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BTeV – A Dedicated B Physics Experiment at the Tevatron Collider

BTeV – A Dedicated B Physics Experiment at the Tevatron Collider. Klaus Honscheid The Ohio State University DPF 2002, May 24, 2001. Belarussian State- D .Drobychev, A. Lobko, A. Lopatrik, R. Zouversky UC Davis - P. Yager Univ. of Colorado- J. Cumalat Fermi National Lab

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BTeV – A Dedicated B Physics Experiment at the Tevatron Collider

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  1. BTeV – A Dedicated B Physics Experiment at the Tevatron Collider Klaus Honscheid The Ohio State University DPF 2002, May 24, 2001

  2. Belarussian State- D .Drobychev, A. Lobko, A. Lopatrik, R. Zouversky UC Davis - P. Yager Univ. of Colorado-J. Cumalat Fermi National Lab J. Appel, E. Barsotti, C. N. Brown , J. Butler, H. Cheung, G. Chiodini, D. Christian, S. Cihangir, R. Coluucia, I. Gaines, P. Garbincius, L. Garren, E. Gottschalk, A. Hahn, P. Kasper, P. Kasper, R. Kutschke, S. Kwan, P. Lebrun, P. McBride, M. Votava, M. Wang, J. Yarba Univ. of Florida at Gainesville P. Avery University of Houston M. Bukhari, K. Lau, B. W. Mayes, V. Rodriguez, S. Subramania Illinois Institute of Technology R. A. Burnstein, D. M. Kaplan, L. M. Lederman, H. A. Rubin, C. White BTeV Collaboration Univ. of Illinois- M. Haney, D. Kim, M. Selen, J. Wiss Univ. of Insubria in Como- P. Ratcliffe, M. Rovere INFN - Frascati- M. Bertani, L. Benussi, S. Bianco, M. Caponero, F. Fabbri, F. Felli, M. Giardoni, A. La Monaca, E. Pace, M. Pallotta, A. Paolozzi INFN - Milano - G. Alimonti, P. D’Angelo, L. Edera, S. Magni, D. Menasce, L. Moroni, D. Pedrini, S.Sala, L. Uplegger INFN - Pavia - G. Boca, G. Liguori, & P. Torre INFN - Torino – R. Arcidiacono, S. Argiro, S. Bagnasco, N. Cartiglia, R. Cester, F. Marchetto, E. Menichetti, R. Mussa, N. Pastrone IHEP Protvino, Russia A. Derevschikov, Y. Goncharenko, V. Khodyrev, V. Kravtsov, A. Meschanin, V. Mochalov, Southern Methodist University - T. Coan SUNY Albany - M. AlamSyracuse University M. Artuso, S. Blusk, C. Boulahouache, O. Dorjkhaidav, K. Khroustalev, R.Mountain, N. Raja, T. Skwarnicki, S. Stone, J. C. Wang Univ. of Tennessee T. Handler, R. Mitchell Vanderbilt University W. Johns, P. Sheldon, K. Stenson, E. Vaandering, & M. Webster Univ. of Virginia: M. Arenton, S. Conetti, B. Cox, A. Ledovskoy Wayne State University G. Bonvicini, & D. Cinabro, A. Shreiner University of Wisconsin M. Sheaff York University S. Menary D. Morozov, L. Nogach, K. Shestermanov, L. Soloviev, A. Uzunian, 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, B. P. Zhang, Z. Xi Zhang, J. W. Zhao Ohio State University K. Honscheid, & H. Kagan Univ. of Pennsylvania W. Selove Univ. of Puerto Rico A. Lopez, & W. Xiong Univ. of Science & Tech. of China - G. Datao, L. Hao, Ge Jin, T. Yang, & X. Q. Yu Shandong Univ. (China)- C. F. Feng, Yu Fu, Mao He, J. Y. Li, L. Xue, N. Zhang, & X. Y. Zhang

  3. CKM, CP and all that From Hocker et al: Current constraints on bd CKM triangle From Peskin: Many independent checks are needed Magnitudes Bd, BsMixing Phases

