1. A RICH with Aerogel for a hadron machine On behalf of the LHCb RICH group Some results and considerations on: Cerenkov angle resolution from aerogel Index of refraction homogeneity in an aerogel tile And of Budker and Boreskov Institutes of Novosibirsk

2. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi The RICH of LHCb p (GeV/c) radiatorRefractive index 2 - 10Aerogel 1.030 10 – 60 C 4 F 10 1.0014 60 - 160 CF 4 1.0005 Momentum The RICH-1

3. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi A RICH with aerogel for an hadron machine is a big challenge with respect to experiments like: HERMES (  C resolution ~ 9 mrad measured) or BELLE (RICH upgrade  θ C resolution ~ 12 mrad expected) Because of: exposed to high radiation dose very high multeplicity and background it is mandatory : photoelectron multeplicity as high as possible angular resolution as small as possible A RICH with aerogel

4. RICH-1 (aerogel+C 4 F 10 ) RICH-2 (CF 4 ) (Vassily Kandinsky)

5. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi AEROGEL as Čerenkov radiator very light, solid quartz-like structure SiO 2 low density around 0.15 g/cm 3 refractive index n  = 1 + 0.21  transparent in the visible region can be hygroscopic or hydrophobic LHCb choice T = A e (- C t /  4 ) A is the long  transmittance and C is the clarity coefficient Photon transmission is described by : where

6. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi C = 0.0045-0.0065  m 4 cm -1 T = 35% for 4 cm tile at 400 nm Boreskov Institute of Catalysis (Novosibirsk) AEROGEL Index of refraction: n = 1.03066 n = 1.02982 10 x 10 x 4 cm 3 tile (2002) 4 cm 8 cm

7. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi 1 big tile 11.6 x 11.6 x 5.5 cm 3 successfully produced in 2003 n=1.026 at =400 nm AEROGEL C = 0.0057  m 4 cm -1 T = 30% for 5 cm at 400 nm

8. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi AEROGEL as Čerenkov radiator Tiles 20.0 x 20.0 x 5.1 cm 3 successfully produced in 2004 n=1.029-1.031 at =400 nm C = 0.0060  m 4 cm -1 T = 30% at 400 nm

9. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi  ’s from 60 Co (ISS) humidity absorption protons from IRRAD-1 (CERN-PS) C and T measurements after baking the tile neutrons from IRRAD-2 (CERN-PS) Aerogel ageing tests

10. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi Contributions to the angular resolution  /  : Č angle resolution Pixel  C /  C ~ d/4R (d pixel size, R mirror focal distance) chromatic dispersion  C /  C ~ ½ [  n /(n-1)] ( depends on the n n(λ) functional behaviour e.g. Sellmeier) Emission point  C /  C ~ t sinθ C cosθ C / L√12 (t rad.thickness, L distance to PD) Index of refraction  C /  C  ½ [  (n-1)/(n-1)] Tracking  C /  C depends on precision of tracking system (+ alignment of optics, optics distortion,…)

11. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi The RICH of LHCb Aerogel properties Čerenkov Angle precision Photoelectron yield L [cm] n  c max [mrad] p thres (  ) [GeV/c] p thres (K) [GeV/c] 5 1.030 242 0.6 2.0   chrom [mrad]   pixel   emiss [mrad]   track [mrad]   total [mrad] N p.e. 2.1 0.6 0.3 1.4 2.6 6.8

12. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi Measurements of   with beams To measure  , separation power, N p.e. use: Beam from CERN-PS 2 – 10 GeV/c (  p/p=1%) Negative :  - Positive :  + /protons (50 – 70%) Photodetectors: 4 pad-HPDs produced at CERN 3 pixel-HPD produced by DEP (final PD of LHCb) Beam:

13. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi AEROGEL test beam with 4 pad-HPD Published in NIMA 519(2004) 493

14. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi AEROGEL test beam Aerogel thickness with filter (0.3 mm )  C   no filter  C   4 cm 247.1 5.0 246.8 3.1 250.0 5.4 248.7 4.0 8 cm 245.4 4.8 243.7 3.0 246.8 5.8 245.0 3.9 4 cm 6.3 ± 0.7 7.4 ± 0.8 9.7 ± 1.0 11.5 ± 1.2 8 cm 9.4 ± 1.0 10.1 ± 1.1 12.2± 1.3 14.7 ±1.6 RESULTS with 4 pad-HPD  C and   N p.e. DATA and MONTECARLO Published in NIMA 519(2004) 493

15. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi Aerogel Mirror AEROGEL test beam with 3 pixel-HPD

16. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi AEROGEL test beam DATA and MONTECARLO RESULTS with 3 pixel-HPD Aerogel thickness with filter  C   no filter  C   4 cm 237.1 2.8 238.1 2.4 238.9 3.3 239.1 2.8 N p.e. 9.2 ± 0.8 9.4 ± 1.1 12.8 ± 1.0 14.4 ± 1.6 (preliminary)

17. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi Measurements of Čerenkov angle resolution   c from test beam data are typically about 30% larger than expected Must understand this disagreement (aerogel description in MC, PD behaviour,…???..) Another possible contribution to   C is a dishomogeneity of n inside an aerogel tile Measure it with 2 methods Laser beam (lab) electron beam (Č effect) 500 MeV e - at BTF Č angle resolution in aerogel

18. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi Measurements performed on a 10×10×4.2 cm 3 tile with n=1.031 at L=75.8 cm  n with laser beam   ~0.35 mrad  n ~0.8∙10 -4 =543.5 nm

19. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi Aerogel CCD camera laser

20. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi  n with laser beam  (n-1)/(n-1)~1.3%  n ≈ 4.6∙10 -4   ≈ 1.8 mrad Result for this tile:

21. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi A erogel P hotographic A nalysis by Ch erenkov E mission  n with e - beam 500 MeV electron beam at the DA  NE Beam Test Facility (LNF – Frascati) B&W photographic films as photodetectors

22. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi  n with e - beam Film Mirror Aerogel Scan of the aerogel tile:

23. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi Mirror Aerogel e - beam Film APACHE Aerogel ring N 2 ring Cherenkov ring width dominated by chromaticity n=n(l)  (n-1)/(n-1)=1% →  (θ C )=1.17 mrad

24. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi Aerogel ring N 2 ring Hit-by-hit retracking algorithm to build the distribution of the reconstructed  C angle Resolution: ~0.3 mrad  n with laser beam DATA

25. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi  n with laser beam Result for this tile:   ≈ 1.14 mrad  (n-1)/(n-1) < 1% Nitrogen Aerogel

26. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi Summary and plans RICH with aerogel is an essential detector component for b-physics program of LHCb (p/K/p separation in the 2-10 GeV range) Aerogel for a RICH at LHC is a big challenge: needs excellent optical quality to perform an excellent angular resolution and photoelectron yield Measured angular resolution not yet completely described by MonteCarlo simulation aerogel simulation needs to be improved to understand fully the intrinsic angular resolution homogeneity in n across a tile must be known

27. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi Bern Museum of Art exhibition ‘La legerete de l’art’ (31 july – 17 august 2003) (by Veronica Jenssen)

28. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi Spare slides

29. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi The LHCb detector Forward single-arm spectrometer RICH 1 RICH 2 YZ view

30. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi

31. RICH2004 30 Nov. – 5 Dec. 2004 Clara Matteuzzi