.018.4 RICH1 : 25  250 mrad vertical 25  300 mrad horizontal RICH2 : 15  100 mrad vertical, 15  120 mrad horizontal Expected photon yields – for isolated saturated particles

6. 6 RICH 2007 15-20 October, Trieste N. Harnew The LHCb RICH Detectors 1m 4m

7. 7 RICH 2007 15-20 October, Trieste N. Harnew RICH1 schematic : “vertical” geometry 4m Upper Magnetic Shielding Protects HPDs from B field, supports upper HPDs Spherical Mirrors Lightweight carbon fibre mirrors 1.5% radiation length Glass Planar Mirrors Beryllium beampipe (defines RICH1 inner acceptance) VELO Exit Window 2mm aluminium.. Sealed to gas enclosure. No RICH entrance window. Photon detector plane 14 by 7 Hybrid Photon Detectors (HPDs) Quartz Window Gas Enclosure supports mirrors and aerogel, contains C 4 F 10 RICH1 Exit Window Carbon fibre & PMMI foam Sealed direct to the beampipe. Lower Photon detector plane Mounted on lower shield Lower Magnetic Shielding mounted on cavern floor, supports lower HPDs and Gas Enclosure

8. 8 RICH 2007 15-20 October, Trieste N. Harnew RICH1 Magnetic shielding RICH1 picture gallary Gas Enclosure before installation Trial installation of the HPD box Gas enclosure and mirrors installed in LHCb pit Beryllium beampipe, VELO exit window and seal and planar mirrors

9. 9 RICH 2007 15-20 October, Trieste N. Harnew The RICH1 Mirrors Carbon Fibre Mirrors: 1.5% radiation length Glass planar mirrors Spherical mirrors See talk by Fabio Metlica

10. 10 RICH 2007 15-20 October, Trieste N. Harnew  16 aerogel tiles for RICH1. Produced by Boreskov Institute of Catalysis Novisibirsk  200x200x50 mm tiles – the largest ever  n=1.03 ; gives  /K separation up to ~10 GeV/c  Exceptional clarity C ~ 0.005  m 4 cm -1 [I/I 0 = A exp –(Ct/ 4 ) for thickness t]  Excellent homogeneity  (n-1)/(n-1) <1%  Tiles have undergone extensive ageing studies The RICH1 Aerogel Radiator Test installation into RICH1  See talk by Tito Bellunato and poster by Davide Perego

11. 11 RICH 2007 15-20 October, Trieste N. Harnew RICH2 schematic : “horizontal” geometry 8m Magnetic Shields protect the HPD planes Flat Mirrors each made from 20 square glass segments HPD planes of 9 by 16 HPDs Gas Enclosure Contains CF 4 gas radiator and the optical system Spherical Mirrors each made from 21 glass hexagonal segments RICH2 entrance / exit windows carbon fibre and foam sandwich

12. 12 RICH 2007 15-20 October, Trieste N. Harnew RICH2 to the pit-Nov 2005 Mirrors aligned to 150  rad before move After move, mirror movement ~100  rad n Stability & alignment verified. No need to re-align in situ cf. RICH-2 Cherenkov angle resolution ~ 700  rad

13. 13 RICH 2007 15-20 October, Trieste N. Harnew Pixel Hybrid Photon Detectors  Pixel HPDs developed in collaboration with industry (Photonis-DEP lead partner)  Combines vacuum technology with silicon pixel readout ( Quartz window with S20 photocathode).  484 HPDs occupy a total area of 3.3m 2 with 2.5 x 2.5 mm granularity  Factor 5 demagnification @ 20kV.  Operates at the LHC bunch crossing frequency (40MHz)  Encapsulated 32x32 pixel silicon sensor Bump-bonded binary readout chip  200-600 nm wavelength coverage

14. 14 RICH 2007 15-20 October, Trieste N. Harnew HPD qualification  Two Photon Detector Test Facilities (PDTFs) have qualified all 550 HPDs produced by Photonis/DEP.  98% of tubes have passed the selection criteria.  Excellent response, QE, dark counts, ion feedback etc. See talk by Stephan Eisenhardt

