The Little Big Bang: Relativistic Nuclear Collisions and the Physics at 10 12 K

1. The Little Big Bang: Relativistic Nuclear Collisions and the Physics at 1012 K Nathan Grau Columbia University, Nevis Laboratories Francis Marion University

2. Outline • Top-down introduction to high energy physics and the Quark-Gluon Plasma • The Quark-Gluon Plasma now • What we know now from the Relativistic Heavy Ion Collider (RHIC) • The Quark-Gluon Plasma in the future • What we are learning and will learn from the Large Hadron Collider, string theory, and trapping supercold atoms Francis Marion University

3. Introduction and Background of High Energy Physics WARNING! The units you are about to see and hear are “natural” c = hbar = kB = 1 Energy in GeV, momentum GeV/c (p~mc), mass in GeV/c2 (E=mc2) Some important numbers to set a scale: Proton mass = 1 GeV/c2 170 MeV = 1012 K (E=kBT) Francis Marion University

4. The Standard Model Lagrangian • This is the culmination of 400+ years of physics research • All current physics data is explained • Disclaimer: Gravity Not Included • Still not small enough to fit on a T-shirt • Good party trick: Ask where the sign error is (there really is one!) Francis Marion University

5. The Standard Model Condensed • The particles (fields) • 12 particles • 4 force carriers • Their interactions are the fundamental forces of nature… Francis Marion University

6. Computer Chip Fundamental Forces: Electroweak • 1/2 Electroweak Force = Electricity and Magnetism • Everything from transistors in computers to wind is governed by this force • Actually a single force: Electromagnetic force • Interaction of two charged entities • Theory: Quantum Electrodynamics (QED) Hurricane Katrina Francis Marion University

7. Fundamental Forces: Electroweak p p p p • 1/2 Electroweak Force = Weak Force • interaction of two “weakly” charged particles • It is why the sun shines. • In the first part of the chain the proton turns into a neutron. light He Francis Marion University

8. Quarks combine to form other particles • Baryons (qqq): protons, neutrons, etc. • Mesons( ): pions, kaons, etc. • Held together by gluons • Quark charge is “color” of 3 types: red, green, blue • Contrast that with 2 electric charges: +,- • Hadrons are color neutral = white g proton neutron g g g g g Fundamental Forces: Strong Force Francis Marion University

9. g proton neutron g g g g g Fundamental Forces: Strong Force • Quarks combine to form other particles • Baryons (qqq): protons, neutrons, etc. • Mesons( ): pions, kaons, etc. • Held together by gluons • Quark charge is “color” of 3 types: red, green, blue • Contrast that with 2 electric charges: +,- • Hadrons are color neutral = white • Theory: Quantum Chromodynamics (QCD) Francis Marion University

10. Quarks combine to form other particles • Baryons (qqq): protons, neutrons, etc. • Mesons( ): pions, kaons, etc. • Held together by gluons • Quark charge is “color” of 3 types: red, green, blue • Contrast that with 2 electric charges: +,- • Hadrons are color neutral = white • Theory: Quantum Chromodynamics (QCD) g proton neutron g g g g g Fundamental Forces: Strong Force Ca. 1970 view of the proton and the neutron. Only real improvement is that the proton bubbles with lots of gluons and pairs Francis Marion University

11. d g d g u g u u g u Proton Structure • Proton at two instances in time • The interior bubbles with pairs and gluons Francis Marion University

12. Proton Structure • Probability of finding a gluon or quark of a given flavor with momentum fraction x = pq/pp • u, d = valence near x~10-1 • s,c,b,g = sea Francis Marion University

13. Fundamental Forces: Strong Force • Strong force also binds nuclei • Clearly needed another nuclear force since an electrically neutral neutron could not bind with a positive proton via electromagnetic force • In fact, individual proton and neutron definitions are blurred by quantum mechanics • Nucleus is a bag of quarks and gluons Francis Marion University

14. Confinement Quarks and gluons are confined - no evidence of their existence outside of (colorless) hadrons Francis Marion University

15. The Quark-Gluon Plasma: Unbinding the Bound Francis Marion University

16. The History of the Universe Francis Marion University

17. Francis Marion University

18. The Quark-Gluon Plasma • The state of the universe before it cooled to allow hadrons (protons, neutrons, etc.) to form • t < 1 s after the Big Bang • Hence part of my title • T > 1012 K • Hence the other part of my title • R < 1 fm = size of the proton • It is a different state of matter than what exists today • Can we reproduce it in a laboratory? • Allow a direct study of the strong interaction which is 1/2 of the Standard Model. Francis Marion University

