1. Charm Production at HERA and at Hadron-Colliders
Quarkonia in Media / Production
Charm Production at HERA and at Hadron-Colliders
International Conference
Charm 2009
May 20 – , Heidelberg, Germany
Martin zur Nedden
Humboldt-Universität zu Berlin

2. Content Charm Production Experiments Physics Results Introduction
Hadronic Interaction
Electron-Proton Interaction
Experiments
HERA, TEVATRON and LHC
Detectors and Spectrometers
Physics Results
D*-Production and F2c
Charm Fragmentation
Charmonium Production
W + charm-Jet production
Rare Decays and Flavor Changing Neutral Currents

3. Content Charm Production Experiments Physics Results Introduction
Hadronic Interaction
Electron-Proton Interaction
Experiments
HERA, TEVATRON and LHC
Detectors and Spectrometers
Physics Results
D*-Production and F2c
Charm Fragmentation
Charmonium Production
W + charm-Jet Production
Rare Decays and Flavor Changing Neutral Currents

4. Charm Production At HERA: At LHC open Charm charmonium spectroscopy
contribution to F2
charm fragmentation
charmonium spectroscopy
excited charmed states
production in media (HERA-B)
At LHC
charmonium spectroscopy
charmonium polarization
detector calibration
trigger commissioning
Not all can be covered here…
At TEVATRON:
D0 mixing and CP violation (talk of Angelo di Canto)
excited charmed states (talk of Kai Yi)
FCNC
charm fragmentation, W + c-Jets
charmonium spectroscopy and polarization

5. Hadronic Production of Heavy Quarks
Parton-Density-Function
within the hadron
partonic
cross setion
hadronisation:
formation of
hadrons with
heavy quarks
or quarkonia
stats
factorisation of the process
production in hadronic interaction

6. Heavy-Quark production in Hadron Collisionsg Q
Flavor excitation g
Flavor creation g g
radiative corrections
Gluon splitting
Leading Order and Next to Leading Order
B/D-Hadrons and/or b/c-jets are the observables for b/c-quark
Proton structure: HERA
Fragmentation: HERA/TEVATRON
NLO QCD

7. Quarkonia Formation qq formation: production of heavy quarks in media
PDF
Hadronization/Fragmentation:
formation of final state wiht charm
long distance (~1/(mcv)) process:
non-perturbative calculations and
input from experiments needed,
model dependence:
CSM, COM, CEM, NRQCD
qq formation: production of heavy quarks in media
short distance (~1/mc) / high momentum process:
perturbative calculation

8. Quarkonia Production Models
From NRQCD, Color Octet
Mechanism
- colour radiated off by soft gluons
adjustable hadronization parameter:
→ match measured pT spectras and
cross section
predicts transverse polarization,
increasing with pT
Color Singlet Model
- can’t produce colour-neutral JP = 1- cc pair
by simple gluon fusion.
- produce a coloured state and one hard
gluon carries away color
- pT spectrum does not match data
- Underestimates cross sections by factors of

9. Heavy Quark Production in Electron-Proton Scattering
direct process:
boson gluon fusion
main contribution
Charmonium
formation at HERA
J/Y ( pJ/y)
indirect process:
resolved photon
indirect process:
flavor excitation
Two kinematic regimes:
• Photoproduction (PHP)
with Q2 ~ 0
• Electroproduction (DIS)
with Q2 > 2 GeV2

10. Content Charm Production Experiments Physics Results Introduction
Hadronic Interaction
Electron-Proton Interaction
Experiments
HERA, TEVATRON and LHC
Detectors and Spectrometers
Physics Results
D*-Production and F2c
Charm Fragmentation
Charmonium Production
W + charm-Jet Production
Rare Decays and Flavor Changing Neutral Currents

11. The HERA Experiments e+p: s = 320 GeV ZEUS H1 HERA I: 1994 – 2000
HERA II: H1
Total lumi on tape:
~ 0.5 fb-1 per experiment

12. The HERA-B Spectrometer
Spectrometer at the HERA storage ring: proton-fixed target
920 GeV protons
p+A  X , s = 41.6 GeV
150 M di-lepton trigger events
~ J/ψ
~ c
~ ψ’
210 M minimum bias events

