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RHIC 能区的集体流和能量扫描

RHIC 能区的集体流和能量扫描. 马余刚 中国科学院上海应用物理研究所 Outline: Flow Introduction Results (1): Flow measurements at RHIC Results (2): Flow Theory Summary Outlook. Y.G.Ma. Workshop on RHIC Physics and CSR physics , Weihai, 2009/8/9-14. Part I: Flow Introduction:. Y.G.Ma.

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RHIC 能区的集体流和能量扫描

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  1. RHIC能区的集体流和能量扫描 马余刚 中国科学院上海应用物理研究所 Outline: • Flow Introduction • Results (1): Flow measurements at RHIC • Results (2): Flow Theory • Summary • Outlook Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  2. Part I: Flow Introduction: Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  3. py y px x y z x Elliptic flow v2 • Non-central A+A collisions: azimuthally anisotropic distribution of particles in coordinate-space • Density gradients and interactions between the particles: an asymmetry in momentum-space • Signal is self-quenchingwith time –early time observable! • Measurement: Fourier expansion of the azimuthal angle (φ-Ψ) distributions (mid-rapidity) Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  4. Azimuthal Distributions Fourier Analysis of azimuthal particle distribution • Systematic measurements as a function of particle mass and taking into account time scale • v0 Radial flow integrated over evolution • v1 Directed flow early • v2 Elliptic flow early • vn …….. v1, v2, vn largest at intermediate impact parameters, zero at b = 0 and b = 2R Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  5. y x y x x z Flow (radial, directed and elliptic) • Only type of transverse flow in central collision (b=0) is radial flow. • Integrates pressure history over complete expansion phase • Elliptic flow, caused by anisotropic initial overlap region (b > 0). • More weight towards early stage of expansion. • Directed flow, sensitive to earliest collision stage (pre-equilibrium, b > 0) Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  6. and elliptic flow 2009 RHIC LHC v1,v2,v4 v1,v2,v4,... Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  7. Part II: Flow measurements at RHIC: Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  8. x x px, v1 x v1 R. Snellings, H. Sorge, S.V., F. Wang, Nu Xu, PRL 84 (2000) 2803 Looking for the ‘wiggle’: rapidity rapidity rapidity z px Baryon stopping Radial flow  <x px> >0 “wiggle” Directed flow at RHIC Directed flow is most sensitive to the initial conditions PRL 101, 252301 (2008) v1 is found being independent of collision systems. Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  9. = η - ybeam Longitudinal scaling for v1 Proton & nucl frag. dominat Ymid PHOBOS: Phys. Rev. Lett. 97, 012301 (2006) STAR: Phys. Rev. Lett. 101, 252301 (2008) • v1~0 at mid rapidity and decrease with eta till Ybeam, then turnover at larger eta: probably the proton and nucl frag dominate  identified hadron v1 requested • The same curve for different size system and energyLimiting fragmentation holds for different energies, collision systems and harmonics. • No model is successful to reproduce the above scaling: AMPT can only predicted approximate scaling for each colliding species separately.  theory to be developed. Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  10. Elliptic Flow coordinate-space-anisotropy ⇔ momentum-space-anisotropy y py px x Established by geometry - early times First observed at BEVALAC and at SATURNE Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  11. v2 Excitation Function Rich structure: Transition from in-plane to out-of-plane and back to in-plane emission: Low Ebeam: rotational behavior; Mid Ebeam: squeeze-out High Ebeam: pressure-induced in-plane emission Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  12. Resulting azimuthal distributions STAR, PRL90 032301 (2003) b ≈ 6.5 fm b ≈ 4 fm “central” collisions midcentral collisions Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  13. Resulting azimuthal distributions STAR, PRL90 032301 (2003) b ≈ 10 fm b ≈ 6.5 fm b ≈ 4 fm peripheral collisions Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  14. “v2” Elliptic flow observed momentum anisotropy is largely elliptic deformation; its amplitude is denoted v2 RHIC v2 reaches large values yielded by hydro (unlike lower energies) STAR, PRL90 032301 (2003) Hydrodynamic calculation of system evolution Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  15. Low pt: mass splitting • Ideal hydro can describe the data very well, QGP EoS is a reasonable choice • Blast wave model can also fit the data with a set of four parameters.

