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The BTeV Experiment: Physics and Detector

This article discusses the BTeV experiment, its physics goals, and the requirements of the detector. It covers topics such as CP violation, beamline, vertex detector, pixel detector, decay efficiency, trigger efficiency, and rare B decays. The article is written in English.

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The BTeV Experiment: Physics and Detector

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  1. The BTeV Experiment: Physics and Detector FPCP 2003 K. Honscheid Ohio State University FPCP 2003K. Honscheid Ohio State

  2. B Physics Today • CKM Picture okay • CP Violation observed • No conflict with SM sin(2b) = 0.734 +/- 0.054 >1011 b hadrons (including Bs) FPCP 2003K. Honscheid Ohio State

  3. B Physics at Hadron Colliders • Energy 2 TeV 14 TeV • b cross section ~100 mb ~500 mb • c cross section ~1000 mb ~3500 mb • b fraction 2x10-3 6x10-3 • Inst. Luminosity 2x1032 >2x1032 • Bunch spacing 132 ns (396 ns) 25 ns • Int./crossing <2> (<6>) <1> • Luminous region 30 cm 5.3 cm Tevatron LHC Large cross sections Triggering is an issue All b-hadrons produced (B, Bs, Bc, b-baryons) FPCP 2003K. Honscheid Ohio State

  4. Detector Requirements • Trigger, trigger, trigger • Vertex, decay distance • Momentum • PID • Neutrals (g, p0) FPCP 2003K. Honscheid Ohio State From F. Teubert

  5. 100mb 230mb Forward vs. Central Geometry Multi-purpose experiments require large solid angle coverage. Central Geometry (CDF, D0, Atlas, CMS) Dedicated B experiments can take advantage of Forward geometry (BTeV, LHCb) bg b production angle b production angle FPCP 2003K. Honscheid Ohio State

  6. Beam Line The BTeV Detector FPCP 2003K. Honscheid Ohio State

  7. 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 Doublet FPCP 2003K. Honscheid Ohio State

  8. Vacuum System The Pixel Detector II FPCP 2003K. Honscheid Ohio State

  9. Simulated B Bbar, Pixel Vertex Detector FPCP 2003K. Honscheid Ohio State

  10. L1 vertex trigger algorithm • Generate Level-1 accept if “detached” tracks in the BTeV pixel detector satisfy: (GeV/c)2 cm FPCP 2003K. Honscheid Ohio State

  11. 30 station pixel detector FPGA segment trackers Switch: sort by crossing number track/vertex farm (~2500 processors) Merge Trigger decision to Global Level 1 Level 1 vertex trigger architecture FPCP 2003K. Honscheid Ohio State

  12. Decay efficiency(%) Decay efficiency(%) B p+p-63 Bo K+p- 63 Bs DsK 74 Bo J/y Ks 50 B- DoK-70 Bs J/yK* 68 B- Ksp-27 Bo K*g 40 74% Efficiencies and Tagging Trigger Efficiency-Minimum Bias Events • For a requirement of at least 2 tracks detached by more than 6s, we trigger on only 1% of the beam crossings and achieve the following trigger efficiencies for these states (<2> int. per crossing): Trigger EfficiencyBsDsK E F F I C I E N C Y E F F I C I E N C Y N=1 N=1 N=2 N=2 N=3 1% N=3 N=4 N=4 Impact Parameter in units of s Impact Parameter in units of s FPCP 2003K. Honscheid Ohio State

  13. The Physics Goals • There is New Physics out there: • Baryon Asymmetry of Universe & by Dark Matter • Hierarchy problem • Plethora of fundamental parameters • … • B Experiments at Hadron Colliders are well positioned to: • Perform precision measurements of CKM Elements withsmall model dependence. • Search for New Physics via CP phases • Search for New Physics via Rare Decays • Help interpret new results found elsewhere (LHC, neutrinos) • Complete a broad program in heavy flavor physics • Weak decay processes, B’s, polarization, Dalitz plots, QCD… • Semileptonic decays including Lb • b & c quark Production • Structure: B(s) spetroscopy, b-baryon states • Bc decays FPCP 2003K. Honscheid Ohio State

  14. Liquid Gas Importance of Particle Identification BTeV RICH Detector FPCP 2003K. Honscheid Ohio State

  15. Measuring aUsing Borp  p+p-po • A Dalitz Plot analysis gives both sin(2a) and cos(2a)(Snyder & Quinn) • Measured branching ratios are: • B(B-rop-) = ~10-5 • B(Bor-p+ + r+p-) = ~3x10-5 • B(Boropo) <0.5x10-5 • Snyder & Quinn showed that 1000-2000 tagged events are sufficient • Not easy to measure • p0 reconstruction • Not easy to analyze • 9 parameter likelihood fit Nearly empty (r polarization) Slow p0’s Dalitz Plot for Borp FPCP 2003K. Honscheid Ohio State

