Recreating the Birth of the Universe

1. Recreating the Birth of the Universe T.K HemmickUniversity at Stony Brook W.A. Zajc

2. The Beginning of Time • Time began with the Big Bang: • All energy (matter) of the universe concentrated at a single point in space and time. • The universe expanded and cooled up to the present day: • ~3 Kelvin is the temperature of most of the universe. • Except for a few “hot spots” where the expanding matter has collapsed back in upon itself. • How far back into time can we explain the universe based upon our observations in the Lab? • What Physics do we use to explain each stage? Thomas K Hemmick

3. Evolution of the Universe Universe Expands and Cools Gravity…Newtonian/General Relativity Too hot for quarks to bind!!! Quark Plasma…Standard Model Physics Too hot for nuclei to bind Hadronic Gas—Nuclear/Particle Physics Nucleosynthesis builds nuclei up to Li Nuclear Force…Nuclear Physics Universe too hot for electrons to bind E-M…Atomic (Plasma) Physics Thomas K Hemmick

4. Decoding the Analogy Thomas K Hemmick

5. Electric vs. Color Forces • Electric Force • The electric field lines can be thought of as the paths of virtual photons. • Because the photon does not carry electric charge, these lines extend out to infinity producing a force which decreases with separation., • Color Force • The gluon carries color charge, and so the force lines collapse into a “flux tube”. • As you pull apart quarks, the energy in the flux tube becomes sufficient to create new quarks. • Trying to isolate a quark is as fruitless as trying to cut a string until it only has one end! CONFINEMENT Thomas K Hemmick

6. What about this Quark Soup? • If we imagine the early state of the universe, we imagine a situation in which protons and neutrons have separations smaller than their sizes. • In this case, the quarks would be expected to lose track of their true partners. • They become free of their immediate bonds, but they do not leave the system entirely. • They are deconfined, but not isolated • similar to water and ice, water molecules are not fixed in their location, but they also do not leave the glass. Thomas K Hemmick

7. Phase Diagrams Nuclear Matter Water Thomas K Hemmick

8. Making Plasma in the Lab • Extremes of temperature/density are necessary to recreate the Quark-Gluon Plasma, the state of our universe for the first ~10 microseconds. • Density threshold is when protons/neutrons overlap • 4X nuclear matter density = touching. • 8X nuclear matter density should be plasma. • Temperature threshold should be located at “runaway” particle production. • The lightest meson is the pion (140 MeV/c2). • When the temperature exceeds the mc2 of the pion, runaway particle production ensues creating plasma. • The necessary temperature is ~1012 Kelvin. • Question: Where do you get the OVEN? • Answer: Heavy Ion Collisions! Thomas K Hemmick

9. RHIC • RHIC = Relativistic Heavy Ion Collider • Located at Brookhaven National Laboratory Thomas K Hemmick

10. RHIC Specifications • 3.83 km circumference • Two independent rings • 120 bunches/ring • 106 ns bunch crossing time • Can collide ~any nuclear species on ~any other species • Top Center-of-Mass Energy: • 500 GeV for p-p • 200 GeV/nucleon for Au-Au • Luminosity • Au-Au: 2 x 1026 cm-2 s-1 • p-p : 2 x 1032 cm-2 s-1(polarized) 6 5 1’ 3 4 1 2

11. STAR RHIC’s Experiments Thomas K Hemmick

12. RHIC in Fancy Language • Explore non-perturbative “vacuum” by melting it • Temperature scale • Particle production • Our ‘perturbative’ region is filled with • gluons • quark-antiquark pairs • A Quark-Gluon Plasma (QGP) • Experimental method: Energetic collisions of heavy nuclei • Experimental measurements:Use probes that are • Auto-generated • Sensitive to all time/length scales Thomas K Hemmick

