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Charm Production Thermalization at RHIC

Charm Production Thermalization at RHIC. Nu Xu Lawrence Berkeley National Laboratory. Many Thanks to Organizers!. X. Dong, H. Huang, H.G. Ritter, K. Schweda, A. Tai, Z. Xu E.L. Bratkovskaya, L. Grandchamp, J. Raufeisen, R. Vogt. Outline. Motivation

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Charm Production Thermalization at RHIC

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  1. Charm Production Thermalization at RHIC Nu Xu Lawrence Berkeley National Laboratory Many Thanks to Organizers! X. Dong, H. Huang, H.G. Ritter, K. Schweda, A. Tai, Z. Xu E.L. Bratkovskaya,L. Grandchamp, J. Raufeisen, R. Vogt

  2. Outline • Motivation • Charm production in p+p and d+Au collisions at RHIC • Charm flow measurements (preliminary) • Summary & Outlook

  3. Equation of State With given degrees of freedom, the EOS - the system response to the changes of the thermal condition - is fixed by its p and T (). Energy density GeV/fm3 • Equation of state: • EOS I : relativistic ideal gas: p = /3 • EOS H: resonance gas: p ~ /6 • EOS Q: Maxwell construction: • Tcrit= 165 MeV, B1/4 = 0.23 GeV • lat=1.15 GeV/fm3 • P. Kolb et al., Phys. Rev. C62, 054909 (2000).

  4. High-Energy Nuclear Collisions jets J/y, D W f X L p, K,K* D, p d, HBT partonic scatterings? early thermalization? Initial Condition - initial scatterings - baryon transfer - ET production - parton dof System Evolves - parton interaction - parton/hadron expansion Bulk Freeze-out - hadron dof - interactions stop Q2 TC Tch Tfo elliptic flow v2 radial flow bT time

  5. Suppression and Correlation In central Au+Au collisions: hadrons are suppressed and back-to-back ‘jets’ are disappeared. Different from p+p and d+Au collisions. Energy density at RHIC:  > 5 GeV/fm3 ~ 300 Parton energy loss: Bjorken 1982 (“Jet quenching”) Gyulassy & Wang 1992 …

  6. Collectivity, Deconfinement at RHIC - v2, spectra of light hadrons and multi-strange hadrons - scaling of the number of constituent quarks At RHIC:  Partonic collectivity has been attained  Deconfinement has has been attained PHENIX: PRL91, 182301(03) STAR: PRL92, 052302(04) S. Voloshin, NPA715, 379(03) Models: Greco et al, PRC68, 034904(03) X. Dong, et al., Phys. Lett. B597, 328(04). ….

  7. QCD Energy Scale mC s-quark mass ~ 0.2 GeV, similar to values of TC critical temperature QCD QCD scale parameter TCH chemical freeze-out temperature  = 4f chiral breaking scale c-quark mass ~ 1.2 - 1.5 GeV >> QCD -- pQCD production - parton density at small-x -- QCD interaction - medium properties Rcc ~ 1/mC => color screening J/ => deconfinement and thermalization u-, d-, s-quarks: light-flavors || c-, b-quarks: heavy-flavors

  8. Why Charm? Charm-quark’s constituent mass is very close to its current mass The value of the charm-quark mass is much higher than the excitation of the system created in high-energy nuclear collisions If open charm-quarks reaches kinetic equilibrium, coalescence process becomes possible for Charmonium formation and open-charm hadrochemistry  Charm-quarks constituent the ideal probe to study the hot-dense medium created at RHIC

  9. J/y via coalescence Grandchamp and Rapp, NPA715, 545(03); hep-ph/0209141(02) J/y: in central AA collisions,due to interaction with light flavors, values of mean pT decrease and yields increase  deconfinement and thermalization for light flavors

  10. Open-/closed-charm hadron yields A. Andronic, P. Braun-Munzinger, K. Redlich, J. Stachel, Phys.Lett. B571 , 36(03). L. Grandchamp and R. Rapp, Phys. Lett. B523 , 60(01). RHIC RHIC (1) open charm cross; (3) medium effects ( properties); (2) direct pQCD production; (4) absorption (color screening) Model results are different, centrality dependence measurements are important!