  4. Some crucial measurements

  5. The Opportunity Lot’s of b’s(a few times 1011 b-pairs per year at the Tevatron) “Broadband, High Luminosity B Factory”(Bd, Bu, Bs, b-baryon, and Bc ) Tevatron luminosity will increase to at least 5x1032 Cross sections at the LHC will be 5 times larger Because you are colliding gluons, it is intrinsically asymmetric so time evolution studies are possible (and integrated asymmetries are nonzero) The Challenge Lot’s of background(S/N 1:500 to 1:1000) Complicated underlying event No stringent kinematic constraints that one has at an e+e- machine Multiple interactions B Physics at Hadron Colliders These lead to questions about the triggering, tagging, and reconstruction efficiency and the background rejection that can be achieved at a hadron collider

  6. The Tevatron as a b & c source property Value 2 x 1032 100 mb 4 x 1011 10-3 >500 mb 132 ns sz = 10-20 cm sx ~ sy ~ 50 mm <2.0> Luminosity b cross-section # of b’s per 107 sec b fraction c cross-section Bunch Spacing Luminous region length Luminous region width Interactions/crossing

  7. Characteristics of hadronic b production The higher momentum b’s are at larger ’s b production peaks at large angles with large bb correlation Central Detectors Mean bg ~0.75 BTeV BTeV bg b production angle  b production angle

  8. A simulated BTeV Event

  9. The BTeV Spectrometer (revised) • Single Arm • Full Pixel Detector • Full Trigger and DAQ • Reduce costsNew baseline cost ~M$100 • Use extra bandwidth to loosen trigger • Better lepton id Re-gain some performance New baseline performanceabout 70% of original two-arm spectrometer

  10. Key Design Features of BTeV • A dipole magnet (1.6 T) and 2 1 spectrometer arms • A precision vertex detector based on planar pixel arrays • A detached vertex trigger at Level I • High resolution tracking system (straws and silicon strips) • Excellent particle identification based on a Ring Imaging Cerenkov counter. • A lead tungstate electromagnetic calorimeter for photon andp0reconstruction • Excellent identification of muons • A very high capacity data acquisition system which frees us from making excessively specific choices at the trigger level

  11. Pixel Vertex Detector • Reasons for Pixel Detector: • Superior signal to noise • Excellent spatial resolution -- 5-10 microns depending on angle, etc • Very low occupancy • Very fast • Radiation hard • Special features: • It is used directly in the L1 trigger • Pulse height is measured on every channel with a 3 bit FADC • It is inside a dipole and gives a crude standalone momentum

  12. Pixels – Close up of 3/31 stations • 50mm x 400mmpixels - 30 million total • Two pixel planes per station (supported on a single substrate) • Detectors in vacuum • Half planes move together when Tevatron beams are stable. 10 cm

  13. Pixel Readout Chip Test outputs 7.2 mm • Different problem than LHC pixels: • 132 ns crossing time (vs. 25ns)  easier • Very fast readout required  harder • R&D started in 1997 • Two generations of prototype chips • (FPIX0 & FPIX1) have been designed • & tested, with & without sensors, • including a beam test (1999) in • which resolution <9m was demonstrated. • New “deep submicron” radiation • hard design (FPIX2):Three test chip • designs have been produced & tested. • Expect to submit the final design • ~Dec. 2001 8 mm A pixel FPIX1 Readout

  14. Pixel Test Beam Results No change after 33 Mrad (10 years, worst case, BTeV) Analog output of pixel amplifier before and after 33 Mrad irradiation. 0.25m CMOS design verified radiation hard with both g and protons. Track angle (mr)

  15. HDI Sensor Readout chip HDI Wire bonds Sensor (5 readout chips underneath) Pixel detectors are hybrid assemblies • Sensors & readout “bump bonded” to one another. • Readout chip is wire bonded • to a “high density interconnect” • which carries bias voltages, • control signals, and output data. Micrograph of FPIX1: bump bonds are visible

  16. Physics Performance of Pixel Detector Primary-secondary vertex separation Minus generated. s = 138m Distribution in L/s of Reconstructed Bs Mean = 44 t proper (reconstructed) - tproper (generated) s = 46 fs

