1. Mark D. Baker What have we learned from RHIC? Mark D. Baker Chemistry Department Thanks to: W. Busza, Axel Drees, J. Katzy, B. Lugo, P. Steinberg, N. Xu, F. Wolfs BSA Lecture Committee Particle Data Group http://ParticleAdventure.org/

2. Mark D. Baker Some of the people

3. Mark D. Baker Where they come from BNL –Chemistry, Collider-Accelerator, Physics >1000 people from around the world –Brazil, Canada, China, Croatia, Denmark, France, Germany, India, Israel, Japan, Korea, Norway, Poland, Russia, Sweden, Taiwan, UK, US

4. Mark D. Baker What is the universe made of? & What holds it together?

5. Mark D. Baker What is the universe made of? Placeholder

6. Mark D. Baker What holds it together?: The Fundamental Forces

7. Mark D. Baker Let’s smash some atoms! + - - u u u u u u d ud ud ud ud proton pion (  ) u u d

8. Mark D. Baker If you can’t smash it, heat it! Temperature Plasma + -- - - + Pressure

9. Mark D. Baker Sideways slide - How much heat? Placeholder

10. Mark D. Baker Heat is also a window back in time

11. Mark D. Baker How do we get to 2 trillion o K? Collide Gold nuclei at 99.99% of the speed of light But: Will these fast violent collisions teach us anything? 10 -23 seconds, 10 -38 liters

12. Mark D. Baker The plan of attack Collide gold nuclei at high energy –Collider, detectors, computers Understand the collision dynamics –Collective motion, equilibrium –Temperature, density Learn about the strong interaction –Quark-Gluon Plasma –Confinement

13. Mark D. Baker Where?

14. Mark D. Baker Inside the tunnel

15. Mark D. Baker STAR

16. RHIC Computing Facility The detectors can take 7 Gigabytes of data / minute!

17. Mark D. Baker First Collisions

18. Mark D. Baker Timeline Collisions Delivered Star & Phobos Brahms & Phenix |-----June------|-----July------|----August----|--September--|---October---|---November--| 2000  s NN = 130 GeV Au-Au |-December--|--January---|--February--|----March----|-----April-----| (PHOBOS) (STAR) (PHENIX) 1st Collisions Papers (PHENIX) (BRAHMS)(PHOBOS) (STAR) Papers

19. Mark D. Baker Looking for collective effects... Is Gold+Gold > 197 * Proton+Proton?

20. Mark D. Baker AuAu @ RHIC is something new! PHOBOS CERN/SPS Energy/nucleon (GeV) Produced Particles/ Participating Nucleon Pair PHENIX BRAHMS prelim. PRL 85 (2000) 3100

21. Mark D. Baker How many produced particles? Measured # in a head-on collision: 4100±410 (Simulation) PHOBOS Preliminary

22. Mark D. Baker Elliptic Flow: A collective effect dN/d(  R ) = N 0 (1 + 2V 1 cos (  R ) + 2V 2 cos (2(  R )) +... ) Elliptic flow Beam’s eye view of a non-central collision: Asymmetric particle distribution: Particles prefer to be “in-plane” 

23. Mark D. Baker Elliptic Flow Expectations Hydrodynamic model V2V2 Normalized Multiplicity midrapidity : |  | < 1.0 Preliminary Particle asymmetry No collective motion Hydrodynamic “Flow”

24. Mark D. Baker Elliptic Flow Hydrodynamic model V2V2 Normalized Multiplicity midrapidity : |  | < 1.0 Preliminary PRL 86 (2001) 402 Particle asymmetry

25. Mark D. Baker Collective motion largest at RHIC STAR, PRL 86 (2001) 402

26. Mark D. Baker It even makes sense in detail Huovinen, Kolb, Heinz Particle asymmetry

27. Mark D. Baker Plan of attack - where are we? Collide gold nuclei at high energy –Collider, detectors, computers Understand the collision dynamics –Collective motion, equilibrium –Temperature, density Learn about the strong interaction –Quark-Gluon Plasma –Confinement

28. Mark D. Baker We see the conditions at freezeout (a lower limit to the maximum Temperature) FreezeoutHottest period Expansion cooling

29. Mark D. Baker Separating Temperature & Expansion Compare produced particles with different masses! Effective Temperature mass

30. Mark D. Baker 1.7 10 12 o K RHIC shows rapid expansion & a high temperature Effective Temperature (GeV) CERN NA49 STAR Preliminary

31. Mark D. Baker Another thermometer In an equilibrium system, two parameters are sufficient to predict the “chemical” mix: (# pions) / (# protons) (# kaons) / (# pions) (# anti-protons)/(# protons) et cetera. Temperature (T) and “net amount of matter” (  B )

32. Mark D. Baker Temperature from particle ratios T = (2.2+0.2) 10 12 o K - STAR Preliminary 2 3 6 4 1,5,7

33. Mark D. Baker Temperature at Freezeout Chemical: T = (2.2+0.2) 10 12 o K Kinetic: T = (1.7+0.4) 10 12 o K We did reach ~ 2 trillion K! - -

34. Mark D. Baker The yields are compared to predictions by Hijing. The SPS data values from NA44, NA49 are plotted as reference. The  ~3 measurement converted to y using the accepted mean pt.

35. Mark D. Baker What happens before freeze-out? Energetic particles come from quark or gluon “jets”. They interact with the dense medium, but can’t thermalize. Jet energy loss (“quenching”) is predicted. Jet quenching measures the density early in the collision. pion

36. Mark D. Baker Jet quenching at RHIC? Neutral pions Central collisions No quenching Number Transverse Momentum (GeV/c) Neutral pions Peripheral collisions Quenching Transverse Momentum (GeV/c) Preliminary

37. Mark D. Baker More on jet quenching Details need to be understood before conclusions can be drawn.

38. Mark D. Baker Summary We’ve learned a lot about the system –We have reached ~2 trillion degrees K –The system is expanding rapidly. –It was probably even hotter and denser Possible first evidence of jet quenching! –Should lead to a measure of the density No conclusions yet about the strong force.

39. Mark D. Baker Outlook More analysis More data (x100 next run) –Allows new early time probes More variety of data –Energy and species scan Detector Upgrades It’s going to get even better! Stay tuned for news about the strong force!