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QCD in Twenty-One Century

Beam Energy Scan at RHIC - A status report from STAR Nu Xu (1) Nuclear Science Division, Lawrence Berkeley National Laboratory, USA (2) College of Physical Science & Technology, Central China Normal University, China. QCD in Twenty-One Century. Higgs Particle – - Origin of Mass

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QCD in Twenty-One Century

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  1. Beam Energy Scan at RHIC- A status report from STARNu Xu(1) Nuclear Science Division, Lawrence Berkeley National Laboratory, USA(2) College of Physical Science & Technology, Central China Normal University, China

  2. QCD in Twenty-One Century Higgs Particle – - Origin of Mass - SM  The Theory (2) QCD Phase Structure – - Critical point, phase boundaries - Confinement - χC symmetry - Nucleon helicity structure - … - Non-linear QCD at small-x - … - … - Emerging properties of QCD

  3. The QCD Phase Diagram and High-Energy Nuclear Collisions Phase Boundary RHIC,FAIR, NICA TE, Quarkyonic RHIC, SPS, FAIR 3 2 Tini, TC LHC, RHIC 1 1 2 3

  4. Phase diagram: A map shows that, at given degrees of freedom, how matter organize itself under external conditions. Water: H2O The QCDphase diagram: structure of matter with quark- and gluon-degrees (color degrees) of freedom. Phase Diagram: Water

  5. QCD Phase Diagram (2010) K. Fukushima and T. Hatsuda, Rept. Prog. Phys. 74, 014001(2011); arXiv: 1005.4814 Experiments: Systematic measurements (Ebeam, Asize) : extract numbers that are related to the phase diagram

  6. Outline (1) Introduction (2) Recent Results and Beam Energy Scan at RHIC (3) Summary and Outlook

  7. STAR Detectors Fast and Fullazimuthal particle identification EMC+EEMC+FMS (-1 ≤  ≤ 4) MRPC Time Of Flight MTD2013 DAQ1000 *Time Projection Chamber (TPC) *Heavy Flavor Tracker (HFT) 2013 FGT 2011 BNL PAC, 21 - 22, 2010

  8. Particle Identification at STAR TPC ToF TPC STAR TPC K pd π e, μ STAR ToF Log10(p) STAR MTD STAR HFT STAR EMC Neutral particles Strange Jets Heavy Quark hyperons Hadrons Multiple-fold correlations for both HI and Spin physics!

  9. PID: (π±, K±, p) from Au+Au Collisions at 7.7, 39, 200 GeV Au+Au at 7.7 GeV Au+Au at 39 GeV Au+Au at 200 GeV

  10. Polarized p+p program - Study proton intrinsic properties 2020 -eRHIC (eSTAR) STAR Physics Focus Forward program - Study low-x properties, initial condition, search for CGC - Study elastic and inelastic processes in pp2pp 1) At 200 GeV at RHIC - Study medium properties, EoS - pQCD in hot and dense medium 2) RHIC beam energy scan (BES) - Search for the QCD critical point - Chiral symmetry restoration

  11. STAR Di-electron Program Bulk-penetrating probe Reasonable agreement between data and cocktail. No dramatic enhancement in the low mass region: - η, ω, J/ψ from PHENIX - π0, (π±)ϕ, from STAR - ρ contribution not included 2) Topics – the centrality dependence of: - slope parameter vs. mass - v2(pT) vs. mass - RAA(pT) vs. mass - spin-alignment vs. mass ~ 270M events

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

  13. 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!

  14. Comparison with Model Results Small value of specific viscosity over entropy η/s  Model uncertainty dominated by initial eccentricity ε Model: Song et al. arXiv:1011.2783

  15. Low η/s for QCD Matter at RHIC RHIC results 1)η/s ≥ 1/4π 2)η/s(QCD matter) < η/s(QED matter)

  16. Antimatter Discoveries at RHIC April, 2011 March, 2010 “Observation of the Antimatter Helium-4 Nucleus” by STAR Collaboration Nature, 473, 353(2011). “Observation of an Antimatter Hypernucleus” by STAR Collaboration Science, 328, 58(2010).

  17. Light Nuclei Productions at RHIC STAR Experiment: Nature, 473, 353(2011), Top 100 by Discover Magazine • Production rate reduces by a factor of 1.6x103 (1.1x103) for each additional antinucleon added to the antinucleus (nucleus). In high-energy nuclear collisions, N(d) >> N(α): QGP  (anti)light nuclei via coalescence 2) In the Universe, N(d) << N(α): N(anti-α)?

  18. 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

  19. Bulk Properties at Freeze-out • Kinetic Freeze-out: • Central collisions => lower value of • Tkinand larger collectivity β • Little energy dependence. Chemical Freeze-out: - Central collisions => higher values of Tch and μB! - The effect is stronger at lower energy.

  20. Azimuthally Sensitive HBT vs. √sNN Freeze-out eccentricity w.r.t reaction plane: E895: PLB 496 (2000) 1 CERES: PRC 78 (2008) 064901 STAR: PRL 93 (2004) 012301 From √sNN= 2.5 200 GeV, smooth trend observed for the freeze-out eccentricity εf.o., as predicted by the transport model URQMD.

