Charm with STAR Kai Schweda, University of Heidelberg A. Dainese, - PowerPoint PPT Presentation

Charm with STAR Kai Schweda, University of Heidelberg A. Dainese, X. Dong, J. Faivre, Y. Lu, H.G. Ritter, L. Ruan, A. Shabetai, P. Sorensen, N. Xu, H. Zhang, Y. Zhang. 1 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Nuclear phase diagram Energy scan T a k e n f r o m P . S a n g e r 1) RHIC heavy-flavor program / LHC: - Study medium properties at RHIC - pQCD in hot and dense environment 2) RHIC energy scan / GSI program: - Search for the possible phase boundary . - Chiral symmetry restoration Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Outline 1) Introduction 2) Charm production in STAR 3) Heavy − quark collectivity 4) Summary 3 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Heavy flavor in pQCD D mesons Large Q value needed (> ≈ 3GeV) � powerful test for pQCD calculation , Ψ ’, χ R. Vogt Int. J. Mod. Phys. E 12(2003)211 pQCD PDF ccbar 4 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Heavy-Flavor Quarks � Symmetry is broken: 10 6 � QCD dynamical mass Mass (MeV/c 2 ) 10 5 � EW Higgs mass 10 4 10 3 � Even in a QGP, charm and 10 2 beauty quark-mass heavy ! 10 1 � If heavy quarks flow: � frequent interactions among all quarks � light quarks (u,d,s) likely to be thermalized Plot: B. Mueller, nucl-th/0404015. Plot: B. Mueller, nucl-th/0404015. 5 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Charm-quark Elliptic Flow � Coalescence approach � AMPT transport model B. Zhang et al.,PRC 72(2005) 024906. V. Greco et al., PLB 595(2004)202. D = (cu) � Heavy-quark collective flow observable in D-meson v 2 � Large partonic cross sections needed � Frequent interactions � Challenge to theory ? 6 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

The key point is to determine Heavy-Flavor Collectivity Heavy-Flavor Collectivity s , Λ + C , J/ ψ , … D 0 , D ± , D + 7 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Au +Au @ 20, 62, 130, 200 GeV Cu + Cu @ 20, 62, 200 GeV d + Au @ 200 GeV p + p @ 200, 400 GeV Physics of High Baryon Density,Trento, May 29 − June 2, 2006

The STAR Detector Coils � D recon. from hadronic decay channels: TPC (+TOF) � electrons: TPC, TPC+TOF, TPC+EMC � Advantage: Direct D-meson reconstruction large acceptance, | φ | < 2p, | η | < 1.5 9 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Direct Open Charm Reco. STAR: Mixed-event technique benefiting from large acceptance of the TPC → − π + ± 0 → π → π * 0 0 D K ( 3 . 8 %) D D ( 68 %), D K ( 3 . 8 %) s STAR Preliminary A. Tai, QM04 STAR, PRL, 94, 062301 (2005) d+Au 200 GeV 10 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Charm(Bottom) � e − Spectrum � Three independent analyses using different sub-detectors � σ cc = 1.4 ± 0.2 ± 0.4 mb PHENIX, Au+Au: σ cc = 0.62 ± 0.06 ± 0.16 mb � Need direct open charm reconstruction ! (D 0 � K + π ) EMC -- STAR preliminary STAR: PRL 94, 062301 (2005); PHENIX: PRL 94, 082301 (2005). 11 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Heavy-flavor Energy Loss 1.0 Heavy-flavor decay electrons: PHENIX preliminary dN g /dy = 1000 STAR preliminary c and b: L=6fm Probe interaction with medium 0.8 Single Electron R AA (p T ) Rad DGLV only � Induced gluon radiation only 0.6 Rad + elastic BT � Plus elastic collisions 0.4 Rad + elastic TG � Collisional Collisional Energy loss nergy loss 0.2 important, also for l important, also for light ght quarks* ! quarks* ! 0.0 2 3 4 5 6 7 8 9 10 p T (GeV) � Gluon radiation is NOT Gluon radiation is NOT dominant mechanism for dominant mechanism for energy loss ! energy loss ! Calculations: M. Djordjevic et al., nucl-th/0507019; *J. Alam et al., hep-ph/0604131. 12 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Total Charm X − section 1) STAR > pQCD PHENIX >~ pQCD 2) Charm total cross section is a critical reference for J/ ψ suppression/enhanc ement determination. 3) Scales ( μ F and µ R ) may be energy dependent. STAR, PRL, 94, 062301 (2005) R. Vogt, private communication 13 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Total Charm vs Centrality � Total cross section scales with binary collisions � Disrepancy between experiments � pQCD by factor 2 − 3 too low � Charm is a good Charm is a good early stage probe early stage probe ! � Need precise Need precise calibration ! calibration ! 14 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Anisotropy Parameter v 2 coordinate-space-anisotropy ⇔ momentum-space-anisotropy y p y p x x ε = 〈 y 2 − x 2 〉 v 2 = cos2 ϕ , ϕ = tan − 1 ( p y ) 〈 y 2 + x 2 〉 p x Initial/final conditions, EoS, degrees of freedom 15 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Non-photonic electron v 2 c (b) � e + X V. Greco et al. B. Zhang et al. nucl-th/0502056 PLB 595(2004)202 � Large syst. uncertainties due to large background � charm collective flow at p t < 2GeV/c � v 2 (e) favors non-zero v 2 (c) at p T (e)<2 GeV/c. 16 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

