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

OutlineOutline

• 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

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Calorimeters Tracker

Muon System

Beamline Shielding

Electronics

protons

20 m

antiprotons

The Run II DØ DetectorThe Run II DØ Detector

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DØ Tracker DØ Tracker

125 cm

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Muon SystemMuon System

Fully commissioned

Bottom B/C Scintillators

A- ScintPDTs

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)

• 6080 8-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

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Muon System PerformanceMuon 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 ’simproves momentum resolution

CHEP02 – 31st International Conference on High Energy Physics, Amsterdam, 24 – 31 July, 2002

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DDØØ’s First J/’s First J/ Candidates Candidates

• ~5 pb-1

• J/ vertex– pT(track)>2 GeV/c,

matched to a muon– Positive decay

length

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Run I J/ψ production cross section

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σ(J/ψ) =N(J/ψ)

L εkine εaccept εtrigger εreco εtrack-match

L : Luminosity 4.8 pb-1

εtrigger: di-muon trigger.

εreco: muon system only

εtrack-match: muons matched to central track

εkine: only simulate muons which reach muon chamber

εaccept: inactive material, etc.

Run II J/ψ production cross section

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~30% systematic uncertainty

4.8 pb-1 of data

region not measured in Run I

Run II J/ production cross section

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Jpsi SignalJpsi 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 : 129KUpsilon:17K

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θ = angle(J/ψlab,μJ/ψ)

I(θ) = 3/2/(α+3) (1+ α cos2 θ)

α = (σT -2σL)/(σT +2σL)

Future measurements: J/ polarization

MC

This distribution is Monte template to use to find J/ polarization.

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ConclusionConclusion

• First measurement in the new kinematic range. – Rapidity Range: 0.0-1.8– 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