1. Axel Drees, University Stony Brook Future Prospects in QCD at High Energy, BNL, July. 21 2006 High T and  QCD in the QCD Lab Era I.The QCD laboratory era Overview Fundamental questions Opportunities with heavy ion collisions II.Key experimental probes and their status Hard probes Electromagnetic radiation III.Roadmap towards the QCD Lab era Burning open questions as of today Detector and accelerator upgrades IV.Well into the QCD lab and the LHC era Jet tomography Quarkonium Low energy program V.RHIC beyond PHENIX and STAR upgrades

2. Axel Drees Fundamental Questions in QCD QCD Laboratory at BNL 2007 2012

3. Axel Drees Long Term Timeline of Heavy Ion Facilities 2006 2012 RHIC 2009 LHC FAIR Phase III: Heavy ion physics QCD Laboratory at BNL PHENIX & STAR upgrades electron cooling “RHIC II” electron injector/ring “e RHIC” RHIC II and STAR/PHENIX upgrades will flourish in QCD Lab era! 2015

4. Axel Drees Exploring the Phase Diagram of QCD Quark Matter: Many new phases of matter Asymptotically free quarks & gluons Strongly coupled plasma Superconductors, CFL …. Experimental access to “high” T and moderate  region: heavy ion collisions Pioneered at SPS and AGS Ongoing program at RHIC Quark Matter Hadron Resonance Gas Nuclear Matter sQGP BB T T C ~170 MeV 940 MeV 1200-1700 MeV baryon chemical potential temperature Mostly uncharted territory Overwhelming evidence: Strongly coupled quark matter produced at RHIC Study high T and r QCD in the Laboratory

5. Axel Drees III. Jet Quenching dN g /dy ~ 1100 I. Transverse Energy central 2% PHENIX 130 GeV Bjorken estimate:   ~ 0.3 fm Quark Matter Produced at RHIC  ~ 10-20 GeV/fm 3 Initial conditions:  therm ~ 0.6 -1.0 fm/c  ~15-25 GeV/fm 3 II. Hydrodynamics PHENIX Huovinen et al V2V2 Pt GeV/c Heavy ion collisions provide the laboratory to study high T QCD!

6. Axel Drees Quark Matter Hadron Resonance Gas Nuclear Matter SIS BB T T C ~170 MeV 940 MeV 1200-1700 MeV baryon chemical potential temperature Fundamental Questions which may find experimental answers using heavy ion collisions! Exploring the QCD phase diagram: What is the nature of a relativistic quantum fluid? What are the relevant degrees of freedom? Is there a critical point? Is there asymptotically free quark matter? Physics at the phase transition: Why are quarks confined in hadrons? Why are hadrons massive and what is the relation to chiral symmetry breaking?

7. Axel Drees Initial state and entropy generation: What is the low x cold nuclear matter phase? How and why does matter thermalize so fast? Related to time evolution of the collision! Fundamental Questions (II)

8. Axel Drees Quark Matter Hadron Resonance Gas Nuclear Matter SIS BB T T C ~170 MeV 940 MeV 1200-1700 MeV baryon chemical potential temperature thermal freeze out chemical freeze out RHIC/BNL LHC/CERN FAIR/GSI Heavy Ion Collisions Provide the Laboratory Different accelerators probe different regions of the phase diagram! Exploring the QCD phase diagram: Is there asymptotically free quark matter? What is the nature of a relativistic quantum fluid? What are the relevant degrees of freedom? Is there a critical point? Physics at the phase transition: Why are quarks confined in hadrons? Why are hadrons massive and what is the relation to chiral symmetry breaking?

9. Axel Drees Initial state and entropy generation: How and why does matter thermalize so fast? What is the low x cold nuclear matter phase? Related to time evolution of the collision! eRHIC FAIR RHIC LHC Heavy Ion Collisions Provide the Laboratory

10. Axel Drees Comparison of Heavy Ion Facilities FAIR  T C RHIC  2 T C LHC 3-4 T C Initial conditions Complementary programs with large overlap: High T: LHC  adds new high energy probes  test prediction based on RHIC data High  : FAIR  adds probes with ultra low cross section RHIC is unique and at “sweet spot” FAIR: cold but dense baryon rich matter fixed target p to U  s NN ~ 1-8 GeV U+U Intensity ~ 2 10 9 /s  ~10 MHz ~ 20 weeks/year RHIC: dense quark matter to hot quark matter Collider p+p, d+A and A+A  s NN ~ 5 – 200 GeV U+U Luminosity ~ 8 10 27 /cm 2 s  ~50 kHz ~ 15 weeks/year LHC: hot quark matter Collider p+p and A+A Energy ~ 5500 GeV Pb+Pb Luminosity ~ 10 27 /cm 2 s  ~5 kHz ~ 4 week/year