  16. NCQ scaling in middle Pt PRL. 98, 162301 (2007) QuarkMatter2009 KET = (mT-m0)/nq • Number-of-constituent-quark scaling (meson vs baryon) • v2(pT) /nquark vs. KET/nquark becomes one curve independent of particle species. Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  17. Multi-strange particle v2: Partonic Collectivity STAR data (S. Shi et al) PHENIX π and p: nucl-ex/0604011v1 NQ inspired fit: X. Dong et al. Phy. Let. B 597 (2004) 328-332 J. Zuo, J.Y.Chen,X. Cai, YGM, F. Liu et al., EPJC 55,463(2008) Final word on partonic collectivity at RHIC! Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  18. High Pt region: non-flow effect, such as partonic Eloss induced correlation STAR • Different path-length of parton travserse the medium  induced Partonic Eloss  azimuthal anisotropy • Data: Au+Au peripheral, dAu, pp similar (left) non-flow correlation • Different methods to subtract the non-flow effects were developed, such as 4-particle correlation Y.G. Ma, Workshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14

  19. Exploring the non-flow in elliptic flow Liao&Koch, PRL103 (2009)042302 Black solid line: collective flow-only; colored long-dashed: jet-only; Dashed-dotted: weighted contribution (1-g)<v2_F> (black) and g<v2_J> (colored) g0 (hydro dominance), CFB1 g1 (jet dominance), CFB0 A backwar-forward v2 correlation provides an experimentally accessible observable which distinguish collective and nonflow contribution.

  20. NCQ Scaling in Small System(PHENIX) Scaling generally holds in Cu+Cu at 200GeV. Some deviation at more peripheral collisions. KET/nq [GeV/c] KET/nq [GeV/c] KET/nq [GeV/c] phenix preliminary KET/nq [GeV/c] KET/nq [GeV/c] Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14 QuarkMatter2009

  21. NCQ Scaling, Forward Rapidity BRAHMS Preliminary QM09 talk by S. Sander NQ roughly works at forward rapidity Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  22. ρ0 v2, Probe Late Stage Dynamics QM09 talk by P. Fachini Long lifetime, balance between daughter rescattering and ρ0 regeneration. Sensitive to dynamics between chemical and kinetic freeze-out. Significant ρ0 v2 observed. (n=2, quark level; n=4, hadronic level; preliminary n=4.7 with large error, no conlusion yet) Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  23. Test Hydro in Small System Ideal hydro: P. Huovinen • pT < 2 GeV/c • Smaller v2 for heavier hadrons as expected from hydrodynamics. • Sizable v2(Ξ) even in small system • Ideal hydro fails to reproduce the data • Fluctuation of v2? • Viscosity ? • Incomplete thermalization ? STAR preliminary Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  24. Energy Dependence • v2 in Cu + Cu (Au +Au) at 200 and 62.4 GeV are comparable within statistical errors STAR preliminary v2 at Cu + Cu 62.4 GeV ~ 12.5 M events - Same procedure used for 200 GeV. - Event plane resolution is 0.088 ± 0.004 in 0 - 60 %, about factor 2 smaller than that in 200 GeV due to lower multiplicity. STAR Au + Au 200 GeV : PRC77, 054901 (2008) Au + Au 62.4 GeV : PRC75, 054906 (2007) Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  25. System Size Dependence • v2 scaled by eccentricity • Remove the initial geometry effect • v2 seems solely depending • on initial geometry and • number of participant • in 200 GeV collisions • v2∝ v2(ε, Npart) STAR preliminary Au + Au at 200 GeV Au + Au : PRC77, 054901 (2008) Does v2 in most central reach ideal hydrodynamic limit ? Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  26. 45 curves! v2 depends not only by the eccentricity, but also by size the collisions

  27. Centrality dependence of v2 • Partonic transport model can describe the v2(b) • But, a large parton cross section is needed!

