10 12 Degrees in the Shade: The Quark-Gluon Plasma

1. One of greatest challenges in nuclear physics • quantitative understanding of confinement • {quarks, gluons} within a proton, neutron…. artist’s view :) 1012 Degrees in the Shade:The Quark-Gluon Plasma • Progress might be made by deconfining matter • quark-gluon plasma (QGP) • bulk system of many quarks and gluons

2. Quantum Chromodynamics (QCD) t z aQCD strength of coupling at quark-gluon vertex aQCD aQCD multiple exchanges of gluons interaction or scattering ~ | O(a) + O(a2) + O(a3)…|2 quark quark quark quark Strong interaction/scattering by exchange of gluons Craig Ogilvie cogilvie@iastate.edu

3. Coupling Coefficient aQCD a rprobe ~1/(mom. transferred) short distances, a small perturbation theory OK momentum transfer “cloud” of colored gluons surrounds each colored quark a depends on deeply you probe this cloud <momentum transfer> in proton ~ 0.3 GeV • a >~ 1, perturbation calcs catastrophically fail Craig Ogilvie cogilvie@iastate.edu

4. Confinement: A Partial Answer • Attractive interaction grows in strength • try to separate quarks, force pulls them back • More complicated …… try to separate quarks narrow “string” or color field / gluons break, formation of two new quarks pair of hadrons Craig Ogilvie cogilvie@iastate.edu

5. Repellent Vacuum q q Current understanding: correlations between these loops • vacuum condensate “superconducting” • vacuum expels QCD field, narrows the “string” q q • Confinement • force increases as you try to separate quarks • vacuum expels color field • quarks must stay “outside the vacuum” i.e. inside hadrons! “vacuum” is not empty!!, short-lived creation/destruction of particle pairs Craig Ogilvie cogilvie@iastate.edu

6. Change the Surface/ Volume Ratio quark-gluon plasma (QGP) proton • QGP: bulk system of strongly interacting matter • reduced surface/volume • vacuum plays less role in QGP • Grand Scheme ~ >10 years ? • use QGP to learn about non-perturbative QCD • use this knowledge to understand the proton • best way to learn about teeming vacuum Craig Ogilvie cogilvie@iastate.edu

7. Relativistic Heavy-Ion Collider (RHIC) BRAHMS PHOBOS PHENIX STAR Long Island • Two independent accelerator rings • 3.83 km in circumference • Accelerates everything, from p to Au Ös p-p 500 GeV Au-Au 200 GeV Craig Ogilvie cogilvie@iastate.edu

8. Model Calculation of Au+Au Collision Craig Ogilvie cogilvie@iastate.edu

9. STAR Au on Au Event at CM Energy 130 GeV*A Craig Ogilvie cogilvie@iastate.edu

10. 1012 K • Do we reach high enough energy-density to form the QGP ? • Do quarks/gluons re-scatter with each other, often enough to form a thermal system? • Is the matter deconfined quarks and gluons? • Show <10% of RHIC results Craig Ogilvie cogilvie@iastate.edu

11. PHENIX at RHIC • 2 central spectrometers West • 2 forward spectrometers 1st level Trigger John Lajoie, John Hill, Sergei Belikov Heather Farrand, Steve Skutnik TEC (tracking), Marzia Rosati, Sasha Lebedev, Xiaopeng Zong South East North Craig Ogilvie cogilvie@iastate.edu

12. Craig Ogilvie cogilvie@iastate.edu

13. Energy Density Measure energy in the transverse direction near q=90o Zero transverse energy initially => final transverse energy comes from expanding, hot system Craig Ogilvie cogilvie@iastate.edu

14. Determining Energy Density e ~ Et/volume t0, thermalization time, 0.2 to 1 fm/c eBj~ 23.0 GeV/fm3 Lattice ec pR2 eBj~ 4.6 GeV/fm3 Depending on t0, energy density 3 to 15 times larger than needed for QGP (CO chaired paper) QCD prediction 2ct0 PHENIX Et central reactions Craig Ogilvie cogilvie@iastate.edu

15. Interacting Matter => Thermal ? z y x enhanced emission in plane, f~0 and 180 o initial “almond” spatial shape rescattering (John Lajoie chaired paper) Large re-scattering drives initial Spatial anisotropy into a momentum anisotropy if no rescattering, emission random => isotropic distribution Craig Ogilvie cogilvie@iastate.edu