  16. Yields for Borp • Based 9.9x106 background events • Bor+p- 5400 events, S/B = 4.1 • Boropo 780 events, S/B = 0.3 Boropo Signal Background po g g mB (GeV) FPCP 2003K. Honscheid Ohio State mB (GeV)

  17. minimum c2 non-resonant non-rp bkgrd resonant non-rp bkgrd Our Estimate of Accuracy on a • Geant simulation of Borp, (for 1.4x107 s) Example: 1000 Borp signal + backgrounds With input a=77.3o FPCP 2003K. Honscheid Ohio State

  18. Rare b Decays • Search for New Physics in Loop diagrams • New fermion like objects in addition to t, c or u • New Gauge-like objects in addition to W, Z or g • Inclusive Rare Decays including • bsg • bdg • bsl+l- • Exclusive Rare Decays such as • Brg, K*g • BK*l+l-Dalitz plot & polarization g, l+l- BoK*g FPCP 2003K. Honscheid Ohio State

  19. 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 will have a high resolution PbWO4 calorimeter • Developed by CMS for use at the LHC • Large granularityBlock size 2.7 x 2.7 x 22 cm3 (25 Xo) ~23000 crystals • Photomultiplier readout (no magnetic field) • Pre-amp based on QIE chip (KTeV) • Energy resolutionStochastic term 1.6% Constant term 0.55% • Position resolution FPCP 2003K. Honscheid Ohio State

  20. 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 1.6% (2.3%) Constant term 0.55% Spatial Resolution: Outer Radius 140 cm--215 cm $ driven Total Blocks/arm 11,500 FPCP 2003K. Honscheid Ohio State

  21. Electromagnetic Calorimeter Tests Block from China’s Shanghai Institute • Resolution (energy and position) close to expectations • This system can achieve CLEO/BaBar/BELLE-like performance in a hadron Collider environment! FPCP 2003K. Honscheid Ohio State

  22. 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 FPCP 2003K. Honscheid Ohio State

  23. Ali et. al, hep-ph/9910221 Polarization in BoK*om+m- • BTeV data compared to Burdman et al calculation • Dilepton invariant mass distributions,forward-backward asymmetrydiscriminate among the SM and various supersymmetric theories.(Ali, Lunghi, Greub & Hiller, hep-ph/0112300) • One year for K*l+l-, enough to determine if New Physics is present FPCP 2003K. Honscheid Ohio State

  24. Summary • Heavy quark physics at hadron colliders provides a unique opportunity to • measure fundamental parameters of the Standard Model with no or only small model dependence • discover new physics in CP violating amplitudes or rare decays. • interpret new phenomena found elsewhere (e.g. LHC) • Some scenarios are clear others will be a surpriseThis program requires a general purpose detector like BTeV with • an efficient, unbiased trigger and a high performance DAQ • a superb charged particle tracking system • good particle identification • excellent photon detection FPCP 2003K. Honscheid Ohio State

  25. Additional Transparencies FPCP 2003K. Honscheid Ohio State

  26. Physics Reach (CKM) in 107 s FPCP 2003K. Honscheid Ohio State

  27. A simplified trigger comparison FPCP 2003K. Honscheid Ohio State From U. Egede

  28. Unitarity Triangles Bd0  p+ p- Bd0  rp BS0  DS p Bd0  DK*0 BS0  DSK Bd0  D* p, 3p BS0  J/y f Bd0  J/yKS0 dg = c FPCP 2003K. Honscheid Ohio State From N. Harnew

  29. 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) FPCP 2003K. Honscheid Ohio State

  30. Forward Tracker Prototype Straw tracker being constructed for FNAL beam test summer/fall 2002 Drawing Of forward Microstrip tracker Predicted performance - Momentum resolution is better than 1% over full momentum and angle range FPCP 2003K. Honscheid Ohio State

  31. HPD Schematic for BTeV RICH HPD Pinout HPD Tube HPD Pixel array Pulse Height from 163 pixel prototype HPD. Note pedestal, 1, 2, 3 pe peaks FPCP 2003K. Honscheid Ohio State

  32. 3/8” diameter Stainless steel tubes (0.01” walls) “picket fence” design 30  (diameter) gold-plated tungsten wire Manifolds are brass soldered to tubes (RF sheilding important!) Front-end electronics: use Penn ASDQ chips, modified CDF COT card Try “D0 fast gas” 88% Ar - 10% CF4 - CO2or 50% Ar – 50% Eth. Basic Building Block: Proportional Tube “Planks” Prop Tube Planks FPCP 2003K. Honscheid Ohio State

  33. Plank Cosmic Ray Tests Cosmic Ray Test Stand FPCP 2003K. Honscheid Ohio State

  34. 7.6 MHz 800 GB/s 4 KHz 200 MB/s BTeV Data Acquisition Architecture L1 rate reduction: ~1/100 L2/3 rate reduction: ~1/20 FPCP 2003K. Honscheid Ohio State

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