  28. Pseudo-rapidity dependence of v2 v2(eta) roughly agrees with scaling proportional to the charged particle density v2(eta-ybeam) scaling in frag region limiting fragmentation picture hydro+afterburner describe v2(eta) well

  29. Ideal Hydro Limit ΞΛp K h± STAR preliminary STAR preliminary Hydro limit STAR preliminary v2/ε scaling: S. Voloshin (for STAR Collaboration), J.Phys.G34(2007)S883 PHENIX π, K and p: nucl-ex/0604011v1 CGC eccentricity: H.J. Drescher and Y. Nara, PRC 76 041903 (2007), H.J. Drescher and Y.Nara, PRC 75 034905 (2007) • Ideal Hydro Limit • Even in central Au + Au collisions, fitting results indicate that the system is still away from hydro limit Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14 Y.G.Ma

  30. most perfect liquid in the world? ; Phys. Rev. Lett. 98, 092301 (2007) Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  31. Effective η/s Extracted from Model STAR preliminary • Data shows particle type dependence, not a built-in feature in the model • Can viscous hydrodynamics explain the particle type dependence ? • Inferred η/s depends strongly on the eccentricity model Caveats: Transport model motivated ~ best for dilute system of massless particles no phase transition T: π spectra slope 200 MeV R: Glauber or CGC calculation H. J. Drescher et al, PRC 76 024905 (2007) Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  32. Boltzmann calculation : Gombeaud and Ollitrault, private communication v4/v22 – An Independent Test PHENIX Preliminary Preliminary v4/v22 ~ 0.5 in Ideal Hydro Borghini & Ollitrault, PLB 642 227 (2006) v4/v22 > 0.5 in data K=0 in Ideal Hydro, K>0.5 in data. PHENIX Preliminary Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  33. Similar scaling was predicted in Fermi energies: nucleon number scaling & v4/v2^2 scaling T. Yan, YGM et al., PLB 638 (2006)50 In hydro by Kolb et al, assuming that quarks have no higher-order anisotropic flows p, d, t, alpha If quarks also flow, one get V2/A vs Pt/A & V4/V2^2 ~ cst V4/A^2 vs (Pt/A)^2 Similarly, if v4/v^2 = ½ for nucleon, then V4/v2^2(A=2) = ¼+1/2*1/2=1/2 V4/v2^2(A=3) = 1/3+1/3*1/2=1/2 This is the case for the right bottom plot! It is interesting to check p, d, t, alpha v2,v4 @ RHIC!

  34. BW parameters: F. Retiere, M. Lisa, Phys.Rev. C70 (2004) 044907 Baryon v2 -- X.Dong et al, Phys. Lett. B597 (2004) 328 Light Nuclei v2 at STAR d v2 follows A scaling, 3He v2 shows some deviation, need more statistics. => Final state coalescence. The 1st observation of negative v2 at RHIC. No model describes the data.

  35. (*) F. Prino@HP08 (**) R. Arnaldi@QM08 Heavy Q elliptic flow PRL 98, 172301 (2007) • J/ψ flow : possible test of regeneration • Electrons from open c and b semileptonic decays show nonzero elliptic flow • J/ψ regenerated from c quarks should inherit their flow c & b (+ J/ψ) • Main criticisms • Flow seen at NA50(*) and NA60(**) where net charm yield is not that high • Indication of other causes that induce J/ψ flow • But then... • Absence of J/ψ elliptic flow would weigh against regeneration models which all predict substantial flow Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  36. Flow of directed photons Rich structure of photon flow (Gale et al., PRL96 (2006) 032302; Chatterjee et al., PRL96, 202302 (2006)) (1)Thermal photons; (2)photons from high Pt parton fragmentation; (3) Bresstrahlung and jet consvertion etc Bresstrahlung photon flow has been also studied in low Ebeam, anti-correlation with proton flow was found. See the following figures. (G. Liu, YGM et al., PLB 663, 312(2008))

