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Design and Performance of BTeV RICH Detector

This study presents the design and expected performance of the BTeV RICH detector, which aims to improve measurements of CKM angles and search for rare and beyond the Standard Model decays in B physics. The detector features a gas radiator for momentum coverage above 9.5 GeV/c and a liquid radiator for momentum coverage below 9.5 GeV/c. The detector utilizes spherical mirrors to focus photons onto photomultiplier tubes (PMTs) and has a segmented design to achieve a total uncertainty per photon below 1 mrad.

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Design and Performance of BTeV RICH Detector

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  1. Design of the BTeV RICH and its Expected Performance Steven Bluskforthe BTeV Collaboration

  2. Belarussian State-D .Drobychev, A. Lobko, A. Lopatrik, R. Zouversky UC Davis - J. Link, P. Yager Univ. of Colorado at Boulder J. Cumalat Fermi National Lab J. Appel, E. Barsotti, CN Brown, J. Butler, H. Cheung, G. Chiodini, D. Christian, S. Cihangir, I. Gaines, P. Garbincius, L. Garren, E. Gottschalk, A. Hahn, G. Jackson, P. Kasper, P. Kasper, R. Kutschke, SW Kwan, P. Lebrun, P. McBride, L. Stutte, M. Votava, M. Wang, J. Yarba Univ. of Florida at Gainesville P. Avery University of Houston K. Lau, B. W. Mayes, J. Pyrlik, V. Rodriguez, S. Subramania Illinois Institute of Technology RA Burnstein, DM Kaplan, LM Lederman, HA Rubin, C. White Univ. of Illinois- M. Haney, D. Kim, M. Selen, J. Wiss The BTeV Collaboration Southern Methodist University - T. Coan SUNY Albany - M. AlamSyracuse University M. Artuso, C. Boulahouache, O. Dorjkhaidav K. Khroustalev, R.Mountain, R. Nandakumar, T. Skwarnicki, S. Stone, JC Wang, H. Zhao Univ. of TennesseeK. Cho, T. Handler, R. Mitchell Tufts Univ.– A.Napier Vanderbilt University W. Johns, P. Sheldon, K. Stenson, E. Vaandering, M. Webster Wayne State UniversityG. Bonvicini, D. Cinabro University of WisconsinM. Sheaff Yale University J. Slaughter York UniversityS. Menary Indiana University RW Gardner, DR Rust Univ. of Insubria in Como- P. Ratcliffe, M. Rovere INFN - Frascati- M. Bertani, L. Benussi, S. Bianco, M. Caponero, F. Fabri, F. Felli, M. Giardoni, A. La Monaca, E. Pace, M. Pallota, A. Paolozzi, A. Scicutelli INFN - Milano – G. Alimonti, M. Citterio, P. D’Angelo, S. Magni, D. Menasce, L. Moroni, D. Pedrini, M. Pirola, S. Sala, L. Uplegger INFN - Pavia - G. Boca, G. Cossail, E. Degliantoni, PF Manfredi, M. Manghisoni, M. Marengo, L. Ratti, V. Re, V. Speziali, G. Traversi INFN - Torino N. Cartiglia, R. Cester, F. Marchetto, R. Mussa, N. Pastrone IHEP Protvino, Russia A. Derevschikov, Y. Goncharenko, V. Khodyrev, A. Meschanin, L. Nogach, K. Shestermanov, L. Soloviev, A. Vasiliev University of Iowa C. Newsom, R. Braunger University of MinnesotaV. V. Frolov, Y. Kubota, R. Poling, A. Smith Nanjing Univ. (China) T. Y. Chen, D. Gao, S. Du, M. Qi, BP. Zhang, JW Zhao Ohio State University K. Honscheid, & H. KaganUniv. of Pennsylvania W. Selove Univ. of Puerto Rico A. Lopez, & W. Xiong Univ. of Science & Tech. of China - G. Datao, L. Hao, Ge Jin, L. Tiankuan, T. Yang, XQ Yu Shandong Univ. (China)CF Feng, Yu Fu, Mao He, JY Li, L. Xue, N. Zhang, & XY Zhang

