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

RICH Nov. – 5 Dec Clara Matteuzzi The RICH of LHCb p (GeV/c) radiatorRefractive index Aerogel – 60 C 4 F CF Momentum The RICH-1

RICH Nov. – 5 Dec 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

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

RICH Nov. – 5 Dec 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  =  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

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

RICH Nov. – 5 Dec 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 =  m 4 cm -1 T = 30% for 5 cm at 400 nm

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

RICH Nov. – 5 Dec 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

RICH Nov. – 5 Dec 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,…)

RICH Nov. – 5 Dec 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]   chrom [mrad]   pixel   emiss [mrad]   track [mrad]   total [mrad] N p.e

RICH Nov. – 5 Dec 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:

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

RICH Nov. – 5 Dec Clara Matteuzzi AEROGEL test beam Aerogel thickness with filter (0.3 mm )  C   no filter  C   4 cm cm cm 6.3 ± ± ± ± cm 9.4 ± ± ± ±1.6 RESULTS with 4 pad-HPD  C and   N p.e. DATA and MONTECARLO Published in NIMA 519(2004) 493

RICH Nov. – 5 Dec Clara Matteuzzi Aerogel Mirror AEROGEL test beam with 3 pixel-HPD

RICH Nov. – 5 Dec Clara Matteuzzi AEROGEL test beam DATA and MONTECARLO RESULTS with 3 pixel-HPD Aerogel thickness with filter  C   no filter  C   4 cm N p.e. 9.2 ± ± ± ± 1.6 (preliminary)

RICH Nov. – 5 Dec 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

RICH Nov. – 5 Dec 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

RICH Nov. – 5 Dec Clara Matteuzzi Aerogel CCD camera laser

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

RICH Nov. – 5 Dec 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

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

RICH Nov. – 5 Dec 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

RICH Nov. – 5 Dec 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

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

RICH Nov. – 5 Dec 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

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

RICH Nov. – 5 Dec Clara Matteuzzi Spare slides

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

RICH Nov. – 5 Dec Clara Matteuzzi

RICH Nov. – 5 Dec Clara Matteuzzi