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Jets

First Jet Results using the Upgraded D0 Detector Nirmalya Parua (for the D0 Collaboration) State University of New York Stony Brook DPF 2002 College of William and Mary Williamsburg, Virginia, May 24-28, 2002. Jets. Jet is a collection of towers within a given cone R.

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Jets

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  1. First Jet Results using the Upgraded D0 DetectorNirmalya Parua(for the D0 Collaboration)State University of New York Stony BrookDPF 2002College of William and Mary Williamsburg, Virginia, May 24-28, 2002

  2. Jets Jet is a collection of towers within a given cone R Where is the azimuthal coordinate  is the pseudorapidity  = -ln tan(/2)

  3. Calorimeter Overview L. Ar in gap 2.3 mm Ur absorber Cu pad readout on 0.5 mm G10 with resistive coat epoxy Y Drift time 430 ns Z X • Liquid argon sampling • Stable, uniform response, rad. hard, fine spatial seg. • LAr purity important ( impurity <0.5 ppm) • Uranium absorber (Cu or Steel for coarse hadronic) • Compensating e/  1, dense  compact • Uniform, hermetic with full coverage • |h|< 4.2 (  2o), l int > 7.2 (total) • Energy Resolution • e: sE / E= 15% /ÖE+ 0.3% p: sE / E= 45% /ÖE + 4% (as measured in Run I)

  4. Jet Algorithms • Cone Algorithm in Run I (1992-1995) • Draw a cone of fixed size around a seed. • Compute jet axis by ET weighted mean and jet ET by summing over ET s. • Draw new cone around the new jet axis and recalculate axis and new ET. • Iterate Until stable. • Sensitive to soft radiation. • Improvements in RunII (2000 - ) • Use 4 vector scheme instead of ET • Add midpoints of jets as additional starting seeds. • Infrared safe

  5. Jets in Run I Inclusive jet spectrum and Dijet mass spectrum measured in RunI well described by pQCD

  6. Fermilab Accelerator Upgrade Chicago  Booster CDF DØ Tevatron p source Main Injector (new) • Two new machines at FNAL for Run II: • Main Injector 150 GeV conventional proton accelerator • Supports luminosity upgrade for the collider • Recycler • 8 GeV permanent magnet (monoenergetic) storage ring • permits antiproton recycling from the collider • Tevatron Status and Schedule • 1.8 Tev  1.96 TeV • Goal: ò L dt = 2 fb-1 in Run 2a 15 fb-1+ in Run 2b

  7. Bunch Structure gap used to form trigger and sample baselines 3.56us Run I 6x6 superbunch gap 396ns 4.36us 2.64us Run II 36x36 Detector readout and trigger system upgrade must take into account smaller bunch crossing time

  8. Jets in Run II Cross section 2 times larger compared to Run I for jets with pT > 400 GeV Higher statistics will improve knowledge of proton structure at large x and searches for physics beyond the standard model (e.g. search for compositeness, W’, Z’ etc...) will be very exciting.

  9. Overview of D0 Upgrade • Upgrade Calorimeter Readout • 2 Tesla solenoid magnetic field for central tracking system to facilitate charge and momentum measurement. • Silicon and fiber tracker detector. • Add scintillator detector in muon system for faster trigger • Add Pre-shower detectors. • Pipelined 3 Level trigger

  10. Upgrade of Calorimeter Readout preamp driver SCA(48 deep) FET 2” Cable replaced for impedence matching Bank 0 Trig. sum Calibration SCA (48 deep) peak SCA (48 deep) x1 Filter/ Shaper Preamp/ Driver base x8 Calorimeter SCA (48 deep) SCA (48 deep) Bank 1 1 48 A D C A n. Bu f f Fully instrumented with <0.1% bad readout channels. 55k readout channels

  11. Finer Debugging                                 …. ….                                  ADC counts   L1 SCA up   … …     L1 SCA down L2 SCA x8 down L1 SCA     About 0.5% SCA chips replaced. About 0.5% of the SCA chips are replaced up    x1 L2 SCA  ADC Good BAD

  12. Calibration Using Pulser Pulser signal injected here • Non linearity <0.5% for E>200 MeV • For Lower energy values non linearity is significant but can be parametrized.

  13. Jet energy Scale +jet Event Et=27 GeV Et=24 GeV Correction of the jet energy measured at the detector level to the jet energy at the particle level Offset, EO: Energy that is not associated with the hard interaction. Namely Uranium noise, Pile-up effect, multiple interaction etc. Response, Rjet: Calorimeter energy response to jets, typically <1 Measured by attributing energy imbalance in +jet events. Showering fraction S : Fraction of the jet energy that showered inside the cone. Depends on cone size.

  14. Jet Studies for Run II • Data Sample • - D0 RunII data taken during February and March 2002 • - p collisions at s = 1.96 TeV • - Luminosity 1.9 pb –1 • Selection Criteria - || < 0.5 and cone jet of size 0.7 - Jet selection criteria based on EMF, CHF, HotF, n90 are imposed - Missing ET < 0.7 pTjet 1 - |Zvtx| < 50 cm - Ecal < 2 TeV -

  15. Jet triggers • Hardware Trigger: • Triggering on Calorimeter towers. • Fast trigger readout • multi tower trigger • current coverage || <0.8 Software Triggers Runs simple and fast jet algorithm on the precision readout.

  16. Results

  17. Multi jet events 3-jets event • ETjet1~310GeV • ETjet2~240GeV • ETjet3~110GeV • ET~8GeV 2-jets event • ETjet1~230GeV • ETjet2~190GeV

  18. Summary • D0 Detector is working well after upgrade. • Jet measurements are well underway. • First results available for • Inclusive jet pT spectrum (60 GeV < pT < 360 GeV) • Dijet mass spectrum ( 150 GeV < M <650 GeV) • Better understanding of the Detector and jet energy scale needed. • Looking forward to more data.

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