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Physics of the Heavy Flavor Tracker at STAR Nu Xu Nuclear Science Division Lawrence Berkeley National Laboratory. Outline. Introduction - Recent results from RHIC: R AA and v 2 2) New frontier - heavy quark production - HQ collectivity: test light quark thermalization

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  1. Physics of the Heavy Flavor Tracker at STARNu XuNuclear Science DivisionLawrence Berkeley National Laboratory

  2. Outline Introduction - Recent results from RHIC: RAA and v2 2) New frontier - heavy quark production - HQ collectivity: test light quark thermalization - HQ energy loss: explore pQCD in hot/dense medium 3) Summary

  3. Hadronization and Freeze-out Initial high Q2 interactions Parton matter - QGP - The hot-QCD Initial conditions Experimental approaches: (1) Energy loss - ‘jet-quenching’ (2) Collectivity - v2, radial flow  Heavy Quark productions + (1) and (2) Study the QGP properties at RHIC. Hard scattering production - QCD prediction Interactions with medium - deconfinement/thermalization Initial parton density Initial condition in high-energy nuclear collisions Cold-QCD-matter, small-x, high-parton density - parton structures in nucleon / nucleus High-energy Nuclear Collisions S. Bass

  4. Partonic Energy Loss at RHIC Central Au+Au collisions: hadrons and the away-side jet in back-to-back ‘jets’ are suppressed. Different for p+p and d+Au collisions. Energy density at RHIC:  > 5 GeV/fm3 ~ 300 Explore pQCD in hot/dense medium RAA(C, B) measurements are needed!

  5.  -meson Flow: Partonic Flow “-mesons (and other hadrons) are produced via coalescence of seemingly thermalized quarks in central Au+Au collisions. This observation implies hot and dense matter with partonic collectivity has been formed at RHIC” In order to test early thermalization: v2(pT) of C- and B-hadrons versus pT data are needed!

  6. - Higgs mass: electro-weak symmetry breaking (current quark mass). - QCD mass: Chiral symmetry breaking (constituent quark mass). • Strong interactions do not affect heavy-quark mass. • New scale compare to the excitation of the system. • Study properties of the hot/dense medium. • Explore pQCD at RHIC. Quark Masses Total quark mass (MeV)

  7. Charm Cross Sections at RHIC Large systematic uncertainties in the measurements New displaced, topologically reconstructed measurements for C- and B-hadrons are needed Upgrade

  8. Phenix: PRL 98 172301(07) • HQ decay electron show a non-vanishing v2 • Significant Bottom contributions in HQ decay electrons. • QM2008, India, Feb. 2008 • STAR: A. Mischke, G. Wang • PHENIX: Y. Morino • Need directly topologically reconstructed heavy quark-hadrons!! HQ Decay Electron v2 Results

  9. STAR PRL, 98, 192301 (2007) Heavy Flavor Energy Loss 1) Non-photonic electrons decayed from - charm and beauty hadrons 2) At pT ≥ 6 GeV/c, RAA(n.e.) ~ RAA(h±)! contradicts to naïve pQCD predictions Surprising results - - challenge our understanding of the energy loss mechanism - force us to RE-think about the collisional energy loss - Requiresdirect measurements of C- and B-hadrons.

  10. Decayed Electron pT vs. B- and C-hadron pT Key: Directly reconstructed heavy quark hadrons! Pythia calculation Xin Dong, USTC October 2005

  11. Heavy Flavor Tracker at STAR

  12. STAR Detector MTD MRPC ToF barrel EMC barrel EMC End Cap RPSD FMS F0S PMD FGT: GEM-layers • DAQ1000 • TPC FEE • MTD • Soft  finished HFT: Pixel+IST (+SSD) Heavy Flavor Tracker ongoing

  13. Strategies for Bottom Measurement (1) All Charm states ( D0,±, D*, Ds, C) (1.a) Displaced vertex electrons (TOF+HFT)   (2) Decay to electrons (Charm) (1.a) - (2)   Some Bottom states (Statistics limited at RHIC) Bottom decay electrons Measure Charm and Bottom hadron: Cross sections and Spectra

  14. D0 Reconstruction Efficiency - Central Au+Au collisions: top 10%events. - The thin detector allows measurements down to pT ~ 0.5 GeV/c. - Essential and unique!