13. Tevatron Experiments p+ p: √s = 1.96 TeV CDF Total lumi on tape:
~ 3 fb-1 per experiment D0

14. The ATLAS Experiment at LHC
p + p: √s = 14 TeV

15. A transverse slice through CMS (LHC)

16. The LHCb Spectrometer Muon System RICH Detectors Vertex Locator
p + p: √s = 14 TeV
Muon System
RICH Detectors
Vertex Locator
pp collision Point
~ 1 cm B
Calorimeters
Tracking System

17. Content Charm Production Experiment Physics Results Introduction
Hadronic Interaction
Electron-Proton Interaction
Experiment
HERA, TEVATRON and LHC
Detectors and Spectrometers
Physics Results
D*-Production and F2c
Charm Fragmentation
Charmonium Production
W + charm-Jet Production
Rare Decays and Flavor Changing Neutral Currents

18. Selection of charmed Mesons
Production of charm-quarks in
ep-interaction via boson-gluon-fusion
Identification of D*+ via the
mass difference ΔM of the
invariant masses
Momentum transfer Q2 = -q2 = (k’-k)2
Momentum fraction x of scattered quark
Looking for charm within the decay
chanel of D*-mesons

19. Open Charm-Production at HERA
HERA I : PDF –central measurement of HERA
PDF obtained from the fits to inclusive F2
Inclusive F2 experimentally very precise
Contribution of events with charm to F2 high
Measurement of F2c has large uncertainties
HERA II: precise PDF – crucial importance for the LHC
Combined HERA PDF are of unprecedented precision
BUT dependent on parameterization of the QCD fit
Need a cross check / direct access to the gluon
Final state measurements (jets, heavy quarks) extremely important
F2c at HERA II on the way to precision measurement

20. D* Production, Q2 dependence
Measurement for DIS (5 GeV2 < Q2 < 100 Q2) and
high Q2 data (up to Q2 = 103 GeV2)
Full HERA statistics:
~350 pb-1
Good description by NLO calculations

21. D* in DIS (low Q2)
Differential cross sections measured in Q2, x, pT and η
Reasonable described by NLC QCD calculation
Double differential cross section in x and Q2 enables the extraction of F2c
Double differential,
η in bins of pT

22. HERA Measurement of F2c Problem: detector acceptance of ~30%
→ strong model dependence due
to large extrapolation factors
Comparison of different analysis methods
- inclusive lifetime (H1, HERA I + II)
- μ pTrel (ZEUS, HERA II)
- D+, D0, Ds cross sections (ZEUS, HERA II)
- D+ and lifetime (ZEUS, HERA II)
Theory prediction differ for Q2 < (2mc)2

23. HERA Measurement of F2c Different methods agree well
combination of measurements
will improve precission
Strong rise towards low x at lager Q2
Different inputs to the theoretical
predictions:
- parton densities
- mass treatment
- charm fragmentation

24. Content Charm Production Experiment Physics Results Introduction
Hadronic Interaction
Electron-Proton Interaction
Experiment
HERA, TEVATRON and LHC
Detectors and Spectrometers
Physics Results
D*-Production and F2c
Charm Fragmentation
Charmonium Production
W + charm-Jet Production
Rare Decays and Flavor Changing Neutral Currents

25. Charm Fragmentation D* Peterson: Kartvelishvili:
parton scattering cross section
(perturbative)
parton density function
(non perturbative)
fragmentation function
(non perturbative) D*
Peterson:
Kartvelishvili:

26. Fragmentation Function
ET(Jet) > 9 GeV, inclusive kT algorithm
Data described by NLC QCD calculations with
Peterson or Kartvelishvili fragmentation

27. Fragmentation Function
for shape comparison to
Other experiments
normalization to 1/binwith
for z>0.3
With PYTHIA phase space
extrapolated to pT(D*) =0
and finite bin size to
extract the mean value of z:

28. Content Charm Production Experiment Physics Results Introduction
Hadronic Interaction
Electron-Proton Interaction
Experiment
HERA, TEVATRON and LHC
Detectors and Spectrometers
Physics Results
D*-Production and F2c
Charm Fragmentation
Charmonium Production at HERA-B and LHCb
W + charm-Jet Production
Rare Decays and Flavor Changing Neutral Currents