16. Elliptic Flow PHENIX Preliminary Hydro model --- pion --- kaon --- proton Negatives h-,pi-,K-,pbar pt (GeV) • Transfer of position asymmetry to momentum asymmetry • strong scattering • necessary condition for thermal system • reproduced, assuming local equilibrium hydrodynamic QGP Craig Ogilvie cogilvie@iastate.edu

17. Is Matter a Deconfined, Colored Plasma ? Ideal: shine an external probe on a static plasma QGP detectable change in probe probe Possible: use probe created at the same time as plasma is being formed Craig Ogilvie cogilvie@iastate.edu

18. Hard Scattered Parton {Quark or Gluon} hard-scattered parton during Au+Au hadrons have less energy, broader angular spread ? parton loses energy within plasma hard-scattered parton: high pt-transfer, calc. with perturbative QCD cone of hadrons high pt p p Craig Ogilvie cogilvie@iastate.edu

19. Not trivial ! high multiplicity Au+Au => difficult to reconstruct jets Indirect measurement via high pT particles + Craig Ogilvie cogilvie@iastate.edu

20. Energy Loss: Theory parton loses energy within plasma • Many approaches • 1983: Bjorken • …… • 1997: BDMPS- dE/dx depends on path length • 2001: Vitev, Gyulassy, thin plasma • Consensus • radiation of gluons dominates • interference suppresses gluon radiation (LPM effect) • Differences: magnitude, dependence on length, energy…… Craig Ogilvie cogilvie@iastate.edu

21. Null Hypothesis of No Plasma Au impact parameter b num binary collisions Au b (fm) null hypothesis: no new physics beyond proton+proton YieldAuAu = Ncoll * Yieldpp • Low probability of high-pt transfer in a nucleon-nucleon collision • rare hard processes should scale with Ncoll • Ncoll number of binary nucleon-nucleon collisions in Au+Au Craig Ogilvie cogilvie@iastate.edu

22. Ncoll Scaling: Peripheral Au+Au Excellent agreement p0’s from p-p scaled by number of collisions and p0’s from Au-Au peripheral over ~ 5 decades PHENIX Preliminary Craig Ogilvie cogilvie@iastate.edu

23. Suppression at High-pt : Central Collisions PHENIX Preliminary Discovery of new behavior at RHIC • Unusually dense, opaque matter early in collision • Intense theory activity • deconfinement(?) • medium properties(?) Craig Ogilvie cogilvie@iastate.edu

24. Linear Scale: Nuclear Modification Factor RA-Ais called Nuclear Modification Factor At high pT (where hard scattering processes dominate), Null hypothesis RA-A =1 , absence of nuclear effects Craig Ogilvie cogilvie@iastate.edu

25. Suppression on Linear Scale ‘Understood’ enhancement initial state scattering Ncoll baseline • Previous measurements at lower energy accelerators see enhancement, not suppression. • enhancement from random-walk, before hard-scatter • Suppression new @ RHIC Craig Ogilvie cogilvie@iastate.edu

26. Models with QGP are Successful calcs with no QGP calcs with energy-loss in QGP • Quantitative challenge • other factors influence pt spectra • initial state multiple-scattering, “random-walk” • structure functions in Au Craig Ogilvie cogilvie@iastate.edu

27. To Make Progress 2) complementary observable, angular correlations hadrons have less energy, broader angular spread? cone of hadrons increased gluon-radiation within plasma gluon radiation p p CO, Jan Rak Paul Constantin Nathan Grau 1) improve knowledge of baseline, initial scattering d+Au Winter 2002/03 Craig Ogilvie cogilvie@iastate.edu

28. Observation of Jet Cones • Correlation between two-particles • Near-angle enhancement • extract width via Gaussian fit • width of near-side “jet” PHENIX Preliminary  NEAR AWAY • Trigger on high pT particle • Angular distribution other particles wrt trigger Craig Ogilvie cogilvie@iastate.edu

29. Width of Near-Side “Jet” The dashed line (not a fit): constant j=400 MeV. (transverse momentum with respect to “jet” axis) jT Jet Axis pT more central PHENIX Preliminary snear pT (GeV/c) pT (GeV/c) No indication of width broadening vs centrality (?) Craig Ogilvie cogilvie@iastate.edu

