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Soft Physics from STAR Bulk properties

Soft Physics from STAR Bulk properties. Fuqiang Wang For the STAR Collaboration. The STAR Detector. Large acceptance: 2 p coverage at mid-rapidity. Magnet Coils Central Trigger Barrel (CTB) ZCal Time Projection Chamber (TPC) Year 2000. Barrel EM Cal (BEMC)

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Soft Physics from STAR Bulk properties

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  1. Soft Physics from STARBulk properties Fuqiang Wang For the STAR Collaboration

  2. The STAR Detector Large acceptance: 2p coverage at mid-rapidity Magnet Coils Central Trigger Barrel (CTB) ZCal Time Projection Chamber (TPC) Year 2000 Barrel EM Cal (BEMC) Silicon Vertex Tracker (SVT)Silicon Strip Detector (SSD) FTPCEndcap EM CalFPD TOFp, TOFr FPD Year 2001+ PMD Soft Physics from STAR

  3. TC≈1708 MeV, eC≈1 GeV/fm3 the Quark-Gluon Plasma The goal: To create and study QGP – a state of deconfined, thermalized quarks and gluons over a large volume predicted by QCD at high energy density. QGP is a bulk, soft physics phenomenon. LatticeQCDprediction: F. Karsch, Prog. Theor. Phys. Suppl. 153, 106 (2004) Questions: • energy density? • degree of thermalization? • deconfinement, DOF, EOS? Tools: - jets & interactions with bulk - elliptic & radial flow - hadron distributions Soft Physics from STAR

  4. outline Courtesy of S. Bass 1 2 3 Initial condition: CGC high-Q2 interactions medium formation hot, dense medium expansion hadronization hadrons hadronic scatterings freeze-out ratios, spectra: freeze-out properties fluctuations, etc. correlations: (1) thermalization? (2) is there conical flow? elliptic flow: does hydro work? what EOS? Soft Physics from STAR

  5. 130 GeV Au+Au: STAR, nucl-ex/0411003. cos(fD), cos(2fD) subtracted correlations. p-p 200 GeV 0.6 < pt < 0.8 GeV/c central Elongation hD by x2.3 unlike-sign correlation Narrowing fD STAR preliminary hD=h1-h2 fD=f1-f2 0.15 < pt < 2 GeV/c real – mixed peripheral hD=h1-h2 fD=f1-f2 parton fragments in pp at low pT. STAR preliminary soft-soft correlations See posters, Prindle (#111), Ray(#87) , Trainor (#31) even at low pt, remnants of jet-like structure survive. strongly coupled to the medium, elongated along h. Soft Physics from STAR

  6. near away Leading hadrons Medium hard-soft interactions Two sources of particles: hard: hard scattering products. soft: bulk medium constituents. Very different as seen in peripheral. Become similar in central. STAR, nucl-ex/0501016. <pT> from away jets Away side <pT> (GeV/c) <pT> from medium decay hard-soft: approach thermalization. soft-soft (larger x-section): higher degree of thermalization. Soft Physics from STAR

  7. Away side <pT> (GeV/c) hard-soft angular correlations pTtrig=4-6 GeV/c pTassoc=0.15-4 GeV/c number correlation pT-weighted correlation See talk, J. Ulery (section 3c) Broader away-side correlations in central Au+Au. Novel dip at p in away <pT> for pTtrig<6 GeV/c. Associated hadrons at p appear more equilibrated. Soft Physics from STAR

  8. correlation functions 4 < pTtrig < 6 GeV/c 1 < pTassoc < 2.5 GeV/c 2.5 < pTtrig < 4 GeV/c 1 < pTassoc < 2.5 GeV/c See talk, J. Ulery (section 3c) and poster, M. Horner (#70) 1/Ntrig dN/d(Df) broad away-side correlations. consistent with flat. - large angle gluon radiation: Vitev - conical flow: Stoecker,Shuryak,Muller - jets deflected by medium flow Df (radian) Soft Physics from STAR