13. RHIC in Simple Language • Suppose… • You lived in a frozen world where water existed only as ice • and ice comes in only quantized sizes ~ ice cubes • and theoretical friends tell you there should be a liquid phase • and your only way to heat the ice is by colliding two ice cubes • So you form a “bunch” containing a billion ice cubes • which you collide with another such bunch • 10 million times per second • which produces about 1000 IceCube-IceCube collisions per second • which you observe from the vicinity of Mars • Change the length scale by a factor of ~1013 • You’re doing physics at RHIC! Thomas K Hemmick

14. Nature’s providence How can we hope to study such a complex system? g, e+e-, m+m- p, K, h, r, w, p, n, f, L, D, X, W, D, d, J/Y,… PARTICLES! Thomas K Hemmick

15. Deducing Temperature from Particles • Maxwell knew the answer! • Temperature is proportional to mean Kinetic Energy • Particles have an average velocity (or momentum) related to the temperature. • Particles have a known distribution of velocities (momenta) centered around this average. • All the RHIC experiments strive to measure the momentum distributions of particles leaving the collision. • Magnetic spectrometers measure momentum of charged particles. • A variety of methods identify the particle species once the momentum is known: • Time-of-Flight • dE/dx Thomas K Hemmick

16. a s STAR Magnetic Spectrometers • Cool Experiment: • Hold a magnet near the screen of a B&W TV. • The image distorts because the magnet bends the electrons before they hit the screen. • Why? : 1 meter of 1 Tesla field deflects p = 1 GeV/c by ~17O Thomas K Hemmick

17. Particle Identification by TOF e p • The most direct way • Measure b by distance/time • Typically done via scintillators read-out with photomultiplier tubes • Time resolutions ~ 100 ps K p • Exercise: Show • Performance: • dt ~ 100 ps on 5 m flight path • P/K separation to ~ 2 GeV/c • K/p separation to at least 4 GeV/c Thomas K Hemmick

18. b x=bt Ze p K p STAR e Particle Identification by dE/dx • Elementary calculation of energy loss: Charged particles traversing material give impulse to atomic electrons: • dE/dx: • The 1/ b2 survives integration over impact parameters • Measure average energy loss to find b • Used in all four experiments Thomas K Hemmick

19. Measuring Sizes • Borrow a technique from Astronomy: • Two-Particle Intensity Interferometry • Hanbury-Brown Twiss or “HBT” • Bosons (integer spin particles like photons, pions, Kaons, …) like each other: • Enhanced probability of “close-by” emission

20. Measuring Shapes • Momentum difference can be measured in all three directions: • This yields 3 sizes: • “Long” (along beam) • “Out” (toward detector) • “Side” (left over dimension) • Conventional wisdom: • The “Long” axis includes the memory of the incoming nuclei. • The “Out” axis appears longer than the “Side” axis thanks to the emission time: Thomas K Hemmick

21. Run-2000 • First collisions:15-Jun-00 • Last collisions: 04-Sep-00 • RHIC achieved its First Year Goal (10% of design Luminosity). • Most of the data were recorded in the last few weeks of the run. • The first public presentation of RHIC results took place at the Quark Matter 2001 conference. • January 15-20 • Held at Stony Brook University • Recorded ~5M events Thomas K Hemmick

22. How Do You Detect Plasma? • During a plenary RHI talk at APS about 10 years ago, I wound up seated among “real” plasma physicists who made numerous comments: • “These guys are stupid…” • Always a possibility. • “…why don’t they just shoot a laser through it and then they’d know if its plasma for sure!” • Visible light laser…bad idea. • Calibrated probe through QGP…good idea… • …but not new. (Wang, Gyulassy, others…) Thomas K Hemmick

23. The “Calibrated” Plasma Probe • Many Many results (concentrate on one). • Hard scattering processes (JETS!) : • Occur at short time scales. • Are “calculable” (even by experimentalists) in simple models (e.g. Pythia) with appropriate fudging: • Intrinsic kT • K scaling factor. • Find themselves enveloped by the medium • Are “visible” at high pT despite the medium • Promise to be our laser shining (or not) through the dense medium created at RHIC. • We can measure the ratio of observed to expected particle yield at large momentum and it should drop below 1.0. • Scaled proton-proton collisions provide reference. Thomas K Hemmick

