Quarkonia%20production%20with%20the%20HERA-B%20experiment

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Quarkonia production with the HERA-Bexperiment
J. Spengler, MPI Heidelberg
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The Hera-B Detector

• Fixed target detector at e-p ring HERA, Desy
• High rate forward spectrometer (lt 40MHz)
• Wire targets (different materials) in proton
  halo
• Proton beam at 920 GeV/c (vs 41.6 GeV)
• High resolution vertexing
• Very good particle ID for (e, ?, ?, K, p)
• Hardware track trigger for lepton pairs
• Multiple trigger level
• On-line event reconstruction

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The Hera-B Detector
Angular coverage in bending plane 15 - 220 mrad
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Data Sample

• Data taking 30. Oct 2002 - 3. Mar 2003
• 150 106 dilepton triggered events with
  300,000 J/?
• achieved J/? rates 1200 - 1400 / hour
• in 2000 30 - 40 / hour
• 210 106 minimum bias events
• achieved logging rates 1000 Hz (1.7 TB/d)
• 90 106 hard photon Glueball trigger

see posters of W. Gradl (Q21) and M. Villa (Q20)
see talk of A. Gorisek posters of T. Knöpfle
(S10), C. van Eldik (S8) and T. Zivko (S9)
see poster of M. Bruschi (Q22)
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Topics
1) pt distribution xF distribution
A-dependence Decay angle distribution 2)
?(2s) production 3) ?c/J/? production ratio 4) bb
cross section 5) ? production
J/?
e e- ? ?-
?(2s)
?c
bb
?(1-3s)
Disclaimer All results are preliminary
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J/? production e e-
80 of statistics 101,000 J/?width 64 MeV/c2
J/?
?(2S)
?
???
Dilepton mass accessible from 0 - 11 GeV/c2
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J/? production ??-
J/?
Approx. 3,000 eventsMass 3674 MeV/c2Width
53 MeV/c2
Approx. 177,000 eventsMass 3095 MeV/c2Width
44 MeV/c2
?(2S)
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pT distribution of J/?
80 of ee- sample
Parameterization
Target Exp. Range e? ?? error
C 920 lt 4.8 1.22 1.22 0.01
W 920 lt 4.8 1.29 1.30 0.01
Au 800 E789 lt 2.6 1.29 0.009
Si 800 E771 lt 3.5 1.20 0.01
stat. only
Results for ltpTgt
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xF distribution of J/?
Parameterization
10 of ee- sample
Is it adequate to describe the exp. data ??
Negative xF range accessible for the time
Target Exp. Range c
C, W 920 -0.35 ltxFlt0.15 (5-6.5)?0.3
Si 800 E771 -0.05 ltxFlt0.25 6.54?0.23
Au 800 E789 -0.035ltxFlt0.135 5.21?0.04
Au 800 E789 0.30ltxFlt0.95 4.91?0.18
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A-dependence of J/?
Parameterization of cross section
Determine ? from two different targets

• C (A12.0) and W (A183.8) target
• 25 of full ee- sample
• Ratio of efficiencies includes full detector
  trigger simulation
• Ratio of luminosities under investigation ?
  norm. to E866 result

stat. errors only
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A-dependence of J/?
NRQCD pred. R. Vogt Nucl. Phys. A700 (2002) 539
Expected stat. error for full data sample
BCKT pred. K.G. Boreskov, A.B. Kaidalov JETP.
Lett. 77 (2003) 599
HERA-B range
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cos? distribution of J/?
Parameterization
80 of ee- sample
J/? polarization described by parameter ? ?
(0,1,-1) ? (no, trans., long.) polarization
Target Exp. ?
C, W 920 (-0.50.1)?0.1
Be 530 E672/706 0.01?0.15
Be 800 E672/706 -0.11?0.15
Si 800 E771 -0.09?0.12
Cu 800 E866 0.069?0.08
Expected error of ? vs. pT (Muon channel)
Important tests of models
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?(2S) to J/? ratio

• Measure ?(2S)?ee- relative
• to J/ ? to reduce systematic
• uncertainties
• Carbon target
• 30 of ee- statistics used
• nJ/? 30k
• n?(2S) 650

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?(2S) to J/? ratio

• ?J/? / ? ?(2S) 0.72?0.01
• Stat. errors only
• Use ?(J/?) 357827 nb/N based on E771 and
  E789 results

R?(2S) 0.13 0.02 ??(2S) 46 12 nb/N
Systematic studies ongoing Muon channel gives
compatible result
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?c to J/? production ratio

• ECAL resolution does not allow to separate ?c1
  and ?c2 states (?m 46MeV). ?c0 neglected due to
  small Br.
• ?? 0.4

Results of 2000 (Phys.Lett. B561(2003) 61 N(?c)
370?74 (both ??-, ee-) R(?c)
0.32?0.06?0.04
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?c to J/? production ratio

• Analysis of 2002/03 data
• Comb. background by event mixing
• Carbon target
• In 15 of ??- statistics we find about 1300 ?c
• Expect N(?c) 15k for full sample

R(?c) 0.210.05
Systematic studies ongoing Electron channel gives
compatible result
?m (GeV/c2)
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pA ?bb X, b?J/?Y
Method Detached vertex analysis to separate B
signal (decay length 7 mm) from direct J/?
Results of 2000 Eur. Phys.J. C26(2003)
345 ee- ??-

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pA ?bb X, b?J/?Y

• Analysis of 2002/03 data
• 35 of ee- and ??- statistics
• Expect NB 100 for full sample
• Carbon Tungsten target
• J/? acceptance -0.35ltxFlt0.15 (90 of bb cross
  section)

• Preliminary results of both channels compatible
• 1.5 ? lower than 2000 measurement

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pN ?? X, ????-, ee-
Drell-Yan contribution compatible with E866
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pN ?? X, ????-, ee-
Events Br d?/dy?y0
??- 337 3.91.1 pb/N
ee- 3110 2.91.2 pb/N
both 3.40.8 pb/N

• All C and W data used
• Relative production of ?(1S)/?(2S)/?(3S) fixed
  on E605 data
• ? shapes taken from MC
• Modified Craigie applied to allow for nuclear
  suppression ?0.99?0.05

vs (GeV)
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Summary

• HERA-B has finished data taking.
• Large dilepton sample (both ??-, ee-) allows
  for detailed study of J/? (300k), ?(2S), ? and
  bb-production
• Quality of data is very good
• HERA-B has large acceptance (negative xF) and
  good particle identification
• Analysis of 2002/03 data in progress
• First preliminary results presented
• New collaborators welcome to contribute to
  analysis of this rich data sample