  9. pTtrig=3-4, pTassoc=1-2 GeV/c 2-particle corr, bg, v2 subtracted near near d+Au min-bias Df2 p Dφ2=φ2-φtrig Medium Medium away away 0 0 p mach cone Df1 Au+Au 10% Df2 Dφ2=φ2-φtrig p dN2/dΔφ1dΔφ2/Ntrig 0 deflected jets 0 p Df1 Dφ1=φ1-φtrig conical flow? 3-particle correlation Three regions on away side: center = (p, p) ±0.4 corner = (p+1,p+1) ±0.4 x2 cone = (p+1,p-1) ±0.4 x2 difference in Au+Au average signal per radian2: center – corner = 0.3 ± 0.3 (stat) ± 0.4 (syst) center – cone = 2.6 ± 0.3 (stat) ± 0.8 (syst) d+Au and Au+Au elongated along diagonal: kT effect, and deflected jets? Distinctive features of conical flow are not seen in present data with these pT windows. See talk, J. Ulery (section 3c) Soft Physics from STAR

  10. outline Courtesy of S. Bass 1 2 3 Initial condition: CGC high-Q2 interactions medium formation hot, dense medium expansion hadronization hadrons hadronic scatterings freeze-out ratios, spectra: freeze-out properties fluctuations, etc. correlations: (1) thermalization? (2) is there conical flow? elliptic flow: does hydro work? what EOS? Soft Physics from STAR

  11. PRC 72 (05) 014904 200 GeV Au+Au min-bias Hydro by Huovinen et al. hydro tuned to fit central spectra data. elliptic flow v2 See talks, X. Cai (section 1) M.D. Oldenburg (section 2a) and poster, J. Speltz (#164) large v2 (even f, X, W): strong interactions at early stage large v2 of f, X, W(low hadronic x-sections): partonic collectivity at RHIC. m-dependence: common vT field. hydro works: suggests early thermalization. soft (QGP) EOS favored: sub-hadronic DOF. Soft Physics from STAR

  12. Non-flow effects large at high pT and for lighter systems. multiple methods to remove non-flow: 4-particle cumulants, subtraction of pp. Significantly smaller v2 in Cu+Cu than in Au+Au. Charged hadrons: v2 at 200 GeV in Cu+Cu See talk, G. Wang (section 2a) Soft Physics from STAR

  13. solid: STAR open: PHENIX PRL91(03) constituent quark scaling See talk: Oldenburg (section 2a) - v2 appears to scale with number of constituent quarks. - quark coalescence. Constituent quark DOF. Deconfinement? Soft Physics from STAR

  14. 3<pTtrig<4 GeV/c 0.15<pTassoc<3 GeV/c 3<pTtrig<3.5 GeV/c 1<pTassoc<2 GeV/c • 50% proton • 50% anti-proton • 95% π+ • 95% π- Charged background & v2 not subtracted Df (rad) See talk, J. Ulery (section 3c) hadronization via quark coalescence? Molnar, Voloshin, Ko, Fries, Hwa, et al. explains baryon/meson enhancement NCQ scaling of v2. But no intrinsic angular correlations. No significant difference in angular correlations. More work for coalescence approach. Soft Physics from STAR

  15. outline Courtesy of S. Bass 1 2 3 Initial condition: CGC high-Q2 interactions medium formation hot, dense medium expansion hadronization hadrons hadronic scatterings freeze-out ratios, spectra: freeze-out properties fluctuations, etc. correlations: (1) thermalization? (2) is there conical flow? elliptic flow: does hydro work? what EOS? Soft Physics from STAR

  16. chemical freeze-out hadron-chemistry: particle ratios  chemical freezeout properties Tch short lived resonances STAR white paper Nucl Phys A757 (05) 102 gs • Tch ≈ TC ≈ 165 ± 10 MeVChemical freezeout ≈ hadronization. • s ~ u, d Strangeness is chemically equilibrated. See poster: J. Speltz (#164) Soft Physics from STAR

  17. time and size resonance decays and regeneration: measure kinetic freezeout – life time. HBT: measures freeze-out source sizes (marked by collective flow). Npart Re-scattering and regeneration is needed! Finite time span from chemical to kinetic freeze-out. HBT size (low kT): x2 expansion initial  final in Au+Au. What is the size at chemical freeze-out? may be assessed via p-X correlations. See talks, Z. Chajęcki, P. Chaloupka (section 4a) See talk, S. Salur (section 5a) and posters, C. Markert (#151), D. Mishra (#19) Soft Physics from STAR

