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Status de DØ

Daniel BLOCH, François CHARLES, Walter GEIST, Denis GELÉ, Sébastien GREDER, Anne-Catherine LE BIHAN, Abdenour LOUNIS, Isabelle RIPP-BAUDOT DB : la prise de données et les premiers résultats (présentés à Moriond par Aurelio Juste), les objectifs de physique

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Status de DØ

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  1. Daniel BLOCH, François CHARLES, Walter GEIST, Denis GELÉ, Sébastien GREDER, Anne-Catherine LE BIHAN, Abdenour LOUNIS, Isabelle RIPP-BAUDOT DB : la prise de données et les premiers résultats (présentés à Moriond par Aurelio Juste), les objectifs de physique IR : étiquetage des quarks beaux DB, 28 Mars 2002 café du jeudi  Status de DØ

  2. >70 Instituts >500 physiciens Groupes Français : CPPM Marseille, DAPNIA Saclay, IPN Lyon, ISN Grenoble, IReS Strasbourg, LAL Orsay, LPNHE Paris 6 : 70 chercheurs & étudiants(12 thèses en cours) Café du jeudi 28 Mars 2002

  3. CDF Run 1b Run 2a Run 2b D0 #bunches 6x6 36x36 140x103 s (TeV) 1.8 1.96 1.96 typ L (cm-2s-1) 1.6x1030 8.6x1031 5.2x1032  Ldt (pb-1/week) 3.2 17.3 105 bunch xing(ns) 3500 396 132 interactions/xing 2.5 2.3 4.8 The Tevatron Run 2 Tevatron upgrade: • Increased energy 1.8 TeV  1.96 TeV • Increased luminosity 0.1 fb-1 2 fb-1  15 fb-1 Detector upgrades: • Higher event rates and backgrounds (electronics, DAQ, trigger) • Considerable expansion of the physics capabilities Physics opportunities: • Top • Higgs • New Phenomena • Electroweak • Beauty • QCD (Run 2a) (Run 2b) (Run 1) Café du jeudi 28 Mars 2002

  4. The Upgraded DØ Detector Builds on the strengths of DØ: • Excellent calorimetry with faster readout • Upgraded muon system for better m-ID Augments its tracker and trigger capabilities: • Inner tracking (silicon tracker, fiber tracker) with 2T superconducting solenoid • Preshowers • Pipelined 3-level trigger Café du jeudi 28 Mars 2002

  5. The Upgraded DØ Detector Inside collision hall before putting the wall Café du jeudi 28 Mars 2002

  6. Detector Commissioning; Timing in; Improve electronics, DAQ and offline First Collisions Run II start DØ roll-in Run 2 in 2001... and 2002 plans • Considerable fraction (~25%) of collected luminosity devoted to detector commissioning. • Significant progress in identification of “physics objects”: e, m, jets, electromagnetic and jet energy scales, etc. In the next few months: • Finish detector commissioning • Complete triggers and improve DAQ • Debugging, calibration, alignment • Refine reconstruction algorithms • … • Also looking forward to more integrated luminosity!!! 2002 Projected Integrated Luminosity Integrated Luminosity (pb-1) date Café du jeudi 28 Mars 2002

  7. Primary Vertex with SMT Tracking Silicon Microstrip Tracker (SMT) ~ 2.4 m • - ~800,000 readout channels • - 6 barrels (4 layers) with interspersed (F-)disks • 4 external large area (H-)disks for forward tracking (2 < |h| < 3) • Single (axial) and double sided (axial+stereo) detectors • 3D track reconstruction capabilities SMT half cylinder 100% commissioned Barrels: 95.2% operational F-disks: 95.8% operational H-disks: 86.5% operational Café du jeudi 28 Mars 2002

  8. y track x DCA: Distance of Closest Approach pT>3 GeV DCA resolution ~ 60 mm (unaligned!) beam spot ~ 30-40 mm Central Fiber Tracker (CFT) - 20 cm < r < 51 cm - 8 layers of axial and stereo 830 mm  scintillating fibers - ~12m long clear wave-guide to Visible Light Photon Counter (VLPC) • 9K operating temperature • 85% QE, excellent S/N - ~77k readout channels - Fast pick-off for trigger (SMT+CFT) Global tracks Completed CFT Mechanical axial: 100% readout stereo: 52% readout Fully commissioned by mid-April CFT tracks Café du jeudi 28 Mars 2002