24. “Peripheral” Particle Physics Nuclear Physics “Thermal” Production Hard Scattering “Central” Particle Spectra Evolution Thomas K Hemmick

25. RAA is below 1 for both charged hadrons and neutral pions. The neutral pions fall below the charged hadrons since they do not suffer proton contamination Raa • We define the nuclear modification factor as: • By definition, processes that scale with Nbinary will produce RAA=1. • RAA is what we get divided by what we expect. • RAA should be ~1.0 Thomas K Hemmick

26. Away-side Jets Missing! • STAR Experiment reconstructs azimuthal correlations. • Peak Around 0 are particles from “same side jet”. • Peak at +/- p is the away-side jet. • In central collisions the away-side jet disappears!!! • Medium is black to jets. Thomas K Hemmick

27. Quantifying the away-side. • Near-side jet/pp data ~1.0. • Away-side jet/pp falls to ~0.2 in central collisions. • Simple jet-quenching confirmed? • Not so fast… Thomas K Hemmick

28. “Jet” Particle Composition • Composition of jets violates normal pQCD! • How could jet fragmentation be affected? • Puzzles Puzzles Puzzles… Thomas K Hemmick

29. Other Bizarre Results: • Azimuthal asymmetries beyond the “black almond” scenario. • The HBT interferometric technique for determining the lifetime of the particle source. • The theoretical community simply can’t explain the data. • PS—This is the good news  Thomas K Hemmick

30. Another Surprise! • Rout<Rside!!!!! • Normal theory cannot account for this • Imaginary times of emission!! Thomas K Hemmick

31. Shells of ordinary matter Possible Explanation?? • Stony Brook theory student Derek Teaney(advisor E. Shuryak) calculated an exploding ball of QGP matter. • The exploding ball drives an external shell of ordinary matter to high velocities • Rout is the shell thickness • Rside is the ball size Plasma Thomas K Hemmick

32. Is it Soup Yet? • RHIC physics in some reminds me of the explorations of Christopher Columbus: • He had a strong feeling that the earth was round without having detailed calculations to back him up. • He traveled in exactly the wrong direction, as compared to conventional wisdom. • He discovered the new world… • But he thought it was India! • Our status: • We see jet quenching for the first time. • We see results which defy all predictions • Hard proton production exceeds pion production • Imaginary emission time • We could be in India (QGP), the New World, or just a place in Europe where the customs are VERY strange. Thomas K Hemmick

33. Summary • RHIC is more exciting than we dared hope: • We see jet quenching for the first time. • We see results which defy all predictions • Hard proton production exceeds pion production • Imaginary emission time • Even the hard physics “reference” fails in the face of our new matter. • 2002 run: • d-Au collisions to finalize nuclear effects that could fake jet suppression. • p-p results for nucleon spin measurements. • 2002-2003 run: • Au-Au … for high statistics. • Electromagnetic Probes!! Thomas K Hemmick

34. Summary • Extreme Energy Density is a new frontier for explorations of the state of the universe in the earliest times. • The RHIC machine has just come on line: • The machine works • The experiments work • The data from signatures of QGP as well as outright surprises… It’s not your Father’s Nuclear Matter anymore! • The real look into the system will come in the next run (May 2001): • Electrons, Photons, Muons • We dream of India as our glorious destination • But maybe…. We’ll find the new world instead. Thomas K Hemmick

35. E/p matching for p>0.5 GeV/c tracks All tracks Electron enriched sample (using RICH) Electron Identification • Problem: They’re rare • Solution: Multiple methods • Cerenkov • E(Calorimeter)/p(tracking) matching Thomas K Hemmick

36. D0 K-p+ Dalitz and conversions e- D0 K- e+ ne D0 K-m+ nm charm e- beauty e- B0 D-p+ Drell-Yan e- B0 D- e+ ne B0 D-m+ nm D0D0m+m- K+ K-nmnm D0D0 e+e- K+ K-nene D0D0m+e- K+ K-nenm Study by Mickey Chiu, J. Nagle Why electrons? • One reason: sensitivity to heavy flavor production • Other reasons: vector mesons, virtual photons  e+e- Thomas K Hemmick

