RHIC能区的集体流和能量扫描

1、1Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14 RHICRHIC能区的集体流和能量扫描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 RHICResults (2): Flow TheorySummaryOutlook2Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14Part I:Flow I

2、ntroduction:3Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14 Elliptic flow v2xzypxpyyxNon-central A+A collisions: azimuthally anisotropic distribution of particles in coordinate-spaceDensity gradients and interactions between the particles: an asymmetry in momentum-spaceSignal is

3、 self-quenching with time early time observable! Measurement: Fourier expansion of the azimuthal angle (-) distributions(mid-rapidity)4Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14Azimuthal DistributionsSystematic measurements as a function of particle mass and taking into acco

4、unt time scalev0Radial flow integrated over evolution v1 Directed flowearlyv2Elliptic flow earlyvn.Fourier Analysis of azimuthal particle distributionv1, v2, vn largest at intermediate impact parameters, zero at b = 0 and b = 2R5Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14Flow

5、 (radial, directed and elliptic)xyxyzxOnly type of transverse flow in central collision (b=0) is radial flow.Integrates pressure history over complete expansion phaseElliptic flow, caused by anisotropic initial overlap region (b 0).More weight towards early stage of expansion.Directed flow, sensitiv

6、e to earliest collision stage (pre-equilibrium, b 0)6Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14RHICv1,v2,v4LHCv1,v2,v4,.and elliptic flow20097Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14Part II:Flow measurements at RHIC:8Y.G.MaWorkshop on RHIC Physics

7、and CSR physics, Weihai, 2009/8/9-14Directed flow at RHICrapidityv1Looking for the wiggle:Directed flow is most sensitive to the initial conditionszx Radial flow 0rapiditypx, v1R. Snellings, H. Sorge, S.V., F. Wang, Nu Xu, PRL 84 (2000) 2803xrapiditypxxBaryon stopping“wiggle”v1 is found being indepe

8、ndent of collision systems.PRL 101, 252301 (2008)9Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14 Longitudinal scaling for v1PHOBOS: Phys. Rev. Lett. 97, 012301 (2006) 1. v10 at mid rapidity and decrease with eta till Ybeam, then turnover at larger eta: probably the proton and nu

9、cl frag dominate identified hadron v1 requested2. The same curve for different size system and energyLimiting fragmentation holds for different energies, collision systems and harmonics.3. No model is successful to reproduce the above scaling: AMPT can only predicted approximate scaling for each col

10、liding species separately. theory to be developed. STAR: Phys. Rev. Lett. 101, 252301 (2008) = - ybeamYmidProton & nucl frag. dominat10Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14Elliptic Flowyxpypxcoordinate-space-anisotropy momentum-space-anisotropyEstablished by geometr

11、y - early timesFirst observed at BEVALAC and at SATURNE11Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14v2 Excitation FunctionRich structure:Transition from in-plane to out-of-plane and back to in-plane emission:Low Ebeam: rotational behavior;Mid Ebeam: squeeze-outHigh Ebeam: pre

12、ssure-induced in-plane emission12Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14STAR, PRL90 032301 (2003)b 4 fm“central” collisionsb 6.5 fmmidcentral collisionsResulting azimuthal distributions13Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14STAR, PRL90 032301

13、 (2003)b 4 fmb 6.5 fmb 10 fmperipheral collisionsResulting azimuthal distributions14Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14STAR, PRL90 032301 (2003)“v2” observed momentum anisotropy is largely elliptic deformation; its amplitude is denoted v2 RHIC v2 reaches large values

14、yielded by hydro (unlike lower energies)Hydrodynamiccalculation ofsystem evolutionElliptic flow15Low pt: mass splittingIdeal hydro can describe the data very well, QGP EoS is a reasonable choiceBlast wave model can also fit the data with a set of four parameters.16Y.G.MaWorkshop on RHIC Physics and

15、CSR physics, Weihai, 2009/8/9-14KET = (mT-m0)/nqPRL. 98, 162301 (2007)1. Number-of-constituent-quark scaling (meson vs baryon)2. v2(pT) /nquark vs. KET/nquark becomes one curve independent of particle species. QuarkMatter2009NCQ scaling in middle Pt17Y.G.MaWorkshop on RHIC Physics and CSR physics, W

16、eihai, 2009/8/9-14Multi-strange particle v2: Partonic CollectivityFinal word on partonic collectivity at RHIC!STAR data (S. Shi et al)PHENIX and p: nucl-ex/0604011v1NQ inspired fit: X. Dong et al. Phy. Let. B 597 (2004) 328-332J. Zuo, J.Y.Chen,X. Cai, YGM, F. Liu et al., EPJC 55,463(2008)18High Pt r

17、egion: non-flow effect, such as partonic Eloss induced correlationSTARDifferent path-length of parton travserse the medium induced Partonic Eloss azimuthal anisotropyData: Au+Au peripheral, dAu, pp similar (left) non-flow correlationDifferent methods to subtract the non-flow effects were developed,

18、such as 4-particle correlationY.G. Ma, Workshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-1419Exploring the non-flow in elliptic flowg0 (hydro dominance), CFB1g1 (jet dominance), CFB0A backwar-forward v2 correlation provides an experimentally accessible observable which distinguish collectiv