  9. Wen candidates f h ET(cluster)/pT(track) Calorimeter Preserve excellent Run 1 calorimetry: • LAr sampling: stable, uniform response, rad. hard., fine spatial segmentation • U absorber (Cu/Steel for coarse hadronic) • Uniform, hermetic, full coverage (|h| < 4.2) • Compensating (e/p~1) • Good energy resolution … and upgrade electronics: • Reduced bunch spacing • L1 trigger • Preserve noise performance 100% commissioned ~55K readout channels ~0.1% dead/noisy 3-jets event ETjet1~310GeV ETjet2~240GeV ETjet3~110GeV Missing ET~8GeV Café du jeudi 28 Mars 2002

  10. Forward Trigger Scint A-f Scint PDTs Shielding Forward Tracker (MDTs) Bottom B/C Scint Muon System • Coverage to |h|<2 • Emphasize m-ID at all trigger levels • Momentum determination not precise (use inner tracking) • Good time resolution (~2.5 ns) of trigger scintillators to remove out-of-time background (cosmics) Zm+m- candidate event mmm~ 103 GeV CFT tracks matched to muon system 100% commissioned Café du jeudi 28 Mars 2002

  11. Only statistical errors Only statistical errors QCD Physics • Integrated luminosity: ~1 pb-1 • Not fully corrected distributions: • Preliminary correction for jet energy scale (but no unsmearing of resolution effects) • No correction for trigger (small kinks) or selection efficiencies Café du jeudi 28 Mars 2002

  12. J/m+m- pTrel = 1.25 GeV/c From m triggers (Central+Forward) Muon System only Tracking Mean = 3.08 ± 0.04 GeV Sigma = 0.78 ± 0.08 GeV pTrel = 1.01 GeV/c bb di-muon candidate B-Physics KS0p+p- Café du jeudi 28 Mars 2002

  13. B-Physics (cont’d) • Normalized m+jet differential cross-section (data sample <0.2 pb-1). • Trigger and reconstruction efficiencies and jet energy scale corrections included. • Consistent in shape with DØ Run I results in same kinematic region. • Transverse momentum of the m with respect to the jet axis is a good discriminant between direct bm and backgrounds. • Evidence for the b-content in the m+jet sample. Café du jeudi 28 Mars 2002

  14. Zee selection Zee candidate mee = 93.2 GeV SMT+CFT Global tracks Wen (no jets) selection Events/2 GeV/c2 Events/2 GeV/c2 MT (GeV/c2) MT (GeV/c2) Electroweak Physics (W/Z, Top, Higgs) Require 1 track-EM cluster match W(en)+jets selection 335 events Signal:~200 118 events Signal:~75 Estimated background (mostly g, p0) Café du jeudi 28 Mars 2002

  15. Important signature for new physics searches (SUSY, extra dimensions, etc). Determine MET resolution from inclusive di-electron sample w/ at least one track match. EM m2 m1 D Run 2 Preliminary EM 1 2 ET = 19.2 GeV  = 0.40  = 0.63 no track match pT = 28.2 GeV  = -0.10  = 6.20 charge = -1 pT = 9.82 GeV  = -1.48  = 2.88 charge = 1 m   = 41.5 GeV Missing ET =31.8 GeV New Phenomena Physics Di-EM+Missing ET channel Search for Trileptons • Trilepton events are one of the cleanest signatures of SUSY (e.g. chargino+neutralino production through W*) emm candidate event Café du jeudi 28 Mars 2002

  16. vers la physique du quark top … • Le fermion le plus lourd : mt = 174±5 GeV • Très courte durée de vie: 4 x10⁻²⁵s (pas d’état lié tq) • Désintégration t→Wb ∼100%(|Vtb|~1 à vérifier !!) avec W→qq’ (2/3) ou ℓ (1/3) • Production en paire (interaction forte) g→t t: 1000 événements attendus en 3 ans • ou bien par interaction faible W→tb : 100 événements • Dans tous les cas, il faut identifier les quarks b (2 quarks b par événement) • Intérêt pour la recherche du Higgs → bb et vers la SUSY : production de staus Café du jeudi 28 Mars 2002

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