  17. Three Key Requirements: Reconstruct every beam crossing, run at 7.6 MHz Find primary vertex Find evidence for a B decaying downstream of primary vertex Five Key Ingredients: A vertex detector with excellent spatial resolution, fast readout, and low occupancy A heavily pipelined and parallel processing architecture well suited to tracking and vertex fining Inexpensive processing nodes, optimized for specific tasks within the overall architecture ~3000 CPUs Sufficient memory to buffer the vent data while calculations are carried out ~1 Terabyte A switching and control network to orchestrate the data movement through the system The BTeV Level I Detached Vertex Trigger

  18. p p p p Information available to the L1 vertex trigger

  19. Track segments found by the L1 vertex trigger “entering” track segment “exiting” track segment

  20. Block Diagram of the Level 1 Vertex Trigger PatternRecognition PixelSystem TrackReconstruction VertexReconstruction FPGAAssociativeMemory DSPVertex Farm(1 DSP per crossing) DSPTrack Farm(4 DSPs per crossing) AverageLatency: 0.4 ms AverageLatency: 77 ms AverageLatency: 55 ms Level 1 Vertex Trigger: FPGAs: ~ 500 Track Farm DSPs: ~ 2000 Vertex Farm DSPs: ~ 500 Level 2/3 Trigger 2500 high performance LINUX processors

  21. 74% Pixel Trigger Performance Select number (N) of detached tracks typically pt> 0.5 GeV, N = 2 Select impact parameter (b) w.r.t. primary vertex typically s(b) = 6 Options include cuts on vertex, vertex mass etc. N=1 N=1 N=2 N=2 N=3 N=3 1% N=4 N=4

  22. Trigger Simulation Results • L1 acceptance: 1% 2% • Profile of accepted events • 4 % from b quarks including 50-70% of all “analyzable” b events • 10 % from c quarks • 40 % from s quarks • 45 % pure fakes • L2/L3 acceptance: 4 % • 4000 Hz output rate • 200 Mbytes/s Level 1 Efficiency on Interesting Physics States

  23. BTeV Data Acquisition Overview Trigger/DAQ

  24. Importance of Particle Identification Cherenkov angle vs Mom. P Liquid Gas

  25. Ring Imaging Cherenkov (RICH) • Two identical RICH detectors • Components: • Gaseous Radiator (C4F10 ) • Liquid Radiator (C5F12 ) • Spherical mirrors • Photo-detectors (PM + HPD) • Vessel to contain gas volume Cherenkov photons from Bop+p- and rest of the beam collision

  26. RICH Readout: Hybrid Photodiodes (HPD) • Commercial supplier from Holland (DEP) • A number of prototypes was successfully produced and tested for CMS • New silicon diode customized for BTeV at DEP (163 pixels per HPD) • Challenges: • high voltages (20 kV!) • Signal ~5000e-a need low noise electronics (Viking) • In the hottest region up to 40 channels fire per tube • About 2000 tubes total (cost)

  27. Use of RICH to extend Lepton Identification • While the full detector aperture is 300 mr, the acceptance of the electromagnetic calorimeter and muon detector is only 200mr • The RICH, however, has both electron-pion and muon-pion discrimination at low momentum. The wide angle particles are mostly at low momentum! This gains us a factor of 2.4 for single lepton id and 3.9 if we require both leptons to be identified

  28. Electromagnetic Calorimeter • The main challenges include • Can the detector survive the high radiation environment ? • Can the detector handle the rate and occupancy ? • Can the detector achieve adequate angle and energy resolution ? • BTeV now plans to use a PbWO4 calorimeter • Developed by CMS for use at the LHC • Large granularityBlock size 2.7 x 2.7 x 22 cm3 (25 Xo) ~11000 crystals • Photomultiplier readout (no magnetic field) • Pre-amp based on QIE chip (KTeV) • Energy resolutionStochastic term 1.8% Constant term 0.33% • Position resolution

  29. PbWO4 Calorimeter Properties Property Value Density(gm/cm2) 8.28 Radiation Length(cm) 0.89 Interaction Length(cm) 22.4 Light Decay time(ns) 5(39%) (3components) 15(60%) 100(1%) Refractive index 2.30 Max of light emission 440nm Temperature Coefficient (%/oC) -2 Light output/Na(Tl)(%) 1.3 Light output(pe/MeV) into 2” PMT 10 Property Value Transverse block size 2.7cm X 2.7 cm Block Length 22 cm Radiation Length 25 Front end Electronics PMT Inner dimension +/-9.8cm (X,Y) Energy Resolution: Stochastic term 1.8% Constant term 0.33% Spatial Resolution: Outer Radius 140 cm--215 cm $ driven Total Blocks/arm 11,500

