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High-Energy Nuclear Collisions and QCD Phase Structure Nu Xu (1) Nuclear Science Division, Lawrence Berkeley National Laboratory, USA (2) College of Physical Science & Technology, Center China Normal University, China. Outline. Introduction - Strong interactions

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  1. High-Energy Nuclear Collisions and QCD Phase StructureNu Xu(1) Nuclear Science Division, Lawrence Berkeley National Laboratory, USA(2) College of Physical Science & Technology, Center China Normal University, China

  2. Outline Introduction - Strong interactions - Phase structure of QCD (2) Selected Results from RHIC - Penetrating probes: Jets and high pT phenomena - Bulk properties: collectivity and thermalization - Beam energy scan: explore the QCD phase structure - Physics of proton spin (3) Summary and Outlook - More discoveries at RHIC - Understand the dynamical evolution from cold nuclear matter to QGP: an Electron-Ion Collider (EIC) at RHIC

  3. Quantum ChromoDynamics Long distance Short distance QCD is the basic theory for strong interaction. Its degrees of freedom, are well defined at short distance. Little is known regarding the dynamical structures of matter that made from q, g. E.g. theconfinement, nucleon spin, the QCD phase structure... Large αS and strong coupling – QCD at long distance.

  4. Confinement Potential • The strong interacting potential between quarks is a function of distance. It also depends on the temperature. • 1) At low temperature, the potential • increases linearly with the distance • between quarks • quarks are confined. • 2) At high temperature, the confinement potential is ‘melted’ • quarks are ‘free’. Note: It is not clear yet at all if there is a critical ‘temperature’ in high energy collisions. V(r,T) T < T conf linear potential constant potential T > T conf r

  5. Lattice QCD Predictions Energy density Heavy quark potential Temperature Distance Left: Large increase in energy density at TC ~ 170 MeV. Not reach the non-interacting S.B. limit. Right: Heavy quark potentials are melted at high temperature. F. Karsch et al. Nucl. Phys. B524, 123(02). Z. Fodor et al, JHEP 0203:014(02). C.R. Allton et al, Phys. Rev. D66, 074507(02). F. Karsch, Nucl. Phys. A698, 199c(02).

  6. Phase Diagram QED QCD Phase Diagram: A map shows that, at given degrees of freedom, how matter organize itself under external conditions.

  7. The QCD Critical Point - LGT prediction on the transition temperature TC is robust. - LGT calculation, universality, and models hinted the existence of the critical point on the QCD phase diagram* at finite baryon chemical potential. - Experimental evidence for either the critical point or 1st order transition is important for our knowledge of the QCD phase diagram*. * Thermalization has been assumed M. Stephanov, K. Rajagopal, and E. Shuryak, PRL 81, 4816(98); K. Rajagopal, PR D61, 105017 (00) http://www.er.doe.gov/np/nsac/docs/Nuclear-Science.Low-Res.pdf

  8. QCD Phase Diagram (1953) RHIC Neutron stars Neutron stars Neutron stars E. Fermi: “Notes on Thermodynamics and Statistics ” (1953)

  9. QCD Phase Diagram 1983 (1, 2, 5-10)ρ0 1983 US Long Range Plan - by Gordon Baym TC~200 MeV (1, 2, 5-10)*ρ0

  10. QCD Phase Diagram (2009) 1983 US Long Range Plan - by Gordon Baym nucl-th: 0907.4489, NPA830,709(09) L. McLerran nucl-th 0911.4806: A. Andronic, D. Blaschke, P. Braun-Munzinger, J. Cleymans, K. Fukushima, L.D. McLerran, H. Oeschler, R.D. Pisarski, K. Redlich, C. Sasaki, H. Satz, and J. Stachel Systematic experimental measurements (Ebeam, A) : Extract numbers that is related to the QCD phase diagram!

