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“Tests of a proximity focusing RICH with aerogel as radiator”

This study presents tests and results of a proximity focusing RICH with aerogel as a radiator for the Belle Aerogel-RICH R&D group. It covers aerogel properties, transmission, index uniformity, and proximity focusing benefits for particle separation and imaging. The study discusses the development of KEK aerogel and the potential applications in collider experiments for improved particle identification.

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“Tests of a proximity focusing RICH with aerogel as radiator”

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  1. “Tests of a proximity focusing RICH with aerogel as radiator” for Belle Aerogel-RICH R&D group Toru Iijima / Nagoya University Iijima@hepl.phys.nagoya-u.ac.jp • Introduction for aerogel + proximity focusing • Simulation • Results from the 1st beam test • Discussion • Summary

  2. Collaborators Belle Aerogel-RICH R&D group; I.Adachi2, I. Bizjak5, A. Gorisek5, T. Iijima3, M. Iwamoto1, S. Korpar5,8, P. Krizan7,5, R. Pestotnik5, M. Staric5, A. Stanovnik5,6, T. Sumiyoshi4, K. Suzuki2 and T. Tabata1 1 Chiba University, Chiba, Japan 2 High Energy Accelerator Research Organization (KEK), Japan 3Physics Department, Nagoya University, Nagoya, Japan 4Physics Department, Tokyo Metropolitan University, Tokyo, Japan 5 Jozef Stefan Institute, Ljubljana, Slovenia 6 Faculty of Electrical Engineering, University of Ljubljana, Slovenia 7 Faculty of Mathematics and Physics, University of Ljubljana, Slovenia 8 Faculty of Chemistry and Chemical Engineering, University of Maribor, Slovenia “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  3. Introduction • Silica aerogels… • Collidal form of SiO2 • r=0.1g/cm3 • Prosity ~ 95% (n=1.03) • n=1.006~1.06 ⇒useful for p/K separation in GeV region • Applied in many particle/nuclear physics exp’s. But, mostly used in threshold mode (before). • Limitation for imaging • Rayleigh scattering • Cracks Established technique Simple & reliable Limited momentum coverage Kaon ID in veto mode “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  4. KEK Aerogel • Development in 90’s for Belle-ACC at the KEK B factory. • New single-step production method developed in collaboration with Matsushita E.W.Co • Good optical quality: • Transmission • Index uniformity • Long term stability • Hydrophobicity • Radiation hardness Improved optical quality of aerogels →Break through for imaging (“Aerogel-RICH”). “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  5. Transmission of aerogels • Almost 3 times better transmission (dominated by Rayleigh scattering) “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  6. Index uniformity • Dn/(n-1) = ±3% (FWHM) in Belle-ACC experience “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  7. Ring viewed by IIT Yes, rings are there ! “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  8. n=1.47 n=1.03 RICH w/ aerogel radiator • Larger Dqc between two particle species • Wider PID coverage ⇔ threshold • p/K separation @ higher momentum (~10GeV/c?) • m/p separation @ low momentum (<1GeV/c) Note: p/K sep.(5GeV/c) ~ m/p sep.(1GeV/c) • Compact ring size q ~ 13°for n = 1.03 / b = 1 • Small material thickness • Photodetection in the visible region Short wave length component strongly suppressed by Raｙleigh scattering. K-p p-K m-p “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  9. Proximity Focusing ? • Mirror focusing • HERMES/LHC-B (open geometry exp.) • Thick aerogel ⇒ Easier to obtain enough light yield. • Proximity focusing • Suitable for collider exp. • Aerogel must be thin enough not to deteriorate the angle resolution. ⇒ Light yield ? • Never been considered well by other exp’s. Talk by M.Buenerd (AMS) Maybe difficult but CHALLENGING ⇒Our R&D “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  10. Possibility at Future Belle • Present Belle PID system • Combination of dE/dx + ToF + ACC • KID eff.=88%/fake=8.5%. • “Particle ID Holes” • EACC works only for tagging • e/m-p separation at low momentum • Proximity focusing aerogel-RICH for the endcap to cover give p/K sep.in 0.8<p(GeV/c)<4.5 ※photodetection is hard for Barrel photoelectrons must drift perpendicular to the B filed axis. • TOP counter for Barrel ⇒ Talk by T.Ohshima “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  11. R&D History • By 2000: Some preliminary studies Imaging test with IIT / Photodetection / Simulation … busy years for Belle-ACC though,… • March 2001: “Proximity focusing aerogel-RICH” introduced as a possible Belle PID upgrade option by T.I. J.Stefan institute joined the R&D Discussion for Super-KEKB/Belle • June‐Oct. 2001: Cosmic ray test at IJS. • Nov.