19、e and nonflow contribution.Liao&Koch, PRL103 (2009)042302Black solid line: collective flow-only; colored long-dashed: jet-only;Dashed-dotted: weighted contribution (1-g) (black) and g (colored)20Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14QuarkMatter2009Scaling generally h

20、olds in Cu+Cu at 200GeV.Some deviation at more peripheral collisions.phenix preliminaryKET/nq GeV/cKET/nq GeV/cKET/nq GeV/cKET/nq GeV/cKET/nq GeV/cNCQ Scaling in Small System(PHENIX)21Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14NQ roughly works at forward rapidity NCQ Scaling,

21、 Forward RapidityQM09 talk by S. SanderBRAHMS Preliminary22Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14 0 v2, Probe Late Stage Dynamics Long lifetime, balance between daughter rescattering and 0 regeneration.Sensitive to dynamics between chemical and kinetic freeze-out.Signifi

22、cant 0 v2 observed.(n=2, quark level; n=4, hadronic level; preliminary n=4.7 with large error, no conlusion yet)QM09 talk by P. Fachini23Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14Test Hydro in Small System Ideal hydro: P. Huovinen pT 0.5 in dataK=0 in Ideal Hydro, K0.5 in da

23、ta.Boltzmann calculation : Gombeaud and Ollitrault, private communicationPreliminaryPHENIX PreliminaryPHENIX Preliminary33Similar scaling was predicted in Fermi energies: nucleon number scaling & v4/v22 scalingIn hydro by Kolb et al, assuming that quarks have no higher-order anisotropic flowsIf

24、quarks also flow, one getSimilarly, if v4/v2 = for nucleon, then V4/v22(A=2) = +1/2*1/2=1/2V4/v22(A=3) = 1/3+1/3*1/2=1/2This is the case for the right bottom plot!V2/A vs Pt/A&V4/V22 cstV4/A2 vs (Pt/A)2It is interesting to check p, d, t, alpha v2,v4 RHIC!T. Yan, YGM et al., PLB 638 (2006)50 p, d

25、, t, alpha34Light Nuclei v2 at STARBaryon v2 - X.Dong et al, Phys. Lett. B597 (2004) 328BW parameters:F. Retiere, M. Lisa, Phys.Rev. C70 (2004) 044907The 1st observation of negative v2 at RHIC.No model describes the data.d v2 follows A scaling, 3He v2 shows some deviation, need more statistics. = Fi

26、nal state coalescence.35Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14Heavy Q elliptic flow J/ flow : possible test of regeneration Electrons from open c and b semileptonic decays show nonzero elliptic flow J/ regenerated from c quarks should inherit their flowc & b (+ J/) M

27、ain criticisms But then.Absence of J/ elliptic flow would weigh against regeneration models which all predict substantial flow(*) R. ArnaldiQM08(*) F. PrinoHP08PRL 98, 172301 (2007)36Flow of directed photonsRich structure of photon flow (Gale et al., PRL96 (2006) 032302; Chatterjee et al., PRL96, 20

28、2302 (2006)(1)Thermal photons; (2)photons from high Pt parton fragmentation; (3) Bresstrahlung and jet consvertion etcBresstrahlung 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)37Y.G.MaW

29、orkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14Part III:Flow Theory:38Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14Success of ideal hydrodynamicsSuccess of ideal hydrodynamicsIdeal hydrodynamics has correctly reproduced Ideal hydrodynamics has correctly reproduced

30、the collective behaviour at RHIC when pT2 GeV/c.the collective behaviour at RHIC when pT2 GeV/c.Perfect fluid ! sQGP !Perfect fluid ! sQGP !PRL 9292 (2004) 052302How small the values of viscosities will be?How small the values of viscosities will be?To extract viscosities from experimental data, we

31、need viscous hydrodynamics.To extract viscosities from experimental data, we need viscous hydrodynamics.P.F. Kolb and U. Heinz nucl-th/030508439Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14What viscosities will do?Shear viscosity:-The velocity gradient are directly related to v

32、iscous behavior of the fluid-Viscosities reflect resistance to flowBulk viscosity:40Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14Extract /s from experimental data: Extract /s from experimental data: When extract shear viscosity, bulk viscosity is set to be zero.When extract she

33、ar viscosity, bulk viscosity is set to be zero.Should we neglect the bulk viscosity?Should we neglect the bulk viscosity?M. Luzum and P. Romatschke, PRC 7878 (2008) 034915Glauber 0-0.08 ; CGC 0.08-0.16shear viscosity effect on v2 41Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14E

34、quations in causal viscous Equations in causal viscous hydrodynamicshydrodynamicsConservation law:Conservation law:Evolution equations for bulk viscous pressure and shear Evolution equations for bulk viscous pressure and shear pressure tensor:pressure tensor: bulk viscous pressureshear pressure tens

35、orAvoid two problems in the first order theory:Avoid two problems in the first order theory:causality problemcausality probleminstabilitiesinstabilitiesHiscock & Lindblom, PRD 31 31 (1985) 725 Israel & Stewart, Ann.Phys 118118 (1979) 34142Y.G.MaWorkshop on RHIC Physics and CSR physics, Weiha

