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Charm Production at HERA and at Hadron-Colliders

This conference discusses charm production, electron-proton interaction, experiments at HERA, TEVATRON, LHC, physics results, D*-production, charm fragmentation, charmonium production, and more. Topics include heavy quark production, parton density functions, quarkonia formation, and proton structure. Key experiments like ZEUS, ATLAS, and LHCb are highlighted, along with the detection methods and physics results. The event covers excited charmed states, rare decays, flavor-changing neutral currents, and the mechanisms of heavy quark production. Join experts in the field to delve into the intricate world of charm physics.

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Charm Production at HERA and at Hadron-Colliders

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  1. Charm Production at HERA and at Hadron-Colliders Quarkonia in Media / Production International Conference Charm 2009 May 20 – 22 2009, Heidelberg, Germany Martin zur Nedden Humboldt-Universität zu Berlin

  2. Content • Charm Production • 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 • 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: • open Charm • 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 Collisions Q g 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 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 PDF

  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 10 - 50

  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 • 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 HERA I: 1994 – 2000 HERA II: 2004 - 2007 H1 Total lumi on tape: ~ 0.5 fb-1 per experiment

  12. The HERA-B Spectrometer 920 GeV protons Spectrometer at the HERA storage ring: proton-fixed target p+A  X , s = 41.6 GeV • 150 M di-lepton trigger events • ~ 300 000 J/ψ • ~ 15 000 c • ~ 5 000 ψ’ • 210 M minimum bias events

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

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

  15. A transverse slice through CMS (LHC)

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

  17. Content • Charm Production • 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 xof 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 F2chas 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 inQ2, 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 • 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 parton scattering cross section (perturbative) fragmentation function (non perturbative) parton density 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 • 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 μ/e+ J/ p μ/e- • 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 μ/e+ J/  p μ/e- (xF) =   c  formation time and length:  = (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 αmeasurement 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/ m+ m- dz Primary vertex • 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 Prompt component: Gaussian J/ from B-meson decay: exponential Combinatorical background

  37. Polarization Effects lab direction Prompt J/ polarized 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. χcProduction of HERA-B 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 • 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) CDF (p-p) 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 HERA-B

  41. Content • Charm Production • 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 • 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 ofJ/ψ→μ+μ-andΥ→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

  48. Tevatron ATLAS 1x106 J/ψ CDF 1.1 fb-1 60 pb-1 4.2x105  D0 1.3 fb-1 85 pb-1 Expected Quarkonia data at early LHC ~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.

  49. Inclusive Differential J/ψcross 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 ~ 25 000 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 octetand 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

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