29. Nuclear Effects for Charmonium Production
J/
final state formation effects:
nuclear absorption
comover absorption
multiple scattering + energy loss
initial state effects:
shadowing (nuclear PDFs)
parton energy loss
intrinsic charm
HERA-B: acsess to production in media measurement of a using C and W targets:
based on Glauber-model:
a ≠ 1  „dependence”

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

31. J/ pT Distributions of HERA-B
HERA-B combined result
HERA-B
E672/706/771/789
NA50
Increase of <pT2> with
A (radius of nucleus):
linear dependence on the
nuclear path length of
the incident parton

32. *J/ψ xF – Distribution of HERA-B
HERA-B combined result
wxF : width
ΔxF : shift
width increasing with
Radius of nucleus
shift increasing with
Radius of nucleus
pT distribution:
increase of <pT2> with radius
xF distribution:
increasing width and shift with radius
both effects compatible with initial state energy loss

33. Nuclear Dependence Measurement: pT
pT broadening effect
as seen by E866
confirmed
Good agreement of E866 an
HERA-B measurement in the
common region of pT

34. Nuclear Dependence Measurement: xF
average α measurement form HERA-B:

35. J/ Production at LHCb Prompt J/ production not fully understood
- NRQCD (Colour Octet Model) successful in reproducing pT spectrum at Tevatron
- but predicts increasing transverse polarization at high pT (not observed)
Cross-section + polarization important probes of Charmonium production
- LHCb has unique acceptance
coverage in pT and 
- Synergy with b production
measurement

36. Identifying Prompt J/
J/ signal in 19 million min bias events
(1.1 s of running with nominal luminosity)
Mass resolution ~ 11 MeV
S/B ~ 4
Expect 3.2  106 events in 5 pb-1 at 8 TeV
separate J/ from prompt and b decays m+
Primary vertex m- dz
Prompt component:
Gaussian
J/ from B-meson decay: exponential
Combinatorical background

37. Polarization Effects Prompt J/ polarized
lab
direction
Helicity frame
Reconstucted events in
MC with no polarization
LHCb acceptance generates an
artificial polarization
Systematic of up to 25 %
cross-section measurement needs to account for polarization

38. χc Production of HERA-B
Selection by γ Selection (Eγ) and
invariant mass measurement
Relative measurement of χc to
J/ψ production
disentangle χc1 and χc2 by double Gaussian fits:
separate cross section measurements
background subtraction by mixed events

39. Event Counting HERA-B LHCb
Separation of χc1 and χc2 in the ΔM spectra:
double Gaussian fit with some fixed parameters predicted by MC
free parameters are the ratio and sum of event numbers
HERA-B
LHCb
Signal in inclusive
J/ events
ΔM ~ 27 MeV (cf M(c2 ) - M(c1 ) = 55 MeV )
Some sensitivity to ratio (c2 ) / (c1 )

40. Production Cross Section Ratio R(c)
HERA-B: Final result: Rχc = (18.8 ± 2.8)%
of the produced J/ψ’s come from χc decays
E771 (p-Si)
E369/ 610/ 673 (p-Be)
π-A
HERA-B 2000
ISR (p-p)
E705 (p-Li)
2002/3 final
CDF (p-p)
HERA-B

41. Content Charm Production Experiment Physics Results Introduction
Hadronic Interaction
Electron-Proton Interaction
Experiment
HERA, TEVATRON and LHC
Detectors and Spectrometers
Physics Results
D*-Production and F2c
Charm Fragmentation
Charmonium Production at TEVATRON (Y(2S))
W + charm-Jet Production
Rare Decays and Flavor Changing Neutral Currents

42. Ψ(2S) Signal Selection CDF preliminary 1.1fb-1 CDF preliminary 1.1fb-1
Selection: use clean di-muon sample
Separaion from prompt (2S) from long lived ones:
ct (prompt): double Gaussian,
ct (long lived): exp. conv. Gaussian
Fit in bins of pT for cross sections

43. Differential ψ(2S) cross-section
CDF preliminary 1.1fb-1
Inclusive total cross-section:
Prompt component of
total cross section
2 < pT((2S)) > 30 GeV
| y((2S)) | < 0.6