36、i, 2009/8/9-14- -dissipate to other places at late timedissipate to other places at late time- -smaller relaxation time, larger effects smaller relaxation time, larger effects - -time averaged bulk viscosity is more importanttime averaged bulk viscosity is more importantEfficient large peak leads to

37、 instability?(a) shear viscosity only(b) with bulk viscosity, larger peak, smaller width(c) with bulk viscosity, smaller peak, larger width-decelerate cooling process-decelerate cooling processb=0fm, Au+Aub=0fm, Au+AuJ. W. Li, YGM,G.L. Ma, Chin Phys B (2009)Shear viscosity: Bulk viscosity:Relaxation

38、 times: or2. Central collisions43Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14Viscous v2 suppression:-At low transverse momentum, bulk viscosity will result in -At low transverse momentum, bulk viscosity will result in about 40% additional suppression. This suppression is enhan

39、ced about 40% additional suppression. This suppression is enhanced at larger impact parameter. at larger impact parameter.-bulk viscosity can not be neglected especially at large impact -bulk viscosity can not be neglected especially at large impact parameter.parameter.44Y.G.MaWorkshop on RHIC Physi

40、cs and CSR physics, Weihai, 2009/8/9-14difference about bulk-viscous effect on v2 bulk viscosity effects:(a) Change the flow profile during hydro evolution (b) Additional spectra correction along freeze-out surface Song & Heinz: v2 will decrease, flow corrections only (a), , at freeze-out Monnai

41、 & Hirano: v2 will increase, spectra corrections only(b), ideal hydro for evolution ideal hydro visc. hydro: 20%30%Song & Heinz QM09 talk Monnai & Hirano QM09 talk 45Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14Heavier Q flow Resonance recombination m o d e l + L a

42、n g e v i n s i m u l a t i o n 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)46Charm flow from parton transport modelKo, Lin et al (AMPT)Molnar (MPC)47Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2

43、009/8/9-14Single electron v2 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.Yukinao Akamatsu, Tetsuo Hatsuda, and Tetsufumi Hirano, Phys. Rev. C 79, 054907 (2009)48Y.G.MaWorkshop

44、 on RHIC Physics and CSR physics, Weihai, 2009/8/9-14IV: Summary49V. 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 Thermali

45、zation in partonic level? LHC run50Barrel TOF-MRPC finished for STARrun3run4run5One TOFr Tray with 28 prototype MRPC modules installed in STAR since Oct. 20021/23/45/67/811/129/101/23/45/67/811/129/101/23/45/67/8200620072008Prod. Start40 MRPCs+192 MRPCs+326 MRPCs+326 MRPCs+326 MRPCsAfter STAR Constr

46、uction Readiness Review in April 2006, MRPC mass Production in China started.University of Sci. & Tech. of China (USTC) 1210 (30%*4032) MRPCsOther 70% produced by Tsinghua Univ.51STAR Collaboration is planning for initial beam energy scan in Run 10 (fall 2009) Primary tool: search for anomalousl

47、y large particle identified fluctuations with comprehensive particle identification for charged particles provided by Fully Chinas TOF complete in time for run 10 (fall 2009) 52 Fluctuations and the Critical Point searchData sample 5k events 20 GeV data consistent with systematics observed at SPS Ri

48、se in fluctuations (Kp and g-h) scale roughly with dN/d across energy and centrality consistent with NA49 Ready for the Energy scan Critical point searchLarge acceptance means can do a lot with small amount of dataSTAR Preliminary53Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14A

49、 good tool looking for phase transition at low energy scan: the breaking of NCQ scaling of elliptic flow NCQ scaling for the identified-particle elliptic flow may serve as a probe for searching for critical point. also see F. Lius talk (afternoon)J. Tian, J. H. Chen, Y. G. Ma et. al., Phys. Rev. C 7

50、9, 067901 (2009)54Searching for Flow collapse and wiggle structure-1st phase TransitionH. Stocker55Energy scan of v1 with AMPTJ.Y. Chen, J. X. Zuo, X. Cai, F. Liu, YGM, A. Tang et al., to be submittedAMPT gives larger $v_1$ at low energies than that at high energies, the same trend has been seen in

51、data.The values are underestimated; The different sign of v_1 between pion and proton at low energies can be understood as nucleon shadowing and baryon stopping; when the transverse expansion is strong enough (e.g., at top RHIC energies), it overcomes the bounce-off motion and causes protons to chan

52、ge its sign of directed flow;Hadronic rescattering dose not change much on v1 with the melting version; but large extent with the default version; At Low Ebeam, the default result with short rescattering steps looks reasonable56Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14predicted v2 increase at LHC10% increase in v2 from RHIC to Pb+Pb at LHC is predicted by viscous hydrodynamics.Matthew Luzum and Paul Romatschke, arXiv:0901.4588Hirano et alW. Busza57Y.G.MaWorkshop on RHIC Physics and CSR physics, Weihai, 2009/8/9-14predicted v2 decrease at LHCHYDJET+ Mont