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Quantum Chromodynamics

p (uud). meson. p (ud). Baryon. Quantum Chromodynamics. Quantum Chromodynamics (QCD) is the established theory of strong interactions Gluons hold quarks together to from hadrons Gluons and quarks, or partons, typically exist in a color singlet state. Matter Under Extreme Conditions.

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Quantum Chromodynamics

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  1. p(uud) meson p(ud) Baryon Quantum Chromodynamics • Quantum Chromodynamics (QCD) is the established theory of strong interactions • Gluons hold quarks together to from hadrons • Gluons and quarks, or partons, typically exist in a color singlet state

  2. Matter Under Extreme Conditions Nuclei New form of strongly interacting nuclear matter?!

  3. Predictions from QCD: The QGP • Lattice QCD calculations predict a rapid rise in the number of degrees of freedom when T>Tc ~ 150-200 MeV • Quark-Gluon Plasma: A thermally equilibrated state of matter in which quarks and gluons are deconfined from hadrons

  4. Heat is also a window back in time

  5. early universe T RHIC & LHC Quark Matter TC~170MeV (2*1012 K) Hadron Resonance Gas Color Superconductor Nuclear Matter neutron stars mB 940MeV 1200-1700 MeV The QCD Phase Diagram deconfinement & chiral symmetry

  6. BRAHMS PHOBOS RHIC PHENIX STAR Ions: A = 1 ~ 200, pp, pA, AA, AB The Relativistic Heavy Ion Collider Two Superconducting Rings Design PerformanceAu + Aup + p Max snn 200 GeV 500 GeV L [cm-2 s -1 ] 2 x 10261.4 x 1031 Interaction rates 1.4 x 103 s -1 6 x 105 s -1

  7. RHIC acceleration scenario for Au beams

  8. The Solenoidal Tracker at RHIC ( STAR ) Detector

  9. The actual STAR detector opened up

  10. The Time Projection Chamber (TPC) Gas P10 10% methane 90% argon E and B parallel to z axis E 133V/cm B 0.5 Tesla electron drift velocity = 5.45 cm/ms number of x/y pads = 136,608 380 time buckets 100ns/bucket)

  11. Reaction plane x y z cold nuclear matter pNz = 100GeV/c pNT ~200MeV/c Q < 2x10-3 rad The STAR trigger for Au-Au collisions

  12. Au+Au Event Beam view Side view • One reconstructed central Au+Au collision event at GeV • Thousands of produced particles

  13. one “tray”; 120 trays = full acceptance doubles the p range for PID TPC alone TPC and Time of Flight (TOF) Detector Particle Identification (PID) at STAR

  14. - - + Track 1 Decay point Decay point Lambda ( uds ) M = 1.1157 GeV/c2 Anti-Lambda ( uds ) M = 1.1157 GeV/c2 Track 2 Ks  Primary Vertex Primary Vertex DcaV0 mass (GeV/c2) mass (GeV/c2) Decay len DcaImpact Ks and  reconstruction & Topology cuts p+ BR 64% BR 68% Ks and  are V0 particles: decay length: Ks = 2.69 cm  = 7.89 cm In TPC, neutral Ks and  are reconstructed from charged particles: p, K and p (See above sketch). K0S (ds and ds) M = 0.498 GeV/c2 mass (GeV/c2)

  15. STAR Charm Measurement Invariant mass distribution of f meson  For 40~100% centrality bin at |y|<0.5 and 0.4<pt<1.3GeV/c. Red line is the same-event distribution. Black line is the normalized mixed-event distribution. background subtracted D0 D* D± D0

  16. A growing STAR dataset • STAR has recorded >120M Au+Au, >110M Cu+Cu, >35M d+Au events in first five RHIC runs • Improved RHIC performance, increased luminosity • Increased STAR DAQ capabilities * * * Run IVAu+Au 62& 200+++ Run I Au+Au 130 Run IIAu+Aup+p 200 Run IIId+Au200 Run VCu+Cu62 & 200 2002 2004 2006 2000 * pp spin data not included

  17. QGP and hydrodynamic expansion hadronic phase initial state pre-equilibrium hadronization 1 fm/c 2 fm/c 50 fm/c 10 fm/c Experimental results from STAR/RHIC which bear on evidence for the production and properties of the QGP • QCD hard parton scattering,jets • jet-medium interactions • jet quenching (2) Quark recombination/coalescence

  18. Trigger   (1)Jets in nuclear collisions • High-energy hadronic collisions: collisions of constituent partons • Jets can serve as a calibrated probe of dense nuclear matter • “Hard-scattered” outgoing partonsback-to-back in azimuth ()

  19. Initial state Final state Au + Au d + Au p + p Collision systems …

  20. Pedestal&flow subtracted Jets: Modified ( Quenched ) by the medium 4 < pT(trig) < 6 GeV/c pT(assoc) > 2 GeV/c

  21. Jets: Back-to-back reappearance 8 GeV/c < pT(trig) < 15 GeV/c • More stats → higher pT→ Narrow away-side peak emerges in Au+Au!

  22. Trigger-normalized fragmentation function 8 < pT ( trig ) <15 GeV/c Scaling factors Relative to d-Au 0.54 0.25 zT=pT(assoc) / pT(trig)

  23. (2) Elliptic flow v2 and Quark Recombination/Coalescence y py px x y z x • non-central collisions: azimuthal anisotropy in coordinate-space • interactions asymmetry in momentum-space • sensitive to early time in the system’s evolution • Measurement: Fourier expansion of the azimuthal pT distribution

  24. Evolution of Source Shape from Hydrodynamic Model of System Au-Au Collisions sNN = 130 GeV/c Experimental Determination of V2 Distribution of charged particles in azimuthal plane with 2 GeV/c < pT < 6GeV/c. The 0 -10%, 10 – 31%, and 31 – 77% represent different classes of centrality where 0 – 10% Is the most central. In this model the anisotropy in momentum- space measured by v2 is dominated by the early stages

  25. π, K mesons (qq) Elliptic Flow at low pT for Identified Particles p, Λ baryons (qqq) Hydro calculations: Kolb, Heinz and Huovinen - Clear mass dependence, signature of collective flow - Hydrodynamics gives reasonable description of various mass particle at low transverse momenta - Hydro calculation constrained by particle spectra

  26. Elliptic Flow at Intermediate to High pT for Intentified Particles In the pT range 2 GeV/c < pT < 6 GeV/c there is a bifurcation in v2 between mesons (qq ) and baryons ( qqq ). The  is an important test particle since it is a meson ( ss ) but it has a baryonlike mass 1020 MeV/c2

  27. Quark Coalescence: mechanism for hadron formation at intermediate pT

  28. Evidence for Quark Coalescence in Hadron Formation Quark-Number Scaling

  29. SUMMARYIntroduction to talk by Brendt MullerStrange Quark Matter 2006, UCLA March 2006 • Dynamics of energy and momentum tell us that medium produced at RHIC is highly opaque: • Jet quenching / energy loss • Elliptic flow • Valence quark scaling laws tell us that flow is carried by partons • Lattice QCD tells us that flavor quantum numbers are carried by quark-like quasiparticles • “If it flows like a QGP, quenches like a QGP, and looks like a QGP, it probably is a QGP ! But what kind of QGP?

  30. The STAR Collaboration: 51 Institutions, ~ 500 People 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, SINR, 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 Poland: Warsaw University of Technology Russia: MEPHI – Moscow, LPP/LHE JINR – Dubna, IHEP – Protvino Switzerland: University of Bern

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