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STAR Physics Focus

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STAR Physics Focus

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  1. Results from RHICBeam Energy Scan-INu Xu(1,2)Outline:1) Introduction2) Selected Results from RHIC BES-I 3)Remarks on Observables in CBM(1) College of Physical Science & Technology, Central China Normal University, China (2) Nuclear Science Division, Lawrence Berkeley National Laboratory, USA

  2. Polarized p+p Program -proton intrinsic properties STAR Decadal Plan + 2020 -eRHIC (eSTAR) Small-x Physics Program - Low-x properties, initial condition, CGC -Elastic and inelastic processes in pp2pp STAR Physics Focus 1) At 200 GeV at RHIC -Deconfinement* &medium properties, EoS - pQCD in hot and dense medium 2) RHICBeam Energy Scan (BES-I) - QCD phase structure*: phase boundary & critical point - Chiral symmetry restoration* * Holy Grail for the physics of high-energy nuclear collisions

  3. STAR Collaboration STAR Experiment

  4. STAR Detector Configurations • STAR: Large coverage, excellent PID, fast DAQ • - detects nearly all particles produced at RHIC • - multiple fold correlation measurements • - Probes: bulk, penetrating, and bulk-penetrating • STAR: Perfect Mid-y Collider Experiment

  5. Particle Identification at STAR TPC TOF TPC TPC K pd π e, μ TOF Log10(p) Charged hadrons Hyperons & Hyper-nuclei MTD HFT Jets EMC Neutral particles Jets & Correlations High pTmuons Heavy-flavor hadrons Multiple-fold correlations from identified particles!

  6. Beam Energy Scan at RHIC Study QCD Phase Structure - Signals of phase boundary - Signals for critical point Observations: (1) Azimuthally HBT 1st order phase transition (2) Directed flow v1 1st order phase transition (3) Dynamical correlations partonic vs. hadronic dof (4) v2 - NCQ scaling partonic vs. hadronic dof (5) Fluctuations Critical point, correl. length - http://drupal.star.bnl.gov/STAR/starnotes /public/sn0493 - arXiv:1007.2613

  7. Bulk Properties at Freeze-out STAR: S. Das, L. Kumar QM2012 • Kinetic Freeze-out: • Central collisions => lower value of • Tkinand larger collectivity β • Stronger collectivity at higher energy Chemical Freeze-out: (GCE) - Central collisions => higher values of Tch and μB! - The effect is stronger at lower energy.

  8. Di-electrons: √sNNDependence STAR: B.C. Huang, P. Huck, QM2012 Chiral symmetry (restoration?) and direct radiations: LMR enhancement vs. collision energy, mass cut dependence Future Heavy Flavor Tracker and Muon Telescope Detector upgrades: - correlated charm contributions - extract direct radiation information

  9. Anisotropy Parameter v2 coordinate-space-anisotropy  momentum-space-anisotropy y py px x Initial/final conditions, EoS, degrees of freedom

  10. Partonic Collectivity at RHIC STAR: preliminary QM09: arXiv 0907.2265 Low pT (≤ 2 GeV/c): hydrodynamic mass ordering High pT (> 2 GeV/c): number of quarks scaling  Partonic Collectivity, necessary for QGP! De-confinement in Au+Au collisions at RHIC!

  11. NCQ Scaling in v2  • m ~ mp ~ 1 GeV • ssφnot K+K-φ • h<< p,  • In the hadronic case, no number • of quark scaling and the value of • v2ofφ will be small. • * Thermalization is assumed!

  12. Collectivity v2 Measurements STAR: NasimMd, S.S. Shi, QM2012 STAR Preliminary Systematic measurements of collectivities At lower beam energies, the number of quark scaling is broken. Hadronic interactions become dominant, especially for √sNN< 11.5 GeV STAR Preliminary

  13. NCQ Scaling of v2/v3 & J/ψ RAA PHENIX: E. O’Brien, QM2012 √sNN≥ 39 GeV, measured vi (i=2,3) and J/ψ RAA show no energy dependence  Partonic interaction and sQGP dominant for collisions at √sNN≥ 39 GeV

  14. L or B Search for Local Parity Violation in High Energy Nuclear Collisions The separation between the same-charge and opposite-charge correlations. - Strong external EM field - De-confinement and Chiral symmetry restoration AAA AA • Parity-even observable, assumptions must be tested • Energy dependence & UU collisions • - S. Voloshin, PRC62, 044901(00). - STAR: PR103, 251601; PRC81, 054908(2009)

  15. Dynamical Correlations vs. √sNN STAR: G. Wang, QM2012 STAR Preliminary SS - OS Below √sNN= 11.5 GeV, the splitting between the same- and opposite-sign charge pairs (SS-OS) disappear If QGP is the source for the observed splitting at high-energy nuclear collisions  hadronic interactions become dominant at √sNN ≤ 11.5 GeV

  16. STAR: G. Wang, QM2012 √sNN= 193GeV U+U Collisions U+U Collisions: (1) test CME with small external B-field (2) test v2 at 30% higher density (3) test path-length dependence of RAA tip-tip body-body Comparing to Au+Au collisions, v2 values are higher in U+U At 1% most central collisions, v2 is found to be finite & SS-OS=0!