19. QCD Phase Diagram • A beginning definition: A hot, dense state of weakly-interacting quarks and gluons over a distance greater than the size of the proton. Quark-Antiquark imbalance Francis Marion University

20. QCD Phase Diagram • A beginning definition: A hot, dense state of weakly-interacting quarks and gluons over a distance greater than the size of the proton. • Expected to occur at 1012K~170 MeV Quark-Antiquark imbalance Francis Marion University

21. QCD Phase Diagram • A beginning definition: A hot, dense state of weakly-interacting quarks and gluons over a distance greater than the size of the proton. • Expected to occur at 1012K~170 MeV Quark-Antiquark imbalance Heavy Ion Collision Trajectory Francis Marion University

22. The Relativistic Heavy Ion Collider (RHIC) From Space I live here RHIC At Brookhaven National Laboratory NYC Francis Marion University

23. The Collider From The Air Francis Marion University

24. RHIC Vitals and Statistics • Two independent rings 3.83 km in circumference • 120 bunches/ring • 106 ns crossing time • Maximum Energy • s½ = 500 GeV p+p • s½ = 200 GeV/N-N A+A • Design Luminosity • Au+Au 2x1026 cm-2s-1 • p+p 2x1032 cm-2s-1 ( polarized) • Capable of colliding any nuclear species on any other nuclear species • Collision energy = two mosquitoes colliding • Collision temperature: over 1 trillion degrees • Over 35,500 kg (78,100 pounds) of helium • Ring cooled to 4.6 Kelvin (-450 degrees F) • Refrigerator uses 15 MW electricity • 20 years, less than one gram of gold is used • Quark-gluon plasma lasts less than 0.00000000000000000000001 seconds Francis Marion University

25. A Relativistic Heavy Ion Collision • Two nuclei approach one another • Moving at v=0.9995c so relativistically contracted • Mostly pass through one another • Overlap region converts energy into heat and particles to form the QGP • Peripheral collision • Not fully overlapping • See “participants” and “spectators” Simulations by the Frankfurt UrQMD Group Francis Marion University

26. A Relativistic Heavy Ion Collision Animation by Jeffery Mitchell (Brookhaven National Laboratory). Simulation by the UrQMD Collaboration • Central (head-on) Au+Au Collision Francis Marion University

27. Real Heavy Ion Collisions STAR Francis Marion University

28. Measuring  M. Kaneta, N. Xu, nucl-th/0405068 (2004) • If  is the quark-antiquark imbalance then measure anti-particle/particle ratios • Compare to a statistical model of hadronization • Note the species measured:K, K*, p,  Francis Marion University

29. Measuring  M. Kaneta, N. Xu, nucl-th/0405068 (2004) • If  is the quark-antiquark imbalance then measure anti-particle/particle ratios • Compare to a statistical model of hadronization • Note the species measured:K, K*, p,  Francis Marion University

30. Measuring  M. Kaneta, N. Xu, nucl-th/0405068 (2004) • If  is the quark-antiquark imbalance then measure anti-particle/particle ratios • Compare to a statistical model of hadronization • Note the species measured:K, K*, p,  B~30 MeV Francis Marion University

31. Measuring T • Look at the photons • Just like COBE measures the CMB Francis Marion University

32. Measuring T: Photon Spectrum • Yield of photons at each momentum bin • Dashed line is fit to p+p data • Extra photons in Au+Au collisions • exp(-pT/T) with T = 221+/-23(stat.)+/-18(sys.) MeV • Other theoretical models are yield T from 300-600 MeV • Recall transition at T~170 MeV Francis Marion University

33. Central Au+Au Non-central Au+Au Measuring T: Photon Spectrum • Yield of photons at each momentum bin • Dashed line is fit to p+p data • Extra photons in Au+Au collisions • exp(-pT/T) with T = 221+/-23(stat.)+/-18(sys.) MeV • Other theoretical models are yield T from 300-600 MeV • Recall transition at T~170 MeV Francis Marion University