  15. NLO pQCD predictions of charm and bottom for the total p+p hadro-production cross sections. Renormalization scale and factorization scale were chosen to be equal. RHIC: 200, 500 GeV LHC: 900, 14000 GeV Ideal energy range for studying pQCD predictions for heavy quark production. Necessary reference for both, heavy ion and spin programs at RHIC. Heavy Quark Production at RHIC RHIC LHC

  16. Charm Hadron v2 Charm-quark flow  Thermalization of light-quarks! Charm-quark does not flow  Drag coefficients - 200 GeV Au+Au minimum biased collisions (500M events). - Charm collectivity  drag/diffusion constants  medium properties!

  17. Charm Hadron RCP QM2008, India, Feb. 2008 STAR: A. Mischke, G. Wang PHENIX: Y. Morino RCP=a*N10%/N(60-80)% • Significant Bottom contributions in HQ decay electrons. • 200 GeV Au+Au minimum biased collisions (|y|<0.5 500M events). • Charm RAA energy loss mechanism, e.g. collisional vs. radiative!

  18. HFT for Di-Electron Measurements Background:  e+e- A low mass detector HFT will be able to measure the heavy quark (HQ) and irreducible physics backgrounds TPC+TOF+HFTA robust di-lepton physics program extending STAR scientific reach

  19. Charm Baryon/Meson Ratios C pK-+ D0 K±-+ 2-body collisions by c and ud 3-body collisions by c, u and d QGP medium QM08 poster: S.H. Lee, K. Ohnoshi, S. Yasui, I.-K. Yoo, and C.M. Ko QM08 summary talk: B. Cole

  20. The Rcb Ratio: pQCD vs. AdS/CFT pQCD pQCD AdS/CFT AdS/CFT WH, M. Gyulassy, to be published • Ratio of Charm over Bottom  separate energy loss mechanism and the limit on (T)/s(T) • At RHIC, AdS/CFT more valid at higher pT due to TRHIC < TLHC W. Horowitz and M. Gyulassy, nucl-th/07062336

  21. PHENIX and STAR Comparison - 2-layer Si hybrid pixels: x/x0 ~ 0.6%; 2.5cm inner radius; fast readout - 2-layer Si strips, x/x0 ~ 2% pT ≤ 2 GeV/c: e± 2 < pT ≤ 6 GeV/c: D-mesons… 1 < pT ≤ 6 GeV/c: B  J/ PHENIX VTX STAR HFT • 2-layer CMOS: x/x0 ~0.28% per layer; • 2.5cm inner radius; 200s integration • 1-layer* Si strips • SSD:x/x0 ~1% • e, D0,±,s,*, c , B… • Low pT > 0.5 GeV/c: v2, RAA • D-D correlation functions

  22. STAR Detectors: 2 Particle Identification EMC TPC TOF HFT FGT

  23. Physics of the Heavy Flavor Tracker at STAR1) The STAR HFT measurements (p+p and Au+Au)(1) Heavy-quark cross sections: D0,±,*, DS, C , B… (2) Both spectra (RAA, RCP) and v2 in a wide pT region: 0.5 - 15 GeV/c (3) Charm hadron correlation functions (4) Full spectrum of the heavy quark hadron decay electrons2) Physics(1) Measure heavy-quark hadron v2, heavy-quark collectivity, to study the medium propertiese.g.light-quark thermalization (2) Measure heavy-quark energy loss to study pQCD in hot/dense mediume.g. energy loss mechanism (3) Measure di-leptions to study the direct radiation from the hot/dense medium (4) Analyze hadro-chemistry including heavy flavors

  24. Projected Run Plan1) First run with HFT: 200 GeV Au+Au v2 and RCP with 500M M.B. collisions2) Second run with HFT: 200 GeV p+p RAA3) Third run with HFT: 200 GeV Au+Au Centrality dependence of v2 and RAA Charm background and first attempt for electron pair measurements C baryon with sufficient statistics

  25. Final Remarks STAR detector + HFT are unique: - Reconstruction of Charm- and Bottom-hadrons directly via hadronic decay in the same detector and at the same time! - Thin detector with 2 PID allows for v2 measurement down to pT ~ 0.5 GeV/c and RAA up to pT ~ 15 GeV/c! - Measure C baryon spectrum! - Utilizes RHIC-II luminosity for the physics program: QGP properties at RHIC energies. - Very exciting world class physics program. - Timely construction, to take advantage of the development of RHIC-II, is crucial for our physics program.

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