Charmonium Production in Media

1. Charmonium Production in Media Quarkonia in Media / Production International Workshop on Heavy Quarkonia 2008 December 2 – 5 2008, Nara Women University, Japan Martin zur Nedden Humboldt-Universität zu Berlin for the HERA-B Collaboration

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

3. Contents • Introduction • HERA-B Detector • J/ψ: Kinematical Distributions • J/ψ: Nuclear Dependence • χc Production

4. Contents: Part 1 • Introduction • HERA-B Detector • J/ψ: Kinematical Distributions • J/ψ: Nuclear Dependence • χc Production

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. Quarkonia Formation Hadronization: formation of Quarkonia (J/ψ, ψ’, χc, Υ) 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

7. 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 wires: based on Glauber-model: a ≠ 1 „dependence”

8. 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

9. Contents: Part 2 • Introduction • HERA-B Detector • J/ψ: Kinematical Distributions • J/ψ: Nuclear Dependence • χc Production

10. HERA-B Detector and Trigger W p-beam C Ti z [cm] Muon-Trigger Electron-Trigger

11. μ+μ- e+e- ~ 120000 J/ψ ~ 2200 ψ′ σJ/ψ ~ 64 MeV ~ 170000 J/ψ ~ 3000 ψ′ σJ/ψ ~ 44 MeV 104 104 J/ψ entries/(30 MeV/c2) entries/(25 MeV/c2) J/ψ 103 103 ψ′ ψ′ 2.5 3.0 3.5 4.0 2.8 3.2 3.6 4.0 m(e+e-)[GeV/c2] m(μ+μ-)[GeV/c2] • 150 M di-lepton trigger events(e+e- / μ+μ-triggers) • ~ 300 000 J/ψ • ~ 15 000 c • ~ 5 000 ψ’ • 210 M minimum bias events Three target materials: pC,pW and pTi collisions HERA-B Data Samples absolute cross section measurements for di-lepton triggered dataneed independent reference cross section measured with minBias events:σ(J/ψ) = (502 ± 44) nb/nucl.

12. Contents: Part 3 • Introduction • HERA-B Detector • J/ψ: Kinematical Distributions • J/ψ: Nuclear Dependence • χc Production

13. J/ pT Distributions 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

14. J/ψ xF - Distribution 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

15. Contents: Part 4 • Introduction • HERA-B Detector • J/ψ: Kinematical Distributions • J/ψ: Nuclear Dependence • χc Production

16. Measurement of Nuclear Dependence nuclear dependence parameter α extracted from the ratio of carbon and tungstenJ/ψ production cross sections Final result form HERA-B: result based on double wire runs only Measurement of the xF and pT dependence of α based on full data sample: Using the measured kinematical distributions of carbon and tungsten (normalized) (full data sample of single and double wire runs)

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

18. Theoretical Models for xF Dependence • Separate description and integration: • final state absorption • interaction with co-movers • energy loss(EL) • shadowing of nuclear PDFs • intrinsic charm quark components (IC) • Initial state energy loss: • Gavin, Milana (GM, Phys.Rev.Lett.68(1992)1834) • based on multiple scattering approach • elastic scatterings of quarks and gluons • Brodsky, Hoyer (BH, Phys.Lett.B298(1993)165) • modification of GM • Nuclear Parton Density Functions: • Eskola, Kolhinen, Salgado (EKS, Eur.Phys.JC9(1999)61) • scale dependence of a proton within a nucleon via DGLAP • initial PDF from CTEQ4L and LO-GRV • Eskola, Paukkunen, Salgado (EPS, arXiv:0802.0139) • improved leading order DGLAP including NLO • Hirai, Kumano, Nagai (HKN, Phys.Rev.C70(2004)044905) • nuclear structure functions and Drell-Yan cross sections • weak anti-shadowing at negative xF Model calculation by R. Vogt: - Phys.Rev.C61(2000)035203 - Phys.Rev.C71(2005)054902 - Private communication

19. Theoretical Descriptions: Overview All calculations done by Ramona Vogt in 2007/2008

20. Nuclear Dependence Measurement: xF average αmeasurement form HERA-B: Final result form HERA-B, to be published in Eur.Phys.J

21. Reggeon Phenomenology Model • Boreskov and Kaidalov (JEPT Lett.D77(2003)599): • predicts anti-screening effects in negative xF region • color less state containing quarks (i.e. D-Mesons) propagates trough the nucleus • large size (consisting of D-mesons), large interaction cross section: energy loss • J/ψ projected out of energy dependent color-less state HERA-B result within uncertainties qualitatively compatible HERA-B E866

22. Contents: Part 5 • Introduction • HERA-B Detector • J/ψ: Kinematical Distributions • J/ψ: Nuclear Dependence • χc Production

23. χcProduction HERA-B: Selection by γ Selection (Eγ) and invariant mass measurement: Relative measurement of χc to J/ψ production • making use of J/ψ production cross section • from min.Bias data • disentangle χc1 and χc2 by double Gaussian fits: • separate cross section measurements • background subtraction by mixed events • separate analysis for electrons and muons • full statistics in both channels: 15000

24. χc 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 electrons muons

25. A-Dependence • Atomic mass number dependence: • same principle as for J/ψ • no significant difference in A-dependence • within the statistical limits averaged result of HERA-B: Δα = 0.05 ± 0.04

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

27. Final Results of χc Final result form HERA-B, accepted for Phys.Rev.D (arXiv:0807.2167)

28. Summary • HERA-B collected 300000 J/, 15000 χc and 220 Mio minimum bias events on nuclear targets (mainly carbon and tungsten) • Final Results on charmonium production: • J/: inclusive production cross section • J/: xF and pT distributions in a new negative xF range • J/: nuclear dependence: tendency of enhancement in at xF <0 • c : production ratio, disentanglement of χc1 and χc2 • Final results on kinematics of J/ production, nuclear dependence of J/ψ and c production are final and published (during 2008)