15. 15 RICH 2007 15-20 October, Trieste N. Harnew The HPD readout chain  All HPDs arranged in columns with ancillary front- end electronics  LV & HV boards power the HPDs  Level-0 boards pass triggered data to the Level-1 off-detector board via an ~100m optical link  Level-1 off-detector receives and zero-suppresses the data and passes to the DAQ HPD column assembly

16. 16 RICH 2007 15-20 October, Trieste N. Harnew RICH2 Commissioning Laser photon source. Hit map of 2.4M channels. RICH2 is complete and running 10kV applied. See talk by Carmelo D’Ambrosio n Most of columns have been up to 20kV. Operating RICH2 has now become a routine and safe task. n 10 failed HPDs disconnected (out of 288) – these will be replaced n The detector control/safety systems (DCS and DSS) are operational n RICH2 is ready for global commissioning.

17. 17 RICH 2007 15-20 October, Trieste N. Harnew Detector control system in place HPD box temperature HPD box humidity Cooling pressure over 60 days Light level See talk by Mario Sannino University Genoa

18. 18 RICH 2007 15-20 October, Trieste N. Harnew RICH calibration procedures in place n Calibration & alignment systems use projected test patterns:  Corrections to HPD trajectories for magnetic field.  RICH alignment monitoring. n Calibration & alignment also with tracks (data):  Alignment with tracks.  Refractive index monitoring.  Cherenkov angle resolution from isolated rings.  Particle ID calibration with D*’s See talk by Antonis Papanestis Test pattern with B=0 B=0 and B=30G

19. 19 RICH 2007 15-20 October, Trieste N. Harnew RICH performance (testbeam) Pixel map of a C 4 F 10 ring integrated with ~50k events over 3 HPDs (preliminary)  Performance of the RICH system has been verified in a 80 GeV/c charged particle beam at CERN SPS. C 4 F 10 ~1m radiator length.  Realistic 25 ns beam structure  Final RICH hardware and DAQ  RICH specifications for photon yield and θ c resolution have been verified. C 4 F 10 run See talk by Sean Brisbane

20. 20 RICH 2007 15-20 October, Trieste N. Harnew PID Performance  Ring finding - The algorithm uses tracks, and performs a global likelihood fit to particle hypotheses across both RICH detectors.   – K separation - Excellent efficiency and low mis-ID rate See talk by Claus Buszello

21. 21 RICH 2007 15-20 October, Trieste N. Harnew Summary and prospects  LHCb RICH has excellent particle ID - crucial for the B physics programme of LHCb  RICH1 installation almost complete  Ready for commissioning at end of year  Innovative carbon fibre mirror and aerogel technology  RICH2 is almost commissioned  Ready for global commissioning  Hybrid Photon Detectors provide excellent single photon sensitivity. Performance is excellent LHCb expects its first physics data in 2008, with stable running in 2009. We look forward to data-taking with a completed RICH system !

22. 22 RICH 2007 15-20 October, Trieste N. Harnew Spare slides

23. 23 RICH 2007 15-20 October, Trieste N. Harnew RICH Performance AerogelC 4 F 10 CF 4 Chromatic2.40.90.5 Emission Point 0.40.80.4 Pixel0.5 0.2 Track0.5 0.2 Overall2.51.40.7 Single Cherenkov photon angle resolution (mrad) number of photoelectrons AerogelC 4 F 10 CF 4 5.324.018.4 Chromatic Uncertainty The uncertainty due to the dependence of the refractive index on the wavelength of the photon Emission point Error The uncertainty due to the assumption the photon was emitted at the centre of the track Pixel Uncertainty The uncertainty due to the limited resolution of the pixel detectors Tracking Uncertainty The uncertainty due to the limited accuracy of the tracking stations Combining Uncertainty The CU, EPE and PE are independent but the TU is not and so does not reduce with higher statistics

24. 24 RICH 2007 15-20 October, Trieste N. Harnew HPD test results

25. 25 RICH 2007 15-20 October, Trieste N. Harnew Magnetic Distortion calibration  B┴B┴ B║B║  Magnetic fields distort the electron trajectories of the HPDs.  We should expect significant distortions in the LHCb RICHes (max 24 Gauss in RICH1).  Tubes are individually shielded in mumetal cylinders to mitigate these effects.  Below: RICH2 projection system AxialTransverse

26. 26 RICH 2007 15-20 October, Trieste N. Harnew LHC “approved” schedule - Aug 2007