11. Axel Drees Key Experimental Probes of Quark Matter Rutherford experiment   atomdiscovery of nucleus SLAC electron scattering e  protondiscovery of quarks penetrating beam (jets or heavy particles) absorption or scattering pattern QGP Nature provides penetrating beams or “hard probes” and the QGP in A-A collisions Penetrating beams created by parton scattering before QGP is formed High transverse momentum particles  jets Heavy particles  open and hidden charm or bottom Calibrated probes calculable in pQCD Probe QGP created in A-A collisions as transient state after ~ 1 fm

12. Axel Drees Hard Probes: Light quark/gluon jets Status Calibrated probe Strong medium effect Jet quenching Reaction of medium to probe (Mach cones, recombination, etc. ) Matter is very opaque Significant surface bias Limited sensitivity to energy loss mechanism Central Au-Au PHENIX preliminary jet hydro vacuum fragmentation reaction of medium

13. Axel Drees Hard Probes: Open Heavy Flavor Status Calibrated probe? Charm follows binary scaling pQCD under predicts cross section by factor 2-5 Strong medium effects Significant charm suppression Significant charm v2 Little room for bottom production Limited agreement with energy loss calculations STAR Preliminary N. Armesto et al, nucl-ex/0511257

14. Axel Drees Hard Probes: Quarkonium Status J/  production is suppressed Similar at RHIC and SPS Consistent with consecutive melting of  and  ’ Consistent with melting J/  followed by regeneration Recent Lattice QCD developments Quarkonium states do not melt at T C Karsch, Kharzeev, Satz, hep-ph/0512239

15. Axel Drees Electromagnetic radiation: No strong final state interaction Carry information from time of emission to detectors Thermal photons and dileptons sensitive to highest temperature of plasma Dileptons sensitive to medium modifications of meson in mixed/hardon phase (only known potential handle on chiral symmetry restoration!) real or virtual photons (lepton pairs) hadron gas: photons low mass lepton pairs QGP: photonsmedium mass e+e+    e-e- q qq e-e- e+e+         e-e- e+e+ q qg  Key Experimental Probes of Quark Matter (II)

16. Axel Drees Electromagnetic Radiation Status First indication of thermal radiation at RHIC Strong modification of meson properties Precision data from NA60 Emerging data from RHIC Theoretical link to chiral symmetry restoration remains unclear NA60

17. Axel Drees “Burning” Open Issues: Jets and heavy quarks Which observables are sensitive to details of energy loss mechanism? How important is collisional energy loss? Do we understand relation between energy loss and energy density? Where are the B-mesons? Which probes are sensitive to the medium and what do they tell us? Quarkonium Is the J/  screened or not? Can we really extract screening length from data? Electromagnetic radiation Can we measure the initial temperature? Is there a quantitative link from dileptons to chiral symmetry resoration? Answers will come from QCD laboratory and LHC

18. Axel Drees Midterm Strategy for RHIC Facility Detectors: Particle identification  reaction of medium to eloss, recombination Displaced vertex detection  open charm and bottom Increased rate and acceptance  Jet tomography, quarkonium, heavy flavors Dalitz rejection  e + e  pair continuum Forward detectors  low x, CGC Accelerator: EBIS  Systems up to U+U Electron cooling  increased luminosity Key measurements require upgrades of detectors and/or RHIC luminosity

19. Axel Drees Dalitz/conversion rejection (HBD) Precision vertex tracking (VTX) PID (k, ,p) to 10 GeV (Aerogel/TOF) High rate trigger (  trigger) Precision vertex tracking (FVTX) Electron and photon measurements Muon arm acceptance (NCC) Very forward (MPC) PHENIX Detector Upgrades at a Glance Central arms: Electron and Photon measurements Electromagnetic calorimeter Precision momentum determination Hadron identification Muon arms: Muon Identification Momentum determination

20. Axel Drees NCC MPC VTX & FVTX -3 -2 -1 0 1 2 3 rapidity  coverage 2  HBD EMCAL (i)  0 and direct  with combination of all electromagnetic calorimeters (ii) heavy flavor with precision vertex tracking with silicon detectors combine (i)&(ii) for jet tomography with  -jet (iii) low mass dilepton measurments with HBD + PHENIX central arms Future PHENIX Acceptance for Hard Probes

21. Axel Drees Full Barrel Time-of- Flight system DAQ and TPC-FEE upgrade Forward Meson Spectrometer Integrated Tracking Upgrade HFT pixel detector Barrel silicon tracker Forward silicon tracker Forward triple- GEM EEMC tracker STAR Upgrades