37. PHENIX p0 reconstruction pT > 2 GeV/c Asymmetry < 0.8 p0 Reconstruction • A good example of a “combinatoric” background • Reconstruction is not done particle-by-particle • Recall: p0 ggand there are ~200 p0 ‘sper unit rapidity • So:p01  g1A +g1Bp02  g2A +g2Bp03  g3A +g3Bp0N  gNA +gNB • .Unfortunately, nature doesn’t use subscripts on photons • N correct combinations: (g1A g1B), (g2A g2B), … (gNA gNB), • N(N-1)/2 – N incorrect combinations (g1A g2A), (g1A g2B), … • Incorrect combinations ~ N2 (!) • Solution: Restrict N by pT cuts use high granularity, high resolution detector Thomas K Hemmick

38. BRAHMS An experiment with an emphasis: • Quality PID spectra over a broad range of rapidity and pT • Special emphasis: • Where do the baryons go? • How is directed energy transferred to the reaction products? • Two magnetic dipole spectrometers in “classic” fixed-target configuration Thomas K Hemmick

39. PHOBOS An experiment with a philosophy: • Global phenomena • large spatial sizes • small momenta • Minimize the number of technologies: • All Si-strip tracking • Si multiplicity detection • PMT-based TOF • Unbiased global look at very large number of collisions (~109) Thomas K Hemmick

40. PHOBOS Details • Si tracking elements • 15 planes/arm • Front: “Pixels” (1mm x 1mm) • Rear: “Strips”(0.67mm x 19mm) • 56K channels/arm • Si multiplicity detector • 22K channels • |h| < 5.3 Thomas K Hemmick

41. Hits in SPEC Tracks in SPEC Hits in VTX 130 AGeV PHOBOS Results First results on dNch/dh • for central events • At ECM energies of • 56 Gev • 130 GeV (per nucleon pair) To appear in PRL (hep-ex/0007036) X.N.Wang et al. Thomas K Hemmick

42. Time Projection Chamber Magnet Coils Silicon Vertex Tracker TPC Endcap & MWPC FTPCs ZCal ZCal Endcap Calorimeter Vertex Position Detectors Barrel EM Calorimeter Central Trigger Barrel or TOF RICH STAR • An experiment with a challenge: • Track ~ 2000 charged particles in |h| < 1 Thomas K Hemmick

43. STAR Challenge Thomas K Hemmick

44. STAR Event Data Taken June 25, 2000. Pictures from Level 3 online display. Thomas K Hemmick

45. STAR Reality

46. PHENIX GlobalMVD/BB/ZDC • An experiment with something for everybody • A complex apparatus to measure • Hadrons • Muons • Electrons • Photons Executive summary: • High resolution • High granularity Muon Arms Coverage (N&S) -1.2< |y| <2.3 -p < f < p DM(J/y )=105MeV DM(g) =180MeV 3 station CSC 5 layer MuID (10X0) p(m)>3GeV/c WestArm East Arm South muon Arm North muon Arm Central Arms Coverage (E&W) -0.35< y < 0.35 30o <|f |< 120o DM(J/y )= 20MeV DM(g) =160MeV Thomas K Hemmick

47. PHENIX Design

48. PHENIX Reality January, 1999 Thomas K Hemmick

49. PHENIX Results (See nucl-ex/0012008) • Multiplicity grows significantly faster than N-participants • Growth consistent with a term that goes as N-collisions (as expected from hard scattering) Thomas K Hemmick

50. Summary • The RHIC heavy ion community has • Constructed a set of experiments designed for the first dedicated heavy ion collider • Met great challenges in • Segmentation • Dynamic range • Data volumes • Data analysis • Has begun operations with those same detectors • Quark Matter 2001 will • See the first results of many new analyses • See the promise and vitality of the entire RHIC program Thomas K Hemmick