  17. Higher Moments 1) High moments for conserved quantum numbers: Q, S, B, in high-energy nuclear collisions 2) Sensitive to critical point (ξ correlation length): 3) Direct comparison with Lattice results: Extract susceptibilities and freeze-out temperature. An independent/important test on thermal equilibrium in heavy ion collisions. - A. Bazavov et al. 1208.1220 (NLOTE) - R.V. Gavai and S. Gupta, PLB696, 459(2011) - S. Gupta, et al., Science, 332, 1525(2011) - STAR Experiment:PRL105, 22303(2010) - M. Stephanov: PRL102, 032301(2009) - F. Karsch et al, PLB695, 136(2011) - M.Cheng et al, PRD79, 074505(2009) - Y. Hatta, et al, PRL91, 102003(2003)

  18. Higher Moment: Net-charge STAR: D. McDonald, QM2012 STAR Preliminary Preliminary net-charge results: efficiency, decay, … effects under study Higher statistics data needed below 20 GeV - HRG Model: K. Redlich et al, private communications

  19. Net-proton Higher Moments BES-II RHIC BES-I STAR: X.F. Luo, QM2012 STAR net-proton results: All data show deviations below Poisson beyond statistical and systematic errors in the 0-5% most central collisions for κσ2 and Sσ at all energies. Larger deviation at √sNN ~ 20GeV UrQMD model show monotonic behavior Higher statistics needed for collisions at √sNN< 20 GeV STAR Preliminary

  20. e-cooling at RHIC for BES-II A. Fedotov, W. Fischer, private discussions, 2012. Fermi Lab Pelletron - Requested to install the e-cooling device - BES-II data taking in 2016 - 2017

  21. RHIC Beam Energy Scan-I Higher Moments Directed Flow v1 Elliptic Flow v2 Jet Quenching Strangeness ET/Nch Freeze-out Changes at √sNN< 20 GeV, calls for higher statistics data!

  22. Exploring the QCD Phase Structure TERHIC, SPS, FAIR 2 Tini, TC LHC, RHIC Phase boundary RHIC,FAIR, NICA 3 1 BES-II Map the QCD Phase Structure HI collisions at √sNN ≤ 20 GeV 1 2 3 Hadronic Matter Partonic Matter • RHIC Top Energy • Study QGP Properties • heavy flavor hadrons • di-leptons • Jets 0 250 500 750 1000 μB (MeV)

  23. Summary BES-I Program: - Partonic QGP dominant: √sNN >39 GeV Hadronic interactions become dominant: √sNN ≤11.5 GeV - High statistics data for energy region √sNN ≤ 20 GeV, needs e-cooling at RHIC => BES-II 2) Jets, Heavy Flavor and Di-lepton Programs: PHENXI: sPHENIX, full jets reconstruction, ready by 2018 STAR: HFT+MTD upgrades, ready by summer of 2014 In the coming decade, RHIC provides unique opportunities for exploring matter with QCD degrees of freedom!

  24. Key Observables for CBM TERHIC, SPS, FAIR 2 Tini, TC LHC, RHIC Phase boundary RHIC,FAIR, NICA 3 1 1 2 SIS300+ IS A MUST! (√sNN ~ 4 - 8.5 GeV, μB ~ 0.7 - 0.4 GeV) Region of extremebaryon density! CBM Key Observables 1) Strangeness production: * phases of the matter, EOS, FO 2) Correlation/fluctuation, light nuclei: * critical point, local-phase-space-density 3) Di-leptons: * space-time-evolution of the matter * Chiral symmetry related properties 3 Hadronic Matter Partonic Matter 0 250 500 750 1000 μB (MeV)

  25. Acknowledgements: • STAR Collaboration • Higher Moments: S. Gupta, F. Karsch, V. Koch, X.F. Luo, L. McLerran, B. Mohanty, K. Rajagopal, K. Redlich, M. Stephanov, H.G. Ritter • Freeze-out & Collectivity: P. Braun-Munzinger, S. Das, U. Heinz, M. Kaneta, D. Keane, L. Kumar, F. Liu, B. Mohanty, H.G. Ritter, A. Schumah, S.S. Shi, S. Voloshin, F.Q. Wang, X.P. Zhang • Strangeness: H.Z. Huang, B. Mohanty,E. Shuryak • Di-lepton & Heavy Flavor: P. Braun-Munzinger, X. Dong, V. Koch, Y.P. Liu, R. Rapp, K. Schweda, J. Stroth, Y.F. Zhang, J. Zhao, P.F. Zhuang

  26. Net-proton Higher Moments STAR:L.Z. Chen, QM2012 STAR Preliminary Higher sensitivity expected from higher order moments STAR first net-proton C6/C2 results, wide centrality bins More data needed especially for collisions below 20 GeV - B. Friman, F. Karsch, K. Redlich, V. Skokov, Eur. Phys. J. C71 1694(2011). - STAR: L.Z. Chen, QM2012

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