44. Ratio of Cross Sections
Ratio of (2S) to J/
Ratio of ratios
CDF preliminary 1.1fb-1
CDF preliminary 1.1fb-1
long
lived
prompt

45. Polarization Acceptance depends on ψ(2S) polarization parameter α
Acceptance (A) and its systematics are determined assuming:
prompt :  = 0.01 ± 0.13
A = 2% at pT= 3 GeV
A = 20% at pT= 23 GeV
from B decays
eff = 0.35 ± 0.25 ± 0.03
A = 1.5% at pT= 3 GeV
A = 19% at pT= 23 GeV
Inclusive measurement uses
weighted average acceptance

46. Content Charm Production Experiment Physics Results Introduction
Hadronic Interaction
Electron-Proton Interaction
Experiment
HERA, TEVATRON and LHC
Detectors and Spectrometers
Physics Results
D*-Production and F2c
Charm Fragmentation
Charmonium Production at ATLAS/CMS
W + charm-Jets
Rare Decays and Flavor Changing Neutral Currents

47. Motivation for Charmonium at LHC
Large number of J/ψ→μ+μ- and Υ→μ+μ- decays is expected at LHC:
→ alignment and calibration of trigger and tracking
→ test for QCD calculations
→ prompt quarkonia is a main source of background to (rare) B processes
Key player in the early data taking:
→ At low luminosity lower pT threshold possible to collect large physics sample
→ ATLAS reach larger pT as TEVATRON: enhance its analysis power
Pb-Pb collisions at high energies and luminosities:
→ The Pb-Pb runs will occur at 5.5 TeV per NN collision,
with 1027 cm-2s-1 Pb-Pb instantaneous luminosity
→ Quarkonium states will be produced with very high rates 47

48. Expected Quarkonia data at early LHC
85 pb-1
60 pb-1
ATLAS
D fb-1
CDF 1.1 fb-1
Tevatron
1x J/ψ
4.2x 
~1000 J/ψ’s per hour expected
60 pb-1 should allow for competitive measurement of quarkonium polarization,
with enough statistics in the crucial high pT region.
High pT data is important since TEVATRON suffers from statistics in this region.
With 10 pb-1 ATLAS will be able to measure ratios of quarkonia cross sections,
which can help to constrain NRQCD octet matrix elements. 48

49. Inclusive Differential J/ψ cross sections
The observed J/ yield results from:
direct production
decays from ’ and c states
decays from B hadrons
CMS will measure the inclusive, prompt and non-prompt (B decays) production cross sections
In 1 or 2 days at 1031 cm-2s-1 (1 pb-1 of integrated luminosity), CMS will collect ~ J/ events
The J/ yield is extracted by fitting the dimuon mass distribution, separating the signal peak from the underlying background continuum
CMS simulation

50. Quarkonium production cross-section
MC Onia production pT and the differential cross-section contributions from color singlet, color octet and singlet/octet of  .
Tevatron (1.8 TeV)
The dominant contribution at high
pT range is the 3S1 color octet
fragmentation (dashed dotted line).
LHC MC (14 TeV)
 production cross section
J/Ψ prod. cross section 50

51. Polarization definition
Polarizations studies were using the angular distribution of the daughter particles, μ+, produced in the particle decay.
The angle θ* is measured with respect to the direction of the movement in the ATLAS lab frame.
The polarization parameter α, defined as
Transverse polarization α = +1 refers to helicity ±1.
Longitudinal (helicity 0) polarization α = -1 .
Un-polarized production consists of equal fractions
of helicity states +1, 0 and -1,
and corresponds to α= 0.
J/Ψ rest frame
J/Ψ lab
direction 51

52. Differential J/ψ cross section
CMS simulation
CMS simulation
pp at 14 TeV 3 pb-1  ~ J/
A : convolution between the detector acceptance and the trigger and reconstruction efficiencies, which depend on the assumed polarization
corr : needed if MC does not match “reality”
Competitive with Tevatron results after only 3 pb-1