  21. Dynamical Correlations (II)E-by-E PID Yield Ratios Au + Au collisions at RHIC Historical observable: Ratios of identified particle yields. In the observed energy range: √sNN= 7.7 - 200 GeV, both baryon/pion and Strangeness/pion ratios vary smoothly as predicted by the transport model URQMD. No strong enhancement in the strangeness ratio in new data.

  22. Mid-y v1 is sensitive to: • - Nuclear stopping • - The mixture of initial and produced • particles • - Equation of state (EOS) • - L.P. Csernai, D. Rohrich, PLB458, 454(99) • J. Brachmann et al., PRC61, 24909(00) • R. Snellings, et al., PRL84 2803(00) • M. Bleicher and H. Stöcker, PLB526, 309(02) Directed Flow v1 Rapidity y

  23. Mid-y v1 slope vs.√sNN Mid-y v1 is sensitive to: - Nuclear stopping - The mixture of initial and produced particles - Equation of state (EOS) At low beam energy, initial nucleons are dominant, v1 > 0, by definition At higher beam energies, produced particles dominate the dynamics. Due to expansion, the sign of v1 reverses The sign change occurs between √sNN= 7.7 and 11.5 GeV indicating the change in the EOS around these beam energies Transport models can NOT reproduced the trend and change properly

  24. L or B Search for Local Parity Violation in High Energy Nuclear Collisions Parity even observable Voloshin, PR C62, 044901(00). STAR; PRL103, 251601(09); 0909.1717 (PRC). The separation between the same-charge and opposite-charge correlations. - Strong external EM field - De-confinement and Chiral symmetry restoration Future tests with Beam Energy dependence & U+U collisions

  25. Dynamical Correlations STAR Preliminary Below √sNN= 11.5 GeV, the splitting between the same- and opposite-sign charge pairs disappeared If QGP is the source for the observed splitting at high-energy nuclear collisions  hadronic interactions become dominant at √sNN ≤ 11.5 GeV

  26. Observable*: 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!

  27. Particle and Anti-particle v2 vs. √sNN At √sNN ≤ 11.5 GeV: - v2( baryon) > v2(anti-baryon) - v2( π+) < v2(π-) - v2( K-) < v2(K+) Hadronic interactions are dominant STAR: Quark Matter 2011

  28. Sign Dependence and ϕ-meson v2 • The φ v2 falls off trend from other hadrons at 11.5 GeV • The v2-scaling holds for hadrons with same charge (?) • “Effects of Hadronic Potential” byXu, Chen, Ko, Lin, 1201.3391

  29. Susceptibilities and Moments Thermodynamic function: The susceptibility: Conserved Quantum Number S. Gupta, F. Karsch, V. Koch K. Redlich, M. Stephanov … Thermodynamic function  Susceptibility  Moments Model calculations, e.g. LGT, HRG  Measurements

  30. First Results on High Moments STAR: PRL, 105, 22302(2010) Centrality averaged events. In this analysis, effects of volume and detecting efficiencies are all canceled out. Most transport model results values are higher than unity, except the Theminator result at 200GeV. LGT predicted values around 0.8-0.9. Test of thermalization with higher moments. Critical point effect: non-monotonic dependence on collision energy. • STAR: PRL105, 22302(2010) • F. Karsch and K. Redlich, PLB695, 136(2011) Energy Scan in Au+Au collisions: Run 10: 7.7, 11.5, 39 GeV Run 11: 19.6, 27 GeV

  31. Comparing with LGT Results References: - STAR, PRL105, 22303(10) - R.V. Gavai and S. Gupta: PLB696, 459(11) - S. Gupta et al, Science, 332, 1525(2011) • Assumptions: • (a) Freeze-out temperature is close to LGT TC • (b) Thermal equilibrium reached in central collisions • (c) Taylor expansions, at μB≠0, on LGT results are valid • Lattice results are consistent with data for 20 < √sNN < 200 GeV • TC = 175+1-7 (MeV)

  32. Lattice: Phase Transition Temperature

  33. Summary In √sNN= 200GeV Au+Au collisions, hot and dense matter, with partonic degrees of freedom and collectivity, has been formed The matter behavior like a quantum liquid with small η/s (3) Partonic matter antimatter -- =======-- (4) [partonic] < μB ~110–320 (MeV) < [hadronic] (5) More results will come from PID v2 and higher moments. (6) High statistics data for √sNN= 7.7-20 GeV is important.

  34. Outlook: (7.7, 11.5, 15.5, 19.6, 27, 39,62, 200 GeV) • QGP Properties at RHIC • (200 GeV AA and pA Collisions) • Upgrade for HF hadron measurements • di-leptons: v2, pT spectra, RAA, … vs. mass Tini, TC LHC, RHIC TERHIC, SPS, FAIR Phase boundary RHIC,FAIR, NICA 3 2 1 1 2 3 Patonic Matter Hadronic Matter

  35. Thank You!Nu Xu

  36. Atomic Nuclei Formation

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