1. Recent Quarkonia Results from HERA-B
International Workshop on
Heavy Quarkonium 2006
June 27 – , Brookhaven National Laboratory
Martin zur Nedden
Humboldt-Universität zu Berlin
for the HERA-B Kollaboration

2. The HERA-B Experiment data taking up to march 2003
920 GeV protons
at the HERA storage ring
data taking up to march 2003
p + A  X , s = 41.6 GeV

3. Contents Introduction HERA-B Detector
Reference J/ψ-Production Cross Section
Charmonium Production:
J/ψ: Kinematical Distributions
J/ψ: Nuclear Dependence
Polarisation Measurement
ψ(2S) Production
χc Production
Beauty Production
Υ Production Cross Section
Inclusive Beauty Production Cross Section

4. Part 1 Introduction HERA-B Detector
Reference J/ψ-Production Cross Section
Charmonium Production:
J/ψ: Kinematical Distributions
J/ψ: Nuclear Dependence
Polarisation Measurement
ψ(2S) Production
χc Production
Beauty Production
Υ Production Cross Section
Inclusive Beauty Production Cross Section

5. Proton-Nucleus Interaction
PDF
hadronization
long distance (~1/(mcv)) process
non-perturbative calculations +
input from experiments
qq formation
short distance (~1/mc) / high momentum process
 perturbative calculations

6. Study of Charmonium Suppression
J/
state formation effects:
nuclear absorption
comover absorption
multiple scattering + energy loss
initial state effects:
shadowing (nuclear PDFs)
parton energy loss
intrinsic charm
HERA-B:
measurement of a for 2 wire materials:
a ≠ 1  “suppression”

7. xF-Dependence of Nuclear Suppression
J/ 
formation time and length:
 (xF) =   c 
 = (xF) boost of J/ w.r.t. nucleus
for c = 0.5 fm xF
 [fm]
0.2 30 10
-0.2 4

8. Part 2 Introduction HERA-B Detektor
Reference J/ψ-Production Cross Section
Charmonium Production:
J/ψ: Kinematical Distributions
J/ψ: Nuclear Dependence
Polarisation Measurement
ψ(2S) Production
χc Production
Beauty Production
Υ Production Cross Section
Inclusive Beauty Production Cross Section

9. The HERA-B Detector
p-beam
z [cm]
12C
48Ti
184W

10. The Dilepton Trigger
HERA-B detector: data is read out and buffered for 12 s (proton bunches cross every 96 ns, 0.5 interactions/BX)
PreTriggers: ECAL cluster or muon hit coincidence as trigger seed (custom hardware)
5 MHz
First Level Trigger (FLT): Track trigger in hardware using tracking detectors, seeding by pretriggers
3 MHz
Second Level Trigger (SLT): FLT tracking confirmed, extrapolation to vertex detector, 2 track vertex fit (PC farm)
20 kHz
Fourth Level Trigger (4LT): online reconstruction (and filtering) on PC farm, ca rec. J/ψ per h
100 Hz
100 Hz

11. Di-Lepton triggered Data Sample
J/ → 
~ 177, σ = 44 MeV/c2
J/ → e+e-
~ 108,000 J/
σ = 64 MeV/c2
J/
~ 3000 (2S)
/ 
(2S)
~ 1600 (2S)
absolute cross sections from di-lepton triggered data
need reference cross section

12. Part 3 Introduction HERA-B Detector
Reference J/ψ-Production Cross Section
Charmonium Production:
J/ψ: Kinematical Distributions
J/ψ: Nuclear Dependence
Polarisation Measurement
ψ(2S) Production
χc Production
Beauty Production
Υ Production Cross Section
Inclusive Beauty Production Cross Section

13. J/ Production Cross Section from Minimum Bias data
important for cross section normalisation of all di-lepton triggered data based measurements
+-
e+e-
independent data sample
efficiency and luminosity well understood
 systematic uncertainties small (usually dominant)

14. J/ψ (MinB): A-Dependence and ResultsTi W
α = 0.96  0.01
(fixed to E866)
results:

15. J/y (MinB) : Combination with other Experiments
reference cross section is extracted by QCD
inspired fit including all available data
(see talk of A. Spengler)
Hera-B
fit results at HERA-B energy
s = 41.6 GeV:

16. Part 4 a Introduction HERA-B Detector
Reference J/ψ-Production Cross Section
Charmonium Production:
J/ψ: Kinematical Distributions
J/ψ: Nuclear Dependence
Polarisation Measurement
ψ(2S) Production
χc Production
Beauty Production
Υ production Cross Section
Inclusive Beauty Production Cross Section

17. J/ pT Distributions (Nuclear Dependence)
standard fit:
preliminary data (di-electron only), compared with p-A results at similar energy (√s = 38.8 GeV)
[GeV-2]
E789 (Au)
HERA-B (C)
E771 (Si)
E672/E706 (Be)
(×10-4)
(×10-1)
(×10)
pT [GeV]
HERA-B (Ti)
HERA-B (W)
(×10-2)
(×10-3)
<pT> [GeV/c] A C Si Ti Au W Be
<pT> grows logarithmically with A:

18. J/ pT Distributions (Nuclear Dependence)
Cronin effect
<pT> grows with s:
<pT>  ·s

19. J/ψ xF - Distribution

20. J/ψ: Nuclear Dependence
muon data only
data sample of 2 – wire runs with
different materials (carbon/tungsten)
first measurement at xF < -0.1:
constant small suppression
R.Vogt, [Nucl.Phys.A700(2002)539.]
 = ± 0.003stat ± 0.021sys

21. tan  = pT/MJ/  only for pT  0 are the systems different
J/ Polarisation
usually only  is given
polarisation depends
on reference system:
E771, E672/E706
(Gottfried-Jackson)
(Collins-Soper)
E866
hadron CM
(hadron CM)
CDF
tan  = pT/MJ/  only for pT  0 are the systems different

22. Preliminary Polarisation Results
HCM GJ CS
large
polarisation
at pT=0
 max. in CS frame  „natural“ system ?

23. Part 4 b Introduction HERA-B Detector
Reference J/ψ-Production Cross Section
Charmonium Production:
J/ψ: Kinematical Distributions
J/ψ: Nuclear Dependence
Polarisation Measurement
ψ(2S) Production
χc Production
Beauty Production
Υ production Cross Section
Inclusive Beauty Production Cross Section

24. ’/ J/ Production Ratio
electron sample
muon sample

25. Kinematical Distributions
Carbon
Tungsten
J/→
J/→
, ee
A-dependence:(xF) =‘- 
CEM for color-1 nuclear absorption
NRQCD for color-1 & -8 nuclear absorption
fit with const: (E866)=-0.026±0.005
all consistent with no xF dependence.
average of E866 and NA50 is used:
(E866, NA50)=-0.030±0.004

26. Feynman–xF Dependence of ψ’ Production Ratio
all targets included,
correct for nuclear effects with
(E866, NA50)
NRQCD
CEM
data are consistent
with both models
(and with no xF dependence)

27. y’ production: pT distributions
Carbon
Tungsten
J/→
J/→
tendency for a wider pT distribution of ′
(increasing with A?)

28. Ψ’ Polarisation Measurement
result of
compatible with no polarisation difference

29. Production Ratio ψ’ / J/ψ√s
in addition:  and ee measurements yield: A
 improvement of B‘():
(better than current PDG value)

30. Part 4 c Introduction HERA-B Detector
Reference J/ψ-Production Cross Section
Charmonium Production:
J/ψ: Kinematical Distributions
J/ψ: Nuclear Dependence
Polarisation Measurement
ψ(2S) Production
χc Production
Beauty Production
Υ production Cross Section
Inclusive Beauty Production Cross Section

31. after background subtraction
c Production
selection:
preliminary
2002/2003 data
(di-muon sample)
measurement:
fraction of J/ψ’s from χc:
kinematical distributions
background: mixed events
after background subtraction
entries/(10 MeV/c2)
2000 data sample:
370 ± 74 χc’s (μ+μ- + e+e-):
R(c) = 0.32 ± 0.06 ± 0.04
[Phys. Lett. B 561, 61 (2003)]
m(μ+μ-γ)-m(μ+μ-) [GeV/c2]
new data: 40 bigger χc statistics

32. background: mixed events after background subtraction
χc1 - χc2 Separation
preliminary
(a fraction of the
di-muon sample)
ET(γ) > 0.4 GeV
further step: separate different states by varying the selection cuts
background: mixed events
entries/(1 MeV/c2)
measure the
χc2 / χc1
production ratio
after background subtraction
m(μ+μ-γ)-m(μ+μ-) [GeV/c2]