  18. W L X strange baryon spectra 200 GeV Au+Au 62.4 GeV Au+Au See talk, S. Salur (section 5a) Soft Physics from STAR

  19. Tch kinetic freeze-out particle spectra  kinetic freezeout properties, total collective radial flow. Blast wave fit See poster, J. Speltz (#164) p,K,p,L: Tkin decreases, b increases with centrality. X, W (low hadronic x-sections): higher Tkin≈Tch, still significant radial flow. Rare particles: kinetic freeze-out ≈ chemical freeze-out ≈ hadronization Soft Physics from STAR

  20. <pt> Fluctuations • STAR Preliminary Au+Au ▲ PHENIX Au+Au ● CERES Pb+Pb 0-5% Most Central Charge conservation corrected (SSC = small scale correlations) event-by-event fluctuations Phase transition  large event-by-event fluctuations See talk, C.A. Pruneau (section 4c) and poster, L. Ray (#87) where is Koch prediction on this graph? • Smooth √s dependence, no threshold effect. • Original QGP signal in inclusive net charge fluctuation is excluded. More differential studies are needed. Soft Physics from STAR

  21. FPD PMD dNch/dh/0.5Npart FTPC STAR preliminary dNp/dh/0.5Npart dNg/dh/0.5Npart STAR preliminary Nucl-ex/0502008 (To appear in PRL) h - ybeam h - ybeam h - ybeam forward physics Forward rapidity at RHIC probes CGC. CGC will be even more important at LHC (and at mid-rapidity). See talk, B. Mohanty (section 1b) • Consistent with the CGC framework. • RdAu-p0 lower than h-: p+ph-is isospin suppressed at large h. • Photons: centrality independent limiting fragmentation. • Charged particles: centrality dependent limiting fragmentation. • Pions follow limiting fragmentation in heavy-ion collisions. Soft Physics from STAR

  22. The Collaboration STAR Summary • New, precision data from STAR. • Jet-medium interaction: • strong indication of thermalization processes • distinctive features of conical flow not seen • Elliptic flow and spectra data show: • early thermalization • partonic collectivity • relevance of constituent quark DOF • Particle distributions with equilibrium models: • chemical freeze-out ≈ hadronization • finite span from chemical to kinetic freeze-out Soft Physics from STAR

  23. STAR The STAR Collaboration U.S. Labs: Argonne, Lawrence Berkeley, and Brookhaven National Labs U.S. Universities: UC Berkeley, UC Davis, UCLA, Caltech, Carnegie Mellon, Creighton, Indiana, Kent State, MIT, MSU, CCNY, Ohio State, Penn State, Purdue, Rice, Texas A&M, UT Austin, Washington, Wayne State, Valparaiso, Yale Brazil: Universidade de Sao Paolo China: IHEP - Beijing, IPP - Wuhan, USTC, Tsinghua, SINAP, IMP Lanzhou Croatia: Zagreb University Czech Republic: Nuclear Physics Institute England: University of Birmingham France: Institut de Recherches Subatomiques Strasbourg, SUBATECH - Nantes Germany: Max Planck Institute – Munich University of Frankfurt India: Bhubaneswar, Jammu, IIT-Mumbai, Panjab, Rajasthan, VECC Netherlands: NIKHEF/Utrecht Poland: Warsaw University of Technology Russia: MEPHI – Moscow, LPP/LHE JINR – Dubna, IHEP – Protvino South Korea: Pusan National University Switzerland: University of Bern Soft Physics from STAR

  24. The Collaboration STAR ---Backup slides--- Soft Physics from STAR

  25. near near 3-4 GeV/c 1-2 GeV/c Df2 assoc trigger soft bkgd assoc Medium Medium away away mach cone Df1 Df2 deflected jets Df1 Is there conical flow? See talk, J. Ulery (section 3c) 3-particle correlation hard-soft-corr + soft-bkgd. flow modulated background: soft-soft-corr in underlying event. Soft Physics from STAR

  26. existing v2 scaling data Soft Physics from STAR

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