30. Hard-Scattering Near Surface cone of hadrons near-angle unchanged back-to-back parton loses so much energy in thick plasma, => no back-to-back correlation remains Craig Ogilvie cogilvie@iastate.edu

31. Back-to-Back Correlation Gone ! STAR Preliminary Au+Au @ 200 GeV/c 0-5% most central 4 < pT(trig) < 6 GeV/c 2 < pT(assoc.) < pT(trig) Strong energy-loss through thick side? Craig Ogilvie cogilvie@iastate.edu

32. Have We Found The QGP @ RHIC ? • e > 5 GeV/fm3, larger than predicted as necessary for QGP • Interacting: strong secondary scattering in collision zone • Colored: energy-loss of scattered partons • Field is cautious • need at least one more confirming signature • Other signatures • J/y: 2003-2004 (Marzia Rosati) • enhanced yield of heavy-mesons, D, B • silicon upgrade • Both sensitive to earliest, hottest stage of the plasma Craig Ogilvie cogilvie@iastate.edu

33. Multi-layer Silicon Vertex Tracker 17 million pixels, 50K strips ISU heading project (CO) BNL, RIKEN, ORNL, LANL, SUNYB,… $5-7 Million Craig Ogilvie cogilvie@iastate.edu

34. Monolithic Pixel Detector charged particle signal electronics n+ • Si wafer combines both sensor and read-out • source of ionization e- : epitaxial layer of chip • amplified, stored in analog memory on each pixel • R&D project Electrical Engineering Profs/students at ISU • epitaxial layer, doping, foundry issues, pixel electronics • First design finished, fabricated, currently being tested Each pixel (50 mm * 400 mm) thickness 150 mm Craig Ogilvie cogilvie@iastate.edu

35. Test-Chip Prof. Gary Tuttle (EE) Tris Tanadi (Masters) Nathan Grau, Hua Pei, Milana Richardson John Hill, CO Craig Ogilvie cogilvie@iastate.edu

36. Progress on QCD Experiment Phenomological Models Dynamics, Energy-loss, hydro… Properties of QGP => QCD Craig Ogilvie cogilvie@iastate.edu

37. Backup Craig Ogilvie cogilvie@iastate.edu

38. Peripheral Fixed p Correlation Function PHENIX PRELIMINARY Kinematically favoured near-angle peak Kinematically disfavoured near-angle peak Craig Ogilvie cogilvie@iastate.edu

39. pQCD parton fragmentation in p-p collisions jT PT jT Trigger PT Jet Jet Pout kT jT transverse momentum with respect to “jet” axis <| jT|> = 400 MeV/c, independent of pTrig for CCOR Collaboration Phys. Lett. 97B, 163 (1980) Craig Ogilvie cogilvie@iastate.edu

40. Increased suppression towards central collisions Craig Ogilvie cogilvie@iastate.edu

41. e+e- Invariant Mass Spectra NJ/Y = 10.8 + 3.2 (stat) + 3.8 - 2.8 (sys) NJ/Y = 5.9 + 2.4 (stat) + 0.7 (sys) • Low statistics, but proof of principle! Craig Ogilvie cogilvie@iastate.edu

42. QGP Phase Change Predicted by Strong Interaction Calculations (Lattice QCD) • Sudden increase in energy density at Tphase change • more degrees of freedom above Tphase change • Tphase change 150-170 MeV • e (QGP) ~2 GeV/fm3 (c.f. e (nucleus) < 1 GeV/fm3) • Shinji Ejiri • hep-lat/0011006 Craig Ogilvie cogilvie@iastate.edu

43. Strength of Interaction Depends on Distance + -r -r -+ -r -+ -+ -r -+ r r e+ e- e+ loops of spin-1 colored gluons coupling stronger at large r polarized loops screen charge coupling weaker at large r ? 1 1/137 r r0=1fm r Craig Ogilvie cogilvie@iastate.edu

44. Rare Processes • Particle production via rare processes should scale with Ncoll , the number of underlying binary nucleon-nucleon collisions • Take scaling with Ncoll as our null hypothesisfor hard processes Craig Ogilvie cogilvie@iastate.edu