  11. PHOBOS BRAHMS RHIC PHENIX STAR AGS TANDEMS Relativistic Heavy Ion ColliderBrookhaven National Laboratory (BNL), Upton, NY v = 0.99995c = 186,000 miles/sec Au + Au at 200 GeV Student Lecture, “Quark Matter 2006”, Shanghai, Nov. 14 - 20, 2006 Animation M. Lisa

  12. STAR Collaboration Student Lecture, “Quark Matter 2006”, Shanghai, Nov. 14 - 20, 2006

  13. STAR Au + Au Collisions at RHIC Peripheral Event Student Lecture, “Quark Matter 2006”, Shanghai, Nov. 14 - 20, 2006 (real-time Level 3)

  14. STAR Au + Au Collisions at RHIC Central Event Student Lecture, “Quark Matter 2006”, Shanghai, Nov. 14 - 20, 2006 (real-time Level 3)

  15. (2) Selected Results from RHIC

  16. Energy Loss in A+A Collisions leading particle suppressed back-to-back jets disappear p+p Au + Au NuclearModification Factor: Student Lecture, “Quark Matter 2006”, Shanghai, Nov. 14 - 20, 2006

  17. Suppression and Correlation In central Au+Au collisions: hadrons are suppressed and back-to-back ‘jets’ are disappeared. Different from p+p and d+Au collisions. Energy density at RHIC:  > 5 GeV/fm3 ~ 300 Parton energy loss: J. Bjorken 1982 (“Jet quenching”) Gyulassy & Wang 1992 …

  18. Hadron Suppression at RHIC Hadron suppression in more central Au+Au collisions!

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

  20. Higher Harmonics Peter Kolb, PRC 68, 031902 • Higher harmonics are expected to be present. For smooth azimuthal distributions the higher harmonics will be small vn ~ v2n/2 • v4 - a small, but sensitive observable for heavy ion collisions. • P. Kolb, PR C68, 031902(04) • v4 - magnitude sensitive to ideal hydro behavior. • Borghini and Ollitrault, nucl-th/0506045 Student Lecture, “Quark Matter 2006”, Shanghai, Nov. 14 - 20, 2006

  21. v2 at Low pT Region P. Huovinen, private communications, 2004 • Minimum bias data! • At low pT, model result fits mass hierarchy well - Collective motion at RHIC • - More work needed to fix the details in the model calculations.

  22.  -mesons Flow: Partonic Flow • -mesons are very special: • they do not re-interact in hadronic environment • they show strong collective flow • they are formed via coalescence with thermal s-quarks • STAR: PRL 99, 112301(2007); Hwaand Yang, nucl-th/0602024; Chen et al., PRC73 (2006) 044903

  23. Collectivity, Deconfinement at RHIC - v2 of light hadrons and multi-strange hadrons - scaling by the number of quarks At RHIC:  mT - NQ scaling  De-confinement PHENIX: PRL91, 182301(03) STAR: PRL92, 052302(04), 95, 122301(05) nucl-ex/0405022, QM05 S. Voloshin, NPA715, 379(03) Models: Greco et al, PRC68, 034904(03) Chen, Ko, nucl-th/0602025 Nonaka et al. PLB583, 73(04) X. Dong, et al., Phys. Lett. B597, 328(04). …. i ii

  24. Partonic Collectivity at RHIC STAR: preliminary QM09: arXiv 0907.2265 Partonic Collectivity at RHIC! Shi: arXiv0907.2265

  25. Results on Anisotropic Flow ALICE arXie1011.3914 From Kuma, Mohanty and Shi Stronger collectivity at LHC! Initial eccentricity ε is largely uncertain

  26. ud ss uud sss Hadron Spectra from RHICp+p and Au+Au collisions at 200 GeV 0-5% more central collisions Multi-strange hadron spectra are exponential in their shapes. STAR white papers - Nucl. Phys. A757, 102(2005).

