APS Meeting April 5-8, 2003 at Philadelphia Chunhui Luo 1 Chunhui Luo Inclusive J/ψ Production at DØ

APS Meeting April 5-8, 2003 at Philadelphia Chunhui Luo 2 Outline D0 detector elements crucial for the J/ψ cross section measurement Summary of Run I Results J/ ψ signal in Run II Cross Section Determination Future Polarization Measurement Aims –Test of Quantum Chromodynamics (QCD) –Test of the Detector performance

APS Meeting April 5-8, 2003 at Philadelphia Chunhui Luo 3 Calorimeters Tracker Muon System Beamline Shielding Electronics protons 20 m antiprotons The Run II DØ Detector

APS Meeting April 5-8, 2003 at Philadelphia Chunhui Luo 4 DØ Tracker 125 cm

APS Meeting April 5-8, 2003 at Philadelphia Chunhui Luo 5 Muon System Fully commissioned Bottom B/C Scintillators A-  Scint PDTs Forward Tracker (MDTs) Shielding Forward Trigger Scintillators Central and Forward regions, coverage up to  = ± 2 Three layers: one inside (A), two outside (B, C) the toroid magnets Consists of scintillators and drift tubes Central Proportional Drift Tubes (PDT’s) 6624 drift cells (10.1  5.5 cm) in 94 three- and four-deck chambers Central Scintillation Counters 360 “cosmic ray” counters outside the toroid (  = 22.5  ) 630 “A  ” counters inside (  = 4.5  ),  = 0.1 Forward Mini Drift Tubes (MDT’s) cell tubes in 8 octants per layer on North and South side, cell cross-section 9.4  9.4 mm Forward Scintillation Counters (Pixels) 4214 counters on the North and South side  = 4.5  matches the MDT sector size

APS Meeting April 5-8, 2003 at Philadelphia Chunhui Luo 6 Muon System Performance M = 3.08  0.04 GeV  = 0.78  0.08 GeV Muon stand alone system Muon plus central tracking J/  invariant mass Matching of central tracks to  ’s improves momentum resolution CHEP02 – 31 st International Conference on High Energy Physics, Amsterdam, 24 – 31 July, 2002

APS Meeting April 5-8, 2003 at Philadelphia Chunhui Luo 7 DØ’s First J/  Candidates ~5 pb -1 J/  vertex –p T (track)>2 GeV/c, matched to a muon –Positive decay length

APS Meeting April 5-8, 2003 at Philadelphia Chunhui Luo 8 Run I J/ψ production cross section

APS Meeting April 5-8, 2003 at Philadelphia Chunhui Luo 9 σ(J/ψ) = N(J/ψ) L ε kine ε accept ε trigger ε reco ε track-match L : Luminosity 4.8 pb -1 ε trigger : di-muon trigger. ε reco : muon system only ε track-match : muons matched to central track ε kine : only simulate muons which reach muon chamber ε accept : inactive material, etc. Run II J/ψ production cross section

APS Meeting April 5-8, 2003 at Philadelphia Chunhui Luo 10 ~30% systematic uncertainty 4.8 pb -1 of data region not measured in Run I Run II J/  production cross section

APS Meeting April 5-8, 2003 at Philadelphia Chunhui Luo 11 Jpsi Signal By January 2003, 129K J/ψ ‘s are collected Integrated Luminosity: 50 Pb -1 σ(J/ψ) = 78 ± 3 MeV N(J/ψ) = 129,024 Invariant Mass (GeV) J/ψ : 129K Upsilon:17K

APS Meeting April 5-8, 2003 at Philadelphia Chunhui Luo 12 θ = angle(J/ψ lab,μ J/ψ ) I(θ) = 3/2/(α+3) (1+ α cos 2 θ) α = (σ T -2σ L )/(σ T +2σ L ) Future measurements: J/  polarization MC This distribution is Monte template to use to find J/  polarization.

APS Meeting April 5-8, 2003 at Philadelphia Chunhui Luo 13 Conclusion First measurement in the new kinematic range. –Rapidity Range: –Energy of Central Mass: 1.98 TeV –Consistent with Run I measurement Near Future –Cross Section measurement using full statistics and improved reconstruction software for Jpsi and upsilon states –Reconstruct  c -> J/   decay –J/ , upsilon Polarization measurement will be measured