53. Quarkonium production in Pb-Pb collisions
dNch/dh = 3500
  -

54. J/y → m+m-: Acceptances and Mass Resolutions
material between the silicon tracker and the muon chambers (ECAL, HCAL, magnet iron)
prevents hadrons from giving a muon tag but impose a minimum muon momentum of
3.5–4.0 GeV/c. This is no problem for the Upsilons but sets a relatively
high threshold on the pT of the detected J/ψ’s.
low pT J/ψ acceptance: better at forward rapidities.
dimuon mass resolution is 35 MeV
pT (GeV/c) h
J/y
barrel + endcaps
barrel + endcaps
Acceptance
barrel
CMS simulation
pT (GeV/c)

55. pT reach of quarkonia measurements
0.5 nb-1 : 1 month at 4x1026 cm2s-1
expected quarkonia yields:
J/ψ : ~ ,  : ~
● produced in 0.5 nb-1
■ rec. if dN/dη ~ 2500
○ rec. if dN/dη ~ 5000
J/y
Statistical accuracy (with trigger) of ’/ ratio vs. pT should be good enough to rule out some models
CMS simulation 
CMS simulation

56. Content Charm Production Experiment Physics Results Introduction
Hadronic Interaction
Electron-Proton Interaction
Experiment
HERA, TEVATRON and LHC
Detectors and Spectrometers
Physics Results
D*-Production and F2c
Charm Fragmentation
Charmonium Production
W + charm-Jets
Rare Decays and Flavor Changing Neutral Currents

57. W + charm “μ-tagged jet” method: Consider the electric charge
Possible background to top, stop-quark and SM Higgs production
|Vcd|2 suppresses d-quark-gluon fusion production
⇒ Wc production provides direct sensitivity to s-quark PDFs
s-quark PDF is important for these processes at Tevatron/LHC:
A probe of s-quark PDF at hadron colliders tests QCD evolution
“μ-tagged jet” method:
Consider the electric charge
correlation of μ from c-quark and
lepton from W
Require events with opposite charge
NOS ≫ NSS

58. W+c-Jet Fraction W+c-jet selection with theory prediction
• All lepton channels considered
for W boson decay
• Z →μμ rejected by requiring
Mμμ<70 GeV for μ-channel
• σ(W+c-jet) fraction compared
with theory prediction in jet pT:
ALPGEN calculates the
matrix element
PYTHIA does showering
and hadronization
• Measurement is consistent
with theory prediction

59. W+c-Jet Cross Section
CDF measures total cross section of W+c-jet with ~1.8 fb-1 data
electron and muon channels considered for W boson decay
c-jet with pT(c) > 20 GeV/c and |η(c)|< 1.5:
c-jet identified from semileptonic decay by looking for a muon within jet
Measurement agrees with NLO calculation

60. Content Charm Production Experiment Physics Results Introduction
Hadronic Interaction
Electron-Proton Interaction
Experiment
HERA, TEVATRON and LHC
Detectors and Spectrometers
Physics Results
D*-Production and F2c
Charm Fragmentation
Charmonium Production
W + charm-Jets
Rare Decays and Flavor Changing Neutral Currents

61. Upper limit for D0→μ+μ–
Search for a signal of the FCNC decay D0→μ+μ– in all di-muon samples
Observed events: 3
Expected background: 6
Limit (90% CL):
best limit at publication time
[Phys. Lett. B596 (2004)173]

62. Experimental strategy CDF:
Search for FCNC D0→mm
SM expectation BR~ 3∙10-13
Best limit: <4.1∙ % CL, Beatrice/WA92,E771
Enhanced in N.P. (R-Parity Violation Susy: ~3.5*10-6)
Experimental strategy CDF:
Events from two-track trigger using first 69 pb-1 of data
To cancel acceptance effects normalize to D0→pp
Result:
BR(D0→mm) < 2.4*10-6 at 90% CL
Take pdg value for d->pipi
Comment: muon fake rate set limit (~10-6)

63. Summary Charm production is an issue at many experiments
Still a very active field on hadron colliders
Important measurements form TEVARTON concerning
- polarisation
- D0 – mixing and CP-Violation
- charmonium production process (color octet model)
- charm fragmentation
Fundamental inputs form HERA-measurements
- charm contribution to structure functions
- charmonium production and polarisation
Input form HERA/TEVATRON needed for LHC
- understanding detector and trigger
- charmonium production important for many measurements in B-Physics programe
- many new inputs expected from LHCb