34. Central Au+Au Non-central Au+Au Measuring T: Photon Spectrum • Yield of photons at each momentum bin • Dashed line is fit to p+p data • Extra photons in Au+Au collisions • exp(-pT/T) with T = 221+/-23(stat.)+/-18(sys.) MeV • Other theoretical models are yield T from 300-600 MeV • Recall transition at T~170 MeV Francis Marion University

35. Intermediate Conclusion • It seems like RHIC has indeed produced the right conditions to produce a Quark-Gluon plasma. • But… • Do we know it is thermalized? Is that temperature from the photons really a temperature. • What about other thermodynamic quantities: pressure, entropy, etc.? Is there an equation of state? Francis Marion University

36. Getting at the Pressure: Elliptic Flow • Non-overlapping collisions of spherically symmetric nuclei results in a non-symetric overlap region • Differential pressure gradients if you think in terms of a fluid. • Use flow to measure Equation of State and speed of sound cs Francis Marion University

37. Azimuthal Distributions: v2 • Particles have a harmonic distribution wrt the reaction plane. • v2 related to the strength of the modulation • Dependent on the particle’s momentum and mass Francis Marion University

38. Compilation of Light Hadron v2 Data • Everything flows • Hydrodynamics fit data at low momentum • Should not work at high momentum • Can add K*, to this list as well Hydrodynamics = Fluid equations assuming An equation of state and thermalization. Francis Marion University

39. v2 Scaling (I) baryons (qqq) • With more precise data scaling of baryons (p,n) and mesons (,K) observed. Mesons ( ) Francis Marion University

40. v2 Scaling (II) • Divide by the constituent quarks and a universal v2 curve exists! • nq=3 for baryons • nq=2 for mesons • Can be used to derive a speed of sound: cs = 0.35+/-0.05 Francis Marion University

41. Heavy Quarks Flow Also! • Heavy Flavor(HF): c,b e • c,b flow as well! • Like boulders flowing in a small stream Several models of heavy flavor diffusion through the medium Francis Marion University

42. Strongly Interacting Plasma • Hydrodynamic models work • Only works with QGP equation of state (not a hadron gas) • Implies local thermodynamic equilibrium • Have viscosity = 0! • The medium produced is a perfect fluid • Fluid! Not a gas! • Heavy flavors are also strongly coupled to the fluid • Data used to obtain (shear)viscosity/entropy density /s • Light hadron v2 indicates /s ~ 1/4 • Heavy hadron v2 indicate /s ~ (1-2)/4 Francis Marion University

43. The Future: The Effects of RHIC and New Experiments Francis Marion University

44. Should We Have Seen This Coming? • Lattic calculations (numerically solving QCD) indicate a phase transition • But new phase doesn’t reach the Stefan-Boltzmann limit • The limit for non-interacting paticles. Francis Marion University

45. How Can We Make Headway? • If particles are strongly coupled cannot use perturbative methods to calculate • Need a new tool that can calculate strongly coupled field theories • Why not use string theory???? Francis Marion University

46. AdS/CFT Correspondence 5-D Anti-de Sitter • Maldecena’s Conjecture • 1) Calculate some quantities in a 5-D gravity • Anti-de Sitter (AdS) defines the General Relativity metric Black Hole 4-D 5th dim Francis Marion University

47. AdS/CFT J. Maldacena E. Witten et al. AdS/CFT Correspondence 5-D Anti-de Sitter • Maldecena’s Conjecture • 2) Apply a dictionary to get analogous quantity in the dual conformal field theory (CFT) • CFT: scale invariant field theory • QCD is not quite scale invariant • Shh don’t tell… Black Hole 4-D 5th dim Francis Marion University

48. AdS/CFT J. Maldacena E. Witten et al. AdS/CFT Correspondence 4-D QCD-like, strongly-coupled fluid at TQGP 5-D Anti-de Sitter Black Hole 4-D 5th dim Conformal boundary r0~1/TQGP Francis Marion University

49. What Do Strings Tell Us? • Limit of /s (looks like an uncertainty relationship) • Checked by many different geometries - seems universal! Francis Marion University

50. /s For Physical Substances • Nothing comes close to the physical bound except the QGP at TC • Recall • Light hadron v2 indicates /s~1/4 • Heavy hadron v2 indicate /s~(1-2)/4 • Most perfect fluid ever measured in a laboratory Francis Marion University