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.