  30. Electromagnetic Calorimeter Tests Block from China’s Shanghai Institute 5X5 stack of blocks from Russia readyfor testing at Protvino • Lead Tungstate Crystals from Shanghai, Bogoroditsk, other vendors • Verify resolution, test radiation hardness (test beam at Protvino) • Test uniformity

  31. Preliminary Testbeam Results • Resolution (energy and position) close to expectations • Some non-uniformity in light output • more Radiation Hardness studies Energy Resolution Position Resolution

  32. EM calorimetry CLEO barrel e=89% * radius

  33. Muon System • Provides Muon ID and Trigger • Trigger for interesting physics states • Check/debug pixel trigger • fine-grained tracking + toroid • Stand-alone mom./mass trig. • Momentum “confirmation” • Basic building block: Proportional tube “Planks” ~3 m toroid(s) / iron 2.4 m half height track from IP

  34. Physics Reach (CKM) in 107 s J/y m+m-

  35. Concluding Remarks PAC Recommendation “ … BTeV has designed and prototyped an ambitious trigger that will use B decay displaced vertices as its primary criterion. This capability, together with BTeV’s excellent electromagnetic calorimetry and particle ID and enormous yields, will allow this experiment to study a broad array of B and Bs decays. BTeV has a broader physics reach than LHCb and should provide definitive measurements of CKM parameters and the most sensitive tests for new physics in the flavor sector.” C0 Hall at the Tevatron

  36. Additional Transparencies

  37. Changes wrt Proposal in Event Yields & Sensitivities • We lost one arm, factor = 0.5 • We gained on dileptons • From RICH ID • in proposal we used only m+m-, now we include e+e- • factor = 2.4 (or 3.9), depending on whether analysis used single (dilepton) id • We gained on bandwidth, factor = 1.15 • Gained on eD2 for Bs only,factor = 1.3

  38. Examples

  39. Reconstructed Events in New Physics Modes: Comparison of BTeV with B-factories

  40. Comparisons with LHCb • Advantages of LHCb • sb 5x larger at LHC, while st is only 1.6x larger • The mean number of interactions per beam crossing is 3x lower at LHC, when the FNAL bunch spacing is 132 ns • Advantages of BTeV (machine specific) • The 25 ns bunch spacing at LHC causes increased electronic noise. It makes 1st level detached vertex triggering more difficult; in fact LHCb only does vertexing in level 2

  41. Comparisons with LHCb II • The 7x larger LHC beam energy causes problems: much larger range of track momenta that need to be analyzed and large increase in track multiplicity, which causes triggering and tracking problems • The long interaction region at FNAL, s=30 cm compared with 5 cm at LHC, somewhat compensates for the larger number of interactions per crossing, since the interactions are well separated • There is an ion-trapping problem that stops them from moving their silicon closer than ~1 cm (compared to 6 mm for BTeV)

  42. Comparisons with LHCb III • Advantages of BTeV (detector specific) • BTeV has vertex detector in magnetic field which allows rejection of high multiple scattering (low p) tracks in the trigger • BTeV is designed around a pixel vertex detector which has much less occupancy, and allows for a detached vertex trigger in the first trigger level. • Important for accumulation of large samples of rare hadronic decays and charm physics. • Allows BTeV to run with multiple interactions per crossing, L in excess of 2x1032 cm-2 s-1 • BTeV will have a much better EM calorimeter • BTeV is planning to read out 5x as many b's/second

  43. Specific Comparisons with LHC-b Yields in important final states LHC-b BTeV

  44. Fundamentals: Decay Time Resolution • Excellent decay time resolution • Reduces background • Allows detached vertex trigger • The average decay distance and the uncertainty in the average decay distance are functions of B momentum: <L> = gbctB = 480 mm x pB/mB direct y y from b L/s L/s CDF/D0 region LHC-b region

  45. Trigger

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