  27. The Thermal Model • Assume thermally (constant Tch) and chemically (constant ni) equilibrated system at chemical freeze-out • System composed of non-interacting hadrons and resonances • Given Tch and m 's (+ system size), ni's can be calculated in a grand canonical ensemble • Obey conservation laws: Baryon Number, Strangeness, Isospin • Short-lived particles and resonances need to be taken into account

  28. data Thermal model fits Tch = 163 ± 4 MeV B = 24 ± 4 MeV Yields Ratio Results • In central collisions, thermal model fit well with S = 1. The system is thermalized at RHIC. • Short-lived resonances show deviations. There is life after chemical freeze-out. RHIC white papers - 2005, Nucl. Phys. A757, STAR: p102; PHENIX: p184.

  29. Beam Energy Scans at RHIC and LHC Chemical freeze-out (tri-)Critical point LHC: 2.76 – 5.4 TeV (Pb) (0.9 – 14 TeV (p)) RHIC: 200 – 5 GeV (Au) FAiR*/NICA: 11 – 4 GeV (Au) T: 180 – 55 MeV μB: 5 – 800 MeV

  30. ud ss uud sss Hadron Spectra from RHICp+p and Au+Au collisions at 200 GeV 0-5% more central collisions Multi-strange hadron spectra are exponential in their shapes. STAR white papers - Nucl. Phys. A757, 102(2005).

  31. Thermal Model Fits (Blast-Wave) Source is assumed to be: • Locally thermal equilibrated • Boosted in radial direction boosted E.Schnedermann, J.Sollfrank, and U.Heinz, Phys. Rev. C48, 2462(1993) random Extract thermal temperature Tfo and velocity parameter T

  32. Blast Wave Fits: Tfo vs. bT 1) p, K, and p change smoothly from peripheral to central collisions. 2) At the most central collisions, T reaches 0.6c. 3) Multi-strange particles ,  are found at higher Tfo and lower T •  light hadrons move • with higher velocity • compared to strange • hadrons • STAR: NPA715, 458c(03); PRL 92, 112301(04); 92, 182301(04). 200GeV Au + Au collisions

  33. Compare with Model Results 1) Hydro model works well for , K, p 2) Over-predicts flow for multi-strange hadrons 3) Initial ‘collective kick’ introduced(P. Kolb and R. Rapp, PRC67)

  34. Slope Parameter Systematics Partonic Hadronic Student Lecture, “Quark Matter 2006”, Shanghai, Nov. 14 - 20, 2006

  35. Hadronic Partonic • Di-leptons allow us to measure the direct radiation from the matter with partonic degrees of freedom, no hadronization! • Low mass region: • , , e-e+ • minve-e+ • medium effect • Chiral symmetry(?) • -Intermediateregion: • J/e-e+ • minve-e+ • Direct radiation Expanding partonic matter at RHIC and LHC! Direct Radiation Measurements Direct radiation: hadronic partonic

  36. Di-lepton Program atRHIC STAR Preliminary ω ϕ J/ψ pT (GeV/c) Key measurements: yields, mass, RAA, v2 thermalization, thermal rates

  37. Correlations, Susceptibilities, Kurtosis Higher order correlations are correspond to higher power of the correlation length of the system: more sensitive to critical phenomena. M. A. Stephanov, PRL. 102, 032301 (09) • Skewness: Symmetry of the correlation function. • Kurtosis: Peakness of the correlation function. Connection to thermodynamics, X. S & K observables: total charge, total protons, net-p, net-Q R.V. Gavai and S. Gupta: 1001.2796. F. Karsch and K. Redlich, arXiv:1007.2581

  38. High Order Correlations Event by event: net-proton Kurtosis Kp(E)* two proton correlation functions C2(E) ratio of the d/p ratio of K/p * Gavai and Gupta, 03, 05; Gupta 0909.4630 M. Cheng et al. 08 Gupta, Karsch, Stephanov, INT, 08

  39. High Moments: Critical Point Search • Measure conserved quantities, B, s, and Q. • First: High order fluctuation results consistent with thermalization. • First: Tests the long distance QCD predictions in hot/dense medium. • Caveats: (a) static vs. dynamic; (b) net-B vs. net-p; (c) potential effects of freeze-out… • R. Gavai, S. Gupta, 1001. 3796 / F. Karsch, K. Redlich, 1007.2581 / M. Stephanov, 0911.1772. • STAR: PRL105, 02232(2010) and references therein.

