A Brief Tour of RHIC Physics

1. V A Brief Tour of RHIC Physics David Morrison, Physics Dept., BNL

2. Wouldn’t it be fascinating to ... • explore strongly interacting many body physics • shed light on the deconfinement phase transition, chiral phase transition, equation of state, multiparticle correlations, etc. • in short, study QCD matter under extreme conditions

3. pulsar spin-down 1. pulsar slows gradually at first 2. core undergoes phase transition to matter with softer equation of state 3. radius decreases 4. moment of inertia decreases 5. angular velocity increases 6. gradual slowing continues N. Glendenning, astro-ph/9803067

4. early universe 250 RHIC quark-gluon plasma 200 Lattice QCD Chemical Temperature Tch [MeV] SPS 150 AGS deconfinement chiral restoration thermal freeze-out 100 SIS hadron gas 50 neutron stars atomic nuclei 0 0 200 400 600 800 1000 1200 Baryon Potential B [MeV]

5. p+p: no p+A: no Au+Au at 10 GeV/A: yes Pb+Pb at 160 GeV/A: yes Au+Au at sNN = 200 GeV: yes heavy-ion collision: collision of two nuclei, heavy compared to a protons ... relativistic HI: ... at a bombarding energy such that particle production is important

6. First Heavy-Ion Physicist the experiment: a+Au at 2.2 MeV/A the physicists: Geiger and Marsden the result: yep, there’s a nucleus! Ernest Rutherford

7. A+A compared to p+p • less control over detailed kinematics • exclusive reactions not practicable • hadronization and combinatorics • geometry plays important role • time evolution of collision to consider • multiple collisions, rescattering • QCD on top of a semi-classical base

8. cross sections • kilo-barns for ultra-peripheral Au+Au • ~7b for nuclear Au+Au • ~40mb for snn • few mb for sabs(J/Y) • few 100 mb for scc

9. p +p collision UA1, 900 GeV √s = 200, 546, 900 GeV proton anti-proton

10. Au+Au collision √sNN = 130, 200 GeV Gold Gold

11. it doesn’t happen all at once time

12. Spectators Participants Spectators

13. Fixed Target Experiments

17. BNL-AGS/CERN-SPS • strangeness enhancement • systematics of J/Y yields • enhanced yield of intermediate mass vector mesons

18. J/Y systematics J/Y yield peripheral (“p+p”) central (Capella, Ferreiro and Kaidolov, hep-ph/0002300)

20. Collider Experiments

22. PHOBOS BRAHMS PHENIX STAR you are here

23. large acceptance TPC • charged hadrons • hadronic resonances STAR

24. BRAHMS • very forward spectrometer • charged hadrons • coverage to high rapidity

25. PHOBOS • silicon pads, strips • large solid angle • acceptance to very low pT

26. four spectrometers (two for muons) • electrons, hadrons, muons, photons • particle ID out to high pT PHENIX

27. s dependence of RHI physics • BNL-AGS/CERN-SPS (sNN ~ 2-20 GeV) • hard processes practically non-existent • gas of hadronic resonances • RHIC (sNN ~ 200 GeV) • hard processes “abundant” • bulk consistent system in statistical equilibrium • charm at RHICcounterpart of strangeness at SPS • LHC (sNN ~ 10 TeV) • hard processes dominate

28. very (energy) dense matter • gluon saturation • color glass condensate • “classical” chromodynamics • jet quenching and/or annihilation • Debye screening of quarkonium states

29. an experimental broadside 1. Deconfinement R(U) ~ 0.13 fm < R(J/Y) ~ 0.3 fm < R(Y’) ~ 0.6 fm  Electrons, Muons 2. Chiral Symmetry Restoration Mass, width, branching ratio of F to e+e-, K+K- with dM < 5 Mev:  Electrons, Muons, Charged Hadrons DCC’s, Isospin fluctuations:  Photons, Charged Hadrons 3. Thermal Radiation of Hot Gas Prompt g, Prompt g * toe+e-, m+m - :  Photons, Electrons, Muons 4. Strangeness and Charm Production Production of K+, K- mesons:  Hadrons Production of F, J/Y, D mesons:  Electrons, Muons 5. Jet Quenching High pT jet via leading particle spectra:  Hadrons, Photons 6. Space-Time Evolution HBT Correlations of p±p±, K± K±, unlike particles  Hadrons

30. range of estimates for charged particle density  O(1000) charged plus neutral into EMCal acceptance occupancy few %  20-30k channels

31. a word about Au+Au data • PHENIX 350 kB/event; STAR 12 MB/event • raw interaction rate ~1500 Hz • PHENIX: L1 + L2 reduces to 100-200 Hz • record at 30-60 MB/sec • 100’s TB/year

32. 99.5% STAR preliminary (T. Ullrich)

33. chemistry

34. data Hydro central collisions  qualified successes* charged particle distributions elliptic flow Kharzeev & Levin, nucl-th/0108006, PHOBOS data STAR, PRL 86 (2001) 402 *still lacking a truly comprehensive, quantitative description of collisions

35. penetrating probes an analogy: x-rays bring out info invisible at surface; photons, leptons, high pT particles bring info about “core” of colliding system one big difference: at RHIC we also have to create the probes during the collision

36. particle physics “in medium”

37. RAA: yield in Au+Au (per n+n collision) / yield in p+p high pT particles suppressed! superposition of p+p: would expect RAA = 1

38. p0 PHENIX Preliminary 4  pT  6 GeV/c peripheral (“p+p”) central

39. got jets? just need to find them...

40. start by finding a photon ... ||<0.35 PHENIX preliminary 1/Ntrig dN/d • most g come from p0 • find g with E  2.5 GeV • high pTp assoc. with jets • look in cone around g • compare with PYTHIA (p+p) M. Chiu

41. ... or by correlating particles. D. Hardtke

42. the situation today • bulk character largely consistent with chemical, local thermal equilibrium • recent data  era of RHIC hard probes • penetrating probes, wealth of existing data • anticipated data (p+p, d+A) should solidify foundation for comparisons • still, there are many puzzles ...

43. lots of non-pion hadrons at high pT!

44. and so ... • enormous variety of data emerging • appearing very quickly • very consistent • boxing in various pictures of bulk behavior • hard processes, partonic physics now accessible – particle physics in the medium • RHIC is a fantastic place to study QCD, and it’s getting even better

45. some things I didn’t discuss • Hanbury-Brown Twiss (HBT) correlations • balance functions • charge, isospin fluctuations • particle spectra • particle ratios • direct photons • ... and lots else

47. proton-nucleus collisions

48. time

49. 3C58: Quark matter?