33. Production Cross Section Ratio R(c)
preliminary evaluation (2002/2003 data):
(21 ± 5)% of the produced J/ψ’s come from χc decays
based on 1300 χc’s
reconstructed in the di-muon channel
(less than 10% of the total statistics)
E771 (p-Si)
E369/ 610/ 673 (p-Be)
π-A
2000
ISR (p-p)
expected final precision
2002/3 prelim.
E705 (p-Li)
CDF (p-p)
HERA-B

34. Part 5 a Introduction HERA-B Detector
Reference J/ψ-Production Cross Section
Charmonium Production:
J/ψ: Kinematical Distributions
J/ψ: Nuclear Dependence
Polarisation Measurement
ψ(2S) Production
χc Production
Beauty Production
Υ production Cross Section
Inclusive Beauty Production Cross Section

35. Beauty Production at HERA-B
RD: =5314 m
detached vertex analysis
open
pA bb + X
J/ + X’
e+ e- , + -
hidden
invariant mass analysis
Cross sections normalised to prompt J/
using the ‘NRQCD supported’ evaluation:
(pN  J/ X) = (502  44) nb/nucleon
(with  = 0.96  0.01)
pA  Υ + X
e+ e- , +-

36. Hidden Beauty Production
muon channel: 30.8 ± 7.4
electron channel: 75 ± 14 DY DY
comb
comb
Fit: A· ((1S) + (2S) + (3S)) + B · Drell-Yan + combinatorial
(1S) : (2S) : (3S) fixed to E605 results
shape from MC
from like-sign pairs

37. Hidden Beauty Production: Results
normalized to J/ refernece cross section
fit “modified Craigie”:
 NLO CEM
data are compatible with =1

38. Part 5 b Introduction HERA-B Detector
Reference J/ψ-Production Cross Section
Charmonium Production:
J/ψ: Kinematical Distributions
J/ψ: Nuclear Dependence
Polarisation Measurement
ψ(2S) Production
χc Production
Beauty Production
Υ production Cross Section
Inclusive Beauty Production Cross Section

39. Detached Vertex Analysis
B meson has a long life time ( ~ 9 mm at HERA-B kinematics)
~ 0.5 mm dilepton vertex resolution
J/ from a B decay will be detached from primary interaction
downstream
pA  bb X
b  J/ψ Y  e+e-/+- Y
upstream ℓ+
J/ψ b Y ℓ- IW Δz p
analysis cuts:
- decay lenght (Δz)
- impact parameter
normalization on the inclusive prompt J/ cross section.
 systematic error minimization

40. Open Beauty Data Sample
analysis of 2002/03 data:
e+e- and +- triggered data
C, W, Ti targets (1 for bb)
J/ acceptance: < xF < 0.15
(90% of bb cross section)

41. B Flavour Confirmation
τ = 1.39 ± 0.19 ps
Long lived candidates around J/ψ mass
B lifetime compatible with expected 1.54 ps (PDG)

42. Principle of the Cross Section Measurement
measurement relative to prompt J/Ψ-cross section
minimize systematics uncertainties
independent of lumi determination
mostly independent of production model and J/Ψ cross section
atomic number cross section dependence
Δ= in detector acceptance
R= relative efficiency 1
sum over target materials
C,W,Ti
B selection efficiency from MC

43. Open Beauty Production: R
relative to prompt J/
to minimize uncertainties
from efficiencies, luminosity …
-0.35 < xF < 0.1
0 < pT < 6 GeV
2000 data
combined result of 2000 and 2002/3 data:
R =  0.005stat  0.004sys
(syst. error mainly from B(bJ/))
PHYSICAL REVIEW D 73, (2006)
2000 data: Eur. Phys.J. C26 (2003) 345

44. Production Cross Section
Relative to prompt J/
to minimize uncertainties
from efficiencies, luminosity …
normalizing to J/ from Maltoni et al.:
(pN  J/ X) = (502  44) nb/N

45. Summary
HERA-B collected J/ and 220 Mio min.bias events on different nuclei
Results on charmonium production (partly preliminary):
J/  cross section
J/ : xF and pT distributions in a new negative xF range
J/ A dependence demonstrate a flat behavior in this region
Fraction of c and (2S) yields relative to J/
Open and hidden beauty cross sections
Final results on J/, Υ, b-cross section, c and (2S) are/will be publisched during 2006