  3. Physics of BTeV • BTeV will vastly improve the constraints on the CKM anglesby making precision measurements of both the sides andthe angles a, b, g.  over-constrain (r,h). • Measurements and searches for rare and SM forbiddendecays “Beyond the SM” Physics. • B factories will provide valuable input on sin(2b) and Vub,but they cannot compete with a hadron collider on measuringa, g, and searches for new physics (even by 2007). - They don’t produce BS- s(bb) is ~10,000X larger at the Tevatron than at U(4S)

  4. The higher momentum b are at larger  b production peaks at large angles with large bb correlation bg Pseudo-rapidity  b production angle b production angle B Production at the Tevatron b cross section ~ 100 mb at 2 TeV 2x1011b’s per 107 sec at L=2x1032 cm-2 s-1.

  5. B Physics Detector “Wish List”

  6. The BTeV Detector

  7. RICH Specifications • Momentum Range of Interest * p > 2-3 GeV for CP tagging * p < 70 GeV  clean separation of 2-body modes: Bpp, Kp, KK. • Minimize material in front of ECAL • Longitudinal space available ~3 meters • Desirable to detect Cerenkov photons in the visible range (minimize chromatic error, less sensitive to contaminants, etc)  Well-suited for a Ring Imaging Cerenkov Detector Tagging kaons in BTeV Acc.

  8. Radiators Large momentum coverage requires a low index of refraction gas radiatorWe chose C4F10 because: * heaviest gas which has high transparency in the visible * wide usage in other HEP expt’s (e.g. Delphi, HERA-B, HERMES, LHC-b). For momenta below 9.5 GeV/c neither K nor P radiate in C4F10 Separate liquid radiator for K/P separation below 9.5 GeV/c

  9. The BTeV RICH C5F12Liquid Radiator Sphericalmirrors • Photons from gasare reflected offmirrors and focused at the HPD plane. • Photons from liquidare directly detected inthe PMTs. C4F10 gasvolume Arrays of163-channelHPDs(~1000 in total) PMT Arrays(~5,000 in total)

  10. Photon Angles Liquid radiator photons are detectedin PMT array. PMT Array Gas radiator photons are detectedin HPD array. Track fromInteraction Gas RadiatorVolume HPD Array LiquidRadiator Mirror

  11. Gas Radiator Gas: C4F10 (n=1.00138): * K/p separation for3 < p <70 GeV * P/K separation for9.5 < p < 70 GeV • Dqc(p-K) ~ 0.43 mrad @ 70 GeV • Must keep s(qC)/trk < 0.13 mrad • N(g) detected ~ 65 (simulation)Total uncertainty per photon must be kept below ~1 mrad. •  Requires ~1.5 mm segmentation •  Well-suited for HPDs No P/K separationbelow ~ 9.5 GeV withgas alone

  12. Detecting Gas Photonswith HPDs g -20 kV • Started with 61-channel HPD that LHC-band DEP developed. • We worked with DEP to develop 163-ch version|which would meet BTeV’s requirements. • Cross-focused onto hexagonal pixels • Signal: ~5000 e- in Silicon. • Readout system is being developed by Syracuse in collaboration with IDE AS Norway. HPD e ~1.5 mm 163 channels * See talk by Ray Mountain

  13. HPD Hexad Mu-metalshield Readout Boardsare mounted here HPD Full HPDArray VA_BTEVASICs(AS&D)

  14. HPD Readout VA_BTeVchip • VA_BTeV ASIC being developed in collaboration with IDE AS Norway(independent from HPD development) • Initial tests indicate that ~500 e- noise level be achieved. • Threshold for each channel is adjustable. • Readout is binary (ON or OFF) • Testing of first prototypes is underwayat Syracuse. Readout Board HPD

  15. More on HPD Readout Number of hit channels in consecutive beam crossingsper 163 channels • Discharge of FE chip requires 2 beam crossings, so a hit channel is dead for the next crossing. • Simulated effect @ L=2x1032 cm-2 s-1. Find <10% loss of photons even in the busiest regions.(Much smaller elsewhere) Y HPD# X HPD#