  40. Summary and Outlook High-energy nuclear collisions provide a unique tool for studying phase structure of matter,long distance QCD, with partonic degrees of freedom in the laboratory. Next generation new experiments with high rate capabilities are important for the study of the QCD phase structure around the phase boundary: NA61 at SPS, CBM at FAiR and MPD at NICA. Heavy Flavor Measurements: In order to determine the nature of thermalization at high-energy nuclear collisions, a systematic measurements for HF hadrons are necessary. Electron-Ion Collider: In order to understand the dynamical evolution from cold nuclear matter to quark gluon plasmain high-energy nuclear collisions, a good understanding of the initial condition is necessary.

  41. Higgs mass: electro-weak symmetry breaking. (current quark mass) • QCD mass: Chiral symmetry breaking. (constituent quark mass) • Strong interactions do not affect heavy-quark masses. • Important tool for studying properties of the hot/dense medium at RHIC. • Test pQCD predictions at RHIC. Quark Masses Total quark mass (MeV)

  42. PHENIX-VTX: built and installed: c, b physics PHENIC VTX VTX Stripixel layer 4 STAR HFT

  43. HFT: Charm Hadron v2 and RAA • 200 GeV Au+Aum.b. • collisions (500M events). • - Charm hadron collectivity  • light flavor thermalization • Medium properties! • 200 GeV Au+Aum.b. • collisions (|y|<0.5 500M events) • Charm hadron RAA • - Energy loss mechanism! • - QCD in dense medium!

  44. eRHIC (EIC) eRHIC Detector Study the partonic structure of cold nuclear matter at small-x Parton distribution function of nuclear matter Spin structure S. Vigdor: 2010 RHIC operational review injector Coherente-cooler 1) e-ring: 2 SRFLINAC, 1-5 GeV per pass, 4 (6) passes. 2) RHIC:325 GeV p or 130 GeV Au with DX magnets removed. ePHENIX eSTAR

  45. Timeline of QCD and Heavy Ion Facilities Spin STAR FGT Nu Xu, September 2009 BES STAR HFT RHIC-II eSTAR, EIC (eRHIC) Others RHIC US LRP LHC FAIR CBM sis300 NICA J-PARC (50 GeV p+A) JLab(12 GeV upgrade) Spin Heavy Ion R&D Future programs

  46. Many Thanks to the Organizers!Nu Xu

  47. STAR Detector System TPC dE/dx PID: pion/kaon: pT ~ 0.6 GeV/c; proton pT ~ 1.2 GeV/c

  48. Spin varies from rf bucket to rf bucket (9.4 MHz) Spin pattern changes from fill to fill Spin rotators provide choice of spin orientation “Billions” of spin reversals during a fill RHIC pC Polarimeters Absolute Polarimeter (H jet) Siberian Snakes Siberian Snakes PHENIX STAR Spin Rotators (longitudinal polarization) Spin flipper Spin Rotators (longitudinal polarization) Solenoid Partial Siberian Snake Pol. H- Source Helical Partial Siberian Snake LINAC BOOSTER AGS Internal Polarimeter AGS 200 MeV Polarimeter AGS pC Polarimeters Strong Helical AGS Snake Rf Dipole RHIC: Polarized Hadron Collider

  49. ALdetermination: First W Asymmetry Measurement 500 p+p collisions First measurement AL via parity-violation in polarized proton-proton collisions. W+: Observe directly u quark polarization! STAR: PRL, in print. arXiv: 1009.0326

  50. Parity-violating single-spin asymmetry AL for W+/W- STAR Preliminary Run 9 (p+p √s=500 GeV) The First W Asymmetry Result TPC charge separation works up to pT ~ 50GeV Measured asymmetries are in agreement with theory evaluations using polarized pdf’s (DSSV) constrained by polarized DIS data. STAR: PRL, in print. arXiv: 1009.0326

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