‐Dec. 2001: Beam test at KEK 12 GeV-PS “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  12. Simulation Ingredients • Production of Cherenkov photons：F-T formula • Chromatic dispersion：Scaled from fused silica • Rayleigh scattering： Mean free path based on transmission data (with correction of finite acceptance of photospectrometer) • Photodetection： Bialkari photocathode (QE = 25% at 400nm) Pad size : 5mm/10mm “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  13. Simulation Result (I) • Simulated Npe for unscattered photons. • Normal incidence • Assume 100% geometrical acceptance for photodetection • Higher n is preferred to have enough light yield for pions at 0.8 GeV/c. ⇔Lower n gives better separation at high momentum (next slide). “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  14. 4GeV/c p K 5.7s separation Cherenkov angle Simulation Result (II) • Simulation indicates: • Npe>12 possible for light velocity particles • N=1.030 gives better separation, but light yield at around threshold (p~0.8GeV/c) may be critical. ⇒Optimal n ~1.05 • Separation @ 4GeV/c > 5s possible even with 10mm read-out pad. ⇒Need verification with experiment. “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  15. 2cm thick n=1.03/1.05/1.07 p = 0.5~4.0Gev/c p±, p (Gas C to eliminate e) Incident angle 0 ~ 30 deg. 1st Beam Test • Nov.25~Dec.2 @ KEK-PS, p2 beam line Aerogel sample “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  16. Photodetection • 6×6 Multi-anode PMT array based on • Hamamatsu R5900-M16 • 36% photocathod coverage: • □18mm / 30mm pitch • Two read-out configuration • Coarse granularity: • Every 4 pads grouped together (144ch) • ⇒optimum for light yield measurement • Fine granularity: • only 1/3 sector connected to TDC (192ch) • ⇒optimum for angular reso. measurement Coarse granularity Fine granularity “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  17. Observed Ring Image • Coarse granularity, 3GeV/c p- • n=1.029 (2cm thick) Ring expected from tracking Hit due to beam 2D hit distribution w.r.t beam Typical hits / event “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  18. Data @ p= 0.5GeV/c • e-, m-, p- at low momentum with beam line polarity at negative electron veto by gas C “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  19. Typical distribution • Ndet & sq are obtained by fitting the q distribution. • Gaussian + background  Ns • Ndet = Ns/#event • Also checked Ndet by counting hits in ±3s window around the peak. • sq is the single photon angular resolution. Counting in ±3s window Gaussian+background ＊Poisson based on 0 hit bin Ndet = Ns/#event “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  20. C (in PMT acceptance) C (whole ring) fcorr = Detected photon / event • Ndet = 2.6/2.7 for n=1.029/1.050 samples (2cm thick). • Note: n=1.050 has worse transmission • Correction by PMT array acceptance applied (event-by-event). 2.8cm Novosibirsk 2+2cm coarse 2cm fine 2cm coarse “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  21. d Angular resolution • Fine granularity (4.5mm pad) ⇒sq ~ 10mrad at d = 20cm, 2cm thick, n=1.029/1.050. • d: distance between radiator and photodetector varied depending on index: d=29cm (1.029), 21cm(1.050), 17cm(1.070) • Right figure shows the results when normalized to d = 20cm. Normalized at d=20cm 2cm fine gran. “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  22. Momentum dependence • Momentum dependence is as expected. • Lines in figures are expected dependence fit to the data points. • Effect of multiple scattering at low momentum (sq) sq (not normalized by d) Ndet/ring “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  23. Incident angle dependence • Almost no dependence on incident angle. Ndet/ring sq (not normalized by d) “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  24. Discussion • Comparison to expectation (2cm, 3GeV/c pions) Assume: 36% effective area 70% correction eff. • Importatnt R&D issues: • Improvement of aerogel quality • Better transmission • Improvement of photodetection • Good effective