  16. Liquid Radiator C5F12 (n=1.24): * Extends P/K separation to p<9.5 GeV * Extends K/p separation into the p<3 GeV range • Dqc(p-K) ~ 5.3 mrad @ 9 GeVMust keep s(qC)/trk<1.7 mradN(g) detected ~ 15 (simulation)Total uncertainty per photon must be kept below ~7 mrad • Separate PMT system (3” PMT is acceptable)

  17. Detecting Liquid Photons -- PMTs PMT Layout in BTeV Mu-metalshields • Expect to use 3” tubes. • Shielding necessary ( |B| < 15 G in PMT region) • Expect • s(qgc) ~ 6 mrad, N(g)~15/trk • s(qtrkc) ~ 1.6 mrad 3”

  18. Magnetic Shielding of PMTs PMTs from 4 different manufacturers B Trans. Bmax=15 G Unshielded Shielded 4.0 45.0 B Long. Unshielded Shielded 12.0 45.0

  19. Preliminary Conceptual Tank Design PMT Arrays HPD Arrays

  20. Liquid Radiator Conceptual Design • 1 cm of C5F12 • 3 mm Carbon Fiber front window & 3 mm quartz back window • Split into 5 volumes to reduce pressure. • Structure is reinforced by CF posts • Total Material Budget: X0 ~ 8.7% • Simulations indicate negligible impact on p0 reconstruction since electrons from g conversions are only in a very weak magnetic field.

  21. Progress with Mirrors • Measurements being taken on the test bench of the TA2 group at CERN. • Several mirrors under study • COMPAS: glass, glass+foam back., • CMA: Carbon fiber • Initial tests show that they meet spot size spec. ~60 cm Rcurv=660 cm Work being done byINFN Torino group

  22. Expected Performancefrom Simulations

  23. Efficiency vs Fake Rate Gas Radiator & HPDs • Clean separationof B pp from BKp and BKKFor example: • e(B pp): 80%Kp Rejection ~ 95% KK Rejection > 99% The latter is importantbecause BsKK lieson top of Bpp signal B  pp Simulationw/ 2 minimum biasevents. K+p- K+K-

  24. Low Momentum K/P separation using Liquid Radiator & PMTs K and P cannot be separatedbelow 9.5 GeV/c in gas system.Our simulations showed that we could improve eD2by ~25% for BS and ~10%for B0 using liquid radiator. Mom. < 9 GeV/c

  25. CP side Same-side particle tag K+ BS K+ Away-side tags K–, m-, e-, p, L0,jet charge Recoilingb-hadron Expectations for eD2 Error on CP Asymmetry

  26. Test Beam – May 2003 • ~15 HPDs to coverfull Cerenkov ring • ~100 GeV p beam • Will measure: * resolution on Cerenkov angle * photon yield • We’ll also scan themirror to checksensitivity • Construction underway. HPD Enclosure Front Entrance Window Mirror Assembly Concrete Support Blocks

  27. Summary • The BTeV RICH uses : • gas system: C4F10 gas and HPDs, and • liquid system: C5F12 and PMTs to achieve excellent p/K/P separation for all relevant momenta less than 70 GeV/c. • Recent addition of the liquid radiator system will improve eD2 for CP tag by ~25% for BS and ~10% for B0. • Initial tests of HPDs/PMTs look encouraging (see talk by R. Mountain) • Test beam next year to validate detector design and simulations.

  28. Low mult. event Why did we punt on Aerogel? • Both gas & aerogel photons were detected in the HPDs • After removing photons which were consistent with more than 1 track, aerogelprovided essentially no K/P separation • The aerogel rings have too few photonsto compete with the bright gas rings High mult. event

  29. Alternate solution fordetecting gas photons(MA-PMT16) • Larger active region than 1st gen.  lens system not required • Viable backup to HPDs  slightly worse position resolution.. • Currently being tested at Syracuse.

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