22. Axel Drees RHIC Upgrades Overview UpgradesHigh T QCDSpin Low x e+e-heavyjetquarkoniaW  G/G flavortomography PHENIX hadron blind detector (HBD)X Vertex tracker (VTX and FVTX)XXOO XO  trigger OX forward calorimeter (NCC) OXO X STAR time of flight (TOF) OXO Heavy flavor tracker (HFT) XOO tracking upgrade OO XO Forward calorimeter (FMS) OX DAQ OXXOOO RHIC luminosity OOXXOOO X upgrade critical for success O upgrade significantly enhancements program

23. Axel Drees Which Measurements are Unique at RHIC? General comparison to LHC LHC and RHIC (and FAIR) are complementary They address different regimes (CGC vs sQGP vs hadronic matter) Experimental issues: “Signals” at RHIC overwhelmed by “backgrounds” at LHC Measurement specific (compared to LHC) Charm measurements: favorable at RHIC Charm is a “light quark” at LHC, no longer a penetrating probe Abundant thermal production of charm Large contribution from jet fragmentation and bottom decay Bottom may assume role of charm at LHC Quarkonium spectroscopy: J/ ,  ’,  c easier to interpreter at RHIC Large background from bottom decays and thermal production at LHC Upsilon spectroscopy can only be done at LHC Low mass dileptons: challenging at LHC Huge irreducible background from charm production at LHC Jet tomography:measurements and capabilities complementary RHIC: large calorimeter and tracking coverage with PID in few GeV range Extended p T range at LHC

24. Axel Drees Signal |  | or  PHENIX <0.35, 1.2-2.4 STAR <1 ALICE <0.9, 2.5-4 CMS <2.4 ATLAS <2.4 J/  →  or ee 440,000220,000390,00040,0008K-100K  ’→  or ee 800040007,000700140-1800  c →  or ee  120,000 *----  →  or ee 140011000**6000800015,000 B → J/  →  ee) 8000250012,900-- D → K  8000****30,000***8,000-- LHC relative to RHIC Luminosity ~ 10% Running time ~ 25% Cross section ~ 10-50x ~ similar yields! Potential improvements with dedicated experiment 4  acceptanceJ/  ’10x  2-10x background rejection  c ???? Note: for B, D increase by factor 10 extends p T by ~3-4 GeV Compiled by T.Frawley * large background ** states maybe not resolved *** min. bias trigger **** pt > 3 GeV There is room for improvement if needed! Quarkonium and Open Heavy Flavor Will be statistics limited at RHIC and LHC!

25. Axel Drees Comments on High p T Capabilities LHC Orders of magnitude larger cross sections ~3 times larger p T range RHIC with current detectors (+ upgrades) Sufficient p T reach Sufficient PID for associated particles What is needed is integrated luminosity! Region of interest for associated particles up to p T ~ 5 GeV

26. Axel Drees Estimates for  -jet Tomography Rapidly falling cross section with rapidity: Assume ~ 1000 events required for statistical  -jet correlation 40x design luminosity ymax  -p T (GeV) 023 121 215 38 Inclusive direct  today Detector + luminosity upgrades Need to extend p T range not obvious! Hadron pid ~ 4 GeV seems sufficient!

27. Axel Drees Low Energy Running at RHIC Physics goals: Search for critical point  bulk hadron production and fluctuations Requires moderate luminosity can maybe be done in next years Chiral symmetry restoration  dilepton production Requires highest possible luminosity, i.e. electron cooling Luminosity estimate with electron cooling Assume 4 weeks of physics each, 25% recorded luminosity and sufficient triggers 20 GeV  10 9 events 2 GeV  10 7 events CERES best run ~ 4x10 7 events NA60 In+In ~ 10 10 sampled events Expected whole vertex minbias event rate [Hz] T. Roser, T. Satogata RHIC Heavy Ion Collisions Increase by factor 100 with electron cooling Very strong low energy dilepton program possible at RHIC

28. Axel Drees Beyond PHENIX and STAR upgrades? Do we need (a) new heavy ion experiment(s) at RHIC? Likely, if it makes sense to continue program beyond 2020 Aged mostly 25 year old detectors Capabilities and room for upgrades most likely exhausted Delivered luminosity leaves room for improvement Nature of new experiments unclear! Specialized experiments 4  multipurpose detector …. “Die Eierlegendewollmilchsau” Key to future planning: First results from RHIC upgrades Detailed jet tomography, jet-jet and  -jet Heavy flavor (c- and b-production) Quarkonium measurments (J/ ,  ’,  ) Electromagnetic radiation (e + e  pair continuum) Status of low energy program Quantitative tests at LHC of models that describe RHIC data Validity of saturation picture Does ideal hydrodynamics really work Scaling of parton energy loss Color screening and recombination New insights and short comings or failures of RHIC detectors will guide planning on time scale 2010-12