J/ ψ Enhancement at RHIC(LHC) � Statistical hadronization ∝ σ cc � strong centrality dependence of J\ ψ yield at LHC � Need total charm yields ! � Measure D Measure D 0 , D , D ± , , Λ c � Probe deconfinement Probe deconfinement and thermalization and thermalization Calculations:P. Braun Munzinger, K. Redlich, and J. Stachel, nucl-th/0304013 . 17 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

J/ ψ at RHIC � Yellow band: allowed range by open charm from STAR and PHENIX � Large uncertainty from open charm cross section ! � Statistical Charm- Statistical Charm- Hadronization might not Hadronization ight not dominate at dominate at RHIC RHIC � Check at LHC… Check at LHC… � Need precise open Need precise open charm reference ! charm reference ! P. Braun-Munzinger et al. 18 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Multiply Heavy-flavored Hadrons � Statistical hadronization - de-confined heavy-quarks - equilibrated heavy-quarks � Enhancement up to x1000 ! Quarks and gluons � hadrons � Measure Ξ cc , Ω cc , B c , ( Ω ccc ) Pb+Pb � Need total charm yields � Probe deconfinement Probe deconfinement and and Ω ccc / D : x1000 thermalization thermalization at LHC t LHC � QGP ! QGP ! p+p F. Becattini, Phys. Rev. Lett. 95, 022301 (2005); P. Braun Munzinger, K. Redlich, and J. Stachel, nucl-th/0304013 . 19 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

D − Meson Pair Correlations � ccbar pair production: DDbar pairs are correlated ! � Here: ∆φ correlation � If charm equili If charm equilibrates brates � correlations vanish ! correlations vanish ! � Influence of hadroni Influence of hadronic scattering (small) ? scattering (small) ? Pythia Calcs.: H. Woehri, priv. comm. Hadronic Transport Model: ∆φ E.L. Bratkovskaya et al., PRC 71 (2005) 044901. 20 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Hadronic Re-scattering � Hadronic re-scattering can not completely wash out DD-correlations � Frequent partonic re-scattering needed � light quark t ght quark thermalization hermalization ! M. Bleicher at al., subm. to Phys. Rev. Lett. 21 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

STAR Detector Upgrade Full Barrel MRPC - TOF Heavy Flavor Tracker • D 0 � K + π, c τ = 123 µ m • Measure decay vertex, σ ≤ 50 µ m • enhance S/B by factor 100 At µ -RHIC: measure Ω elliptic flow! � precise heavy-flavor precise heavy-flavor measurements ! measurements ! Active Pixel Sensors: M. Winter et al., IReS/LEPSI, Strasbourg. 22 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Measure Vector Mesons* Detectors ω φ � φ � e + e - : leptons do not TPC+TOF 8 M 2 M TPC+TOF+SVT+HFT 200K 100K re-scatter � probe the medium at early stage γ � e + e - � Background: γ � e + e - � HFT discriminates background ! � Need low mass detector 23 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Summary � Charm program at RHIC well established � Need precision measurements on spectra, elliptic flow and yields of D 0 , D ± , D +s , Λ + C , J/ ψ � Probe (u,d,s)-quark thermalization � STAR: µ Vertex + full ToF (2008+) 24 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

25 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

26 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

Spectrum coverage 90% 15% σ cc = 1.1 ± 0.1 ± 0.3 mb <p T > ~ 1.3 GeV/c The reconstructed D measurement has much smaller systematic uncertainties in determining the total cross section. 27 Physics of High Baryon Density,Trento, May 29 − June 2, 2006

d + Au � Au + Au STAR Highlight talk Approximately N bin scaling 1.13 ± 0.09 ± 0.42 mb in Au + Au from d+Au to Au+Au! 1.4 ± 0.2 ± 0.4 mb in d + Au As expected --- charm quarks are mostly created from initial NN interactions! 28 Physics of High Baryon Density,Trento, May 29 − June 2, 2006