area (36%  70%) • Good efficiency for single photon “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  25. Novosibirsk sample (48mm) Large potential to improve Improvement of aerogels • Significant increase in Ndet with n=1.050 Novosibirsk sample. • Ndet = 4.6 (28mmt) 2.7 (20mmt) w/ KEK • 70% increase (40% increase when thickness difference accounted). • We aim at improving the quality at n~1.05 by revisiting; • Production method/procedure • Precursor material • Solvent • Other R&D issues • Size • Flatness etc. Talk by A.F.Danilyuk “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  26. Photodetection • Flat Panel PMT array for R&D • Newly developed 8 ×8 multi-anode PMT by HPK. • Effective area = □49mm for □51.7mm package (90% coverage) • Single p.e. peak is observable. • Further performance studies and better understanding of the detector behavior. • Optimization of design • In real application in 1.5T magnetic field at Belle, ⇒Proximity focusing HPD with good effective area Flat Panel HPD/HAPD? “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  27. Summary • Improved optical quality of aerogels in 90’s opened the window for aerogel-RICH. • We have tested possibility of proximity focusing aerogel-RICH with beam • Angular resolution < 10mrad with ~5mm pad. • Light yield ~ 2.7 with photodetection efficiency of 25% (=36×70%). • ⇒ Good starting point; • Results are reasonable and understood. • They clarify the R&D targets. • Further improvement of aerogel quality (n ~ 1.05) • Proximity focusing H(A)PD with good effective area. ×(1.5~2.0) ×>2 Our hope for improvement factor. If achieved, K/p separation > 6s (@ 4GeV/c) possible “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  28. Thank you !!! “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  29. Backup Slides “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  30. Lens System Optionally used in the beam test. “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  31. Physics Requirement • Importance of K/p separation remains unchanged also at the Super-Belle. • Flavor tagging (p<2 GeV/c) • For any CPV measurement in neutral B. • Two-body decays (1.5<p<4GeV/c) • B→pp/Kp, B→rp(ppp) / Kpp • B→DK/Dp • Others: h’p/h’K etc. • Increased demand at the Super KEKB/Belle • b→dg/b→sg (required reduction ~50?) Good separation in inclusive measurements (multiple tracks) • Full reconstruction tag (efficiency/purity) • How about t / charm ? • ++ low momentum e/m-p separation (< 1 GeV/c) • B→K(*)ll (b →sll) (especially in m channel) Good K/p < 5 GeV/c ⇒ good m/p < 1 GeV/c Large impact of improved PID “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  32. Present Belle-PID Combination of dE/dx + ToF + ACC • Performance • eff.=88%/fake=8.5%. • Concerns: • Background immunity • TOF dead time: O(10%) • Material thickness • Radiation hardness • “Particle ID Holes” • EACC works only for tagging • e/m-p separation at low momentum ⇒Points of improvement @ upgrade “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  33. K*+g r g K+p+p-p0g p+p+p-p0g (): Endcap as it is. K/p-ID Impact in b→dg/b→sg • B+ → r g / K*+g (p+p-g /K+p-g) • B0 → p+p+p-p0g / K+p+p-p0g • Conditions: • Br(sg) = 20×Br(dg) • Present eff/fake from data (open histograms) • Improved eff/fake = 0.975/0.025 ~ 4s separation of two Gaussian (hatched histograms) PID w/ good eff/fake and hermeticity is important “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  34. Lepton/p-ID Impact in b→sll • Forward-backward asymmetry (AFB) • Need to measure AFB as a function of Mll May flip sign below and above 1.5GeV However, • In Kmm channel, Mll<1.5GeV is difficult because (almost) no m/p separation. • Present MUID + 97.5% @ p<1GeV/c by Cherenkov ⇒ ×2 events in Mll < 1 GeV ⇒ ×1.5 events in 1 < Mll < 2 GeV A good Cherenkov detector will give significantly earlier finding of AFB and test of the sign flip. “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  35. ‘Flat panel HPD’ Concept Photon counting w/ hybrid PD (typical spectrum) “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

  36. Dual Radiator Scheme • Interesting option, if aerogel transmission is improved. • Light yield can be increased without deteriorating the angular resolution. • Need study effectiveness with simulation “Tests of a proximity focusing RICH with aerogel as radiator”, by Toru Iijima, June 8, 2002

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