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

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