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Heavy - Flavor Collectivity – Light - Flavor Thermalization at RHIC

This study focuses on the heavy-flavor physics at RHIC, specifically the collectivity of heavy flavor (c, b) quarks and the thermalization of light flavor quarks. The Heavy-Flavor Tracker for STAR is introduced as a tool for measuring the spectra, elliptic flow, and yields of heavy flavor particles to probe the thermalization of light quarks.

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Heavy - Flavor Collectivity – Light - Flavor Thermalization at RHIC

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  1. Heavy-Flavor Collectivity – Light-Flavor Thermalization at RHIC Kai Schweda, Berkeley Lab People: S. Blyth, X. Dong, Y. Lu, M. Oldenburg, H.G. Ritter, A. Rose, A. Shabetai, P. Sorensen, N. Xu, H. Zhang, Y. Zhang.

  2. Outline • Motivation • Heavy-Flavor Physics- Heavy flavor (c,b) collectivity- Charm quark kinetic equilibration • A Heavy-Flavor Tracker for STAR • Summary

  3. Quark Gluon Plasma Source: Michael Turner, National Geographic (1996) • Quark Gluon Plasma: • Deconfined and • thermalized state of quarks and gluons • (?) Can we create a QGP in a controlled mannerto establish its properties

  4. Time Scale deconfinement u-, d-quarks and ‘bound-states’ gain mass Phase and Chiral transitions Plot: N. Xu Coalescence processes occur during (phase) transition and hadronization; u-,d-quarks and ‘bound-states’ gain mass accompanied by expansion; Early thermalization with partons and its duration need to be checked.

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

  6. Collectivity, Deconfinement at RHIC - v2, spectra of light hadrons and multi-strange hadrons - scaling of the number of constituent quarks At RHIC, it seems we have:  Partonic Collectivity • Deconfinement  Thermalization ? • 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. Heavy-Flavor Quarks • Charm(Beauty) quarks dominantly produced in initial collisions • Even in a QGP, charm and beauty quark-mass heavy ! • Charm(Beauty) good probe for medium created at RHIC • If heavy quarks flow:  frequent interactions among all quarks light quarks (u,d,s) likely to be thermalized 106 105 104 103 102 10 1 Mass (MeV/c2) Plot: B. Mueller, nucl-th/0404015. Plot: B. Mueller, nucl-th/0404015.

  8. Charm Elliptic Flow • D  e +X • Sizeable elliptic flow • But: large background:g e+e-p0  e+e-g ... large stat. and syst. uncertainties •  Need direct open charm reconstruction ! M. Kaneta (PHENIX), J. Phys. G: Nucl. Part. Phys. 30, S1217 (2004). F. Laue et al. (STAR), nucl-ex/0411007, (2004).

  9. Open Charm Flow • Two extreme scenarios: • (a) No charm quark flow (PYTHIA) • (b) Charm quark flow (Hydro) •  Differences in D-meson spectra ~30% at pT < 2.0 GeV/c • D  e + X: electron spectra undistinguishable ! • Electron spectrum contains no information on dynamics • Need direct open charm reconstruction to low pT! S. Batsouli et al., Phys. Lett. B 557 (2003) 26.

  10. Open Charm Yields* • No thermal creation of c or b quarks; m(c) = 1.1GeV >> T • c and b quarks interact with lighter quarks  kinetic equilibration ? statistical recombination ? • Ds+ / D0 ratio very sensitive ! • J/y: suppression vs recombination ? D0 = cu Ds+ = cs *A. Andronic et al., Phys. Lett. B571, 36 (2003).

  11. D0 Reconstruction in STAR • D0 p + K, BR = 3.8%, ct = 124mm • calculate invariant mass in p + K system • Peak around 1.86 GeV/c2 • Large combinatorial background •  Large stat. and syst. uncertainties • Need precise track information ! • Need precise pointing device ! TPC only Central Au + Au collisions in STAR

  12. Silicon Vertex            Tracker Magnet Coils E-M Calorimeter Time Projection Chamber Trigger Barrel Electronics Platforms Forward Time Projection Chamber The STAR Detector

  13. The Heavy Flavor Tracker • Two layers • 1.5 cm radius • 5.0 cm radius • 24 ladders • 2 cm by 20 cm • CMOS Sensors • Precise (<10 mm) , thin and low power • 50 mm thick chip + air cooling • 0.36% radiation length • Power budget 100 mW/cm2

  14. D0 p+ + K- Reconstruction Plot: A. Shabetai

  15. Monte Carlo Simulations • Au + Au, 50M central events • D0 K + p • Stat. uncertainties small • Probe charm quark flow ! • Probe light quark thermalization ! Plots: L. Pierpoint and A. Shabetai v2 calcs.: B. Zhang, L.-W. Chen and C.M. Ko, nucl-th/0502056

  16. Summary • Measure spectra, elliptic flow and yields of D0, D, D+s, L+C Probe (u,d,s)-quark thermalization • Need good momentum coverage to low pT !  A Heavy-Flavor Tracker (HFT) for STAR

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