  11. Charm Measurements PHENIX:Electrons and Muons STAR: Electrons and directly reconstructed Ds

  12. STAR: TPC & MRPC-TOF • A new technology - • Multi-gap Resistive Plate Chamber (MRPC), adopted from CERN-Alice • A prototype detector of time-of-flight (TOFr) was installed in Run3 • One tray: ~ 0.3% of TPC coverage • Intrinsic timing resolution: ~ 85 ps • pion/kaon ID: • pT ~ 1.7 GeV/c • proton ID: • pT ~ 3 GeV/c TPC dE/dx PID: pion/kaon: pT ~ 0.6 GeV/c; proton pT ~ 1.2 GeV/c

  13. D0 direct reconstruction First Direct Open Charm Reconstruction at RHIC STAR Preliminary Event mixing method: C. Adler et al.,Phys. Rev. C66, 061901(R)(2002) H. Zhang, J. Phys. G30, S577(2004)

  14. D mesons measured at STAR STAR Preliminary

  15. STAR TOFr PID Hadron identification: STAR Collaboration, nucl-ex/0309012 electrons Electron identification: TOFr |1/ß-1| < 0.03 TPC dE/dx electrons!!!

  16. Electron Spectra [ c(b) e+x ] STAR Preliminary • An increasing excess found at higher pT region, pT > 1.0 GeV/c, • Expected contribution of semi-leptonic decays from heavy flavor hadrons STAR: nucl-ex/0407006

  17. Consistent in D measurements STAR: nucl-ex/0404029 STAR Preliminary Directly reconstructed D mesons Electrons from D decay D and electron spectra are consistent!

  18. Combining Fits STAR PRL in print Combined fit for D0 and electrons • Good agreement between D0 and electrons spectra! • d+Au and p+p do not show significant nuclear effect PYTHIA: MSEL = 1, CTEQ5M1

  19. Open charm production at RHIC • First reconstructed open charm spectrum at RHIC • - pQCD pT spectra are steeper, total cross section is smaller by a factor of 3-5 • STAR data: PRL in print, nucl-ex/0406007, nucl-ex/0404029 • model results: R. Vogt, 2004

  20. Open charm production at RHIC d/dy  : a factor from model like Pythia. At 200 GeV, the factor 4.7 was used at STAR. A strong dependent on the method of fragmentation in charm pT spectra observed, but not on rapidity distributions. J. Raufeisen and J. Peng, Phys.Rev. D67, 054008(2003) HSD: Phys. Rev. C67 , 054905(2003).

  21. Anisotropy Parameter v2 coordinate-space-anisotropy  momentum-space-anisotropy y py px x Initial/final conditions, EoS, degrees of freedom

  22. Non-photonic electron v2 STAR: 0-80% (F.Laue SQM04) PHENIX: Minimum bias statistical error only HSD: E. Bratkovskaya et al., hep-ph/0409071 X. Dong, S. Esumi, et al., Phys. Lett. B597, 328(2004). corrected for e± from  decay M. Kaneta et al, J.Phys. G30, S1217(04)

  23. Summary • Open charm yields measured in both 200GeV p+p and d+Au collisions. No evidence of deviation from binary collision scaling in d+Au collisions • Perturbative calculations under predicted both yields and spectrum shape. Hadronization process not under control • Study open charm v2 and J/ yields to address thermalization issues at RHIC. • -vertex upgrades Phenix and STAR • - open charm: precision measurements on spectra and v2 • - resonances with both hadronic & leptonic decays

  24. STAR -vertex detector H. Wieman et al., STAR Collaboration

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