  37. Part III: Flow Theory: Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  38. Success of ideal hydrodynamics Perfect fluid ! sQGP ! P.F. Kolb and U. Heinz nucl-th/0305084 PRL 92 (2004) 052302 Ideal hydrodynamics has correctly reproduced the collective behaviour at RHIC when pT<2 GeV/c. How small the values of viscosities will be? To extract viscosities from experimental data, we need viscous hydrodynamics. Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  39. What viscosities will do? Shear viscosity: Bulk viscosity: -The velocity gradient are directly related to viscous behavior of the fluid -Viscosities reflect resistance to flow Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  40. shear viscosity effect on v2 M. Luzum and P. Romatschke, PRC 78 (2008) 034915 Extract η/s from experimental data: Glauber 0-0.08 ; CGC 0.08-0.16 When extract shear viscosity, bulk viscosity is set to be zero. Should we neglect the bulk viscosity? Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  41. bulk viscous pressure shear pressure tensor Equations in causal viscous hydrodynamics Conservation law: Evolution equations for bulk viscous pressure and shear pressure tensor: Avoid two problems in the first order theory: causality problem Israel & Stewart, Ann.Phys 118 (1979) 341 instabilities Hiscock & Lindblom, PRD 31 (1985)725 Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  42. Efficient large peak leads to instability? 2. Central collisions J. W. Li, YGM,G.L. Ma, Chin Phys B (2009) Shear viscosity: (a) shear viscosity only (b) with bulk viscosity, larger peak, smaller width Bulk viscosity: (c) with bulk viscosity, smaller peak, larger width Relaxation times: b=0fm, Au+Au or -decelerate cooling process -dissipate to other places at late time -time averaged bulk viscosity is more important -smaller relaxation time, larger effects Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  43. Viscous v2 suppression: -At low transverse momentum, bulk viscosity will result in about 40% additional suppression. This suppression is enhanced at larger impact parameter. -bulk viscosity can not be neglected especially at large impact parameter. Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  44. (a) Change the flow profile during hydro evolution bulk viscosity effects: (b) Additional spectra correction along freeze-out surface Song & Heinz: v2 will decrease, flow corrections only (a),, at freeze-out Monnai & Hirano: v2 will increase,spectra corrections only(b), ideal hydro for evolution difference about bulk-viscous effect on v2 ideal hydro visc. hydro: 30% 20% Monnai & Hirano QM09 talk Song & Heinz QM09 talk Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  45. Heavier Q flow • Resonance recombination model + Langevin simulation gives good description to spectra and NCQ scaling for phi and J/Psi. L. Ravagli, H. van Hees,* and R. Rapp, Phys. Rev. C 79, 064902 (2009) Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  46. Charm flow from parton transport model Ko, Lin et al (AMPT) Molnar (MPC)

  47. Single electron v2 Yukinao Akamatsu, Tetsuo Hatsuda, and Tetsufumi Hirano, Phys. Rev. C 79, 054907 (2009) • Hirano et.al. can describe RAA but not v2 for single electrons with a relativistic Langevin equation + hydrodynamics. The reason is unclear and it needs further studies. Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  48. IV: Summary • The flow is measured plentifully at RHIC in the past decade, NCQ scaling studied works in lower energy, smaller system and at forward region. • The new matter created at RHIC is the most perfect liquid known so far, which has a small shear viscosity / entropy (close to 1/4π). • When extracting QGP viscosity from experimental data, bulk viscosity effect may not be neglected • The hydro-limit is not saturated by the new matter. • Still a lot needs to be done (both at RHIC and at the LHC) Y.G.Ma Workshop on RHIC Physics andCSR physics, Weihai, 2009/8/9-14

  49. V. Outlook • RHIC detector upgrade will give more precise flow information for identified particles • Beam energy scan: critical phenomena: non-monotonic behavior, or scaling violation of v2/e • U+U collision: larger energy density • Thermalization in partonic level? • LHC run

  50. 2007 2008 2006 1/2 3/4 5/6 7/8 11/12 1/2 3/4 5/6 7/8 1/2 3/4 5/6 7/8 11/12 9/10 9/10 Prod. Start 40 MRPCs +192 MRPCs +326 MRPCs +326 MRPCs +326 MRPCs Barrel TOF-MRPC finished for STAR run5 run4 run3 One TOFr Tray with 28 prototype MRPC modules installed in STAR since Oct. 2002 • After STAR Construction Readiness Review in April 2006, MRPC mass Production in China started. • University of Sci. & Tech. of China (USTC) 1210 (30%*4032) MRPCs • Other 70% produced by Tsinghua Univ.

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