What have we learned from RHIC? Mark D. Baker Chemistry Department

1. What have we learned from RHIC?Mark D. BakerChemistry 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/ Mark D. Baker

2. Some of the people Mark D. Baker

3. 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 Mark D. Baker

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

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

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

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

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

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

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

11. How do we get to 2 trillion oK? 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 Mark D. Baker

12. 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 Mark D. Baker

13. Where? Mark D. Baker

14. Inside the tunnel Mark D. Baker

15. STAR Mark D. Baker

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

17. First Collisions Mark D. Baker

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

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

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

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

22. Elliptic Flow: A collective effect Beam’s eye view of a non-central collision: Asymmetric particle distribution: f Particles prefer to be “in-plane” dN/d(f -YR ) = N0 (1 + 2V1cos (f-YR) + 2V2cos (2(f-YR)) + ... ) Elliptic flow Mark D. Baker

23. Elliptic Flow Expectations Particle asymmetry midrapidity : |h| < 1.0 V2 Hydrodynamic model Hydrodynamic “Flow” Preliminary No collective motion Normalized Multiplicity Mark D. Baker

24. Elliptic Flow PRL 86 (2001) 402 Particle asymmetry midrapidity : |h| < 1.0 V2 Hydrodynamic model Preliminary Normalized Multiplicity Mark D. Baker

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

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

27. 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 Mark D. Baker

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

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

30. RHIC shows rapid expansion & a high temperature Effective Temperature (GeV) STAR Preliminary CERN NA49 1.7 1012 oK Mark D. Baker

31. 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” (mB) Mark D. Baker

32. Temperature from particle ratios STAR Preliminary T = (2.2+0.2) 1012 oK - 4 6 3 2 1,5,7 Mark D. Baker

33. Temperature at Freezeout • Chemical: T = (2.2+0.2) 1012 oK • Kinetic: T = (1.7+0.4) 1012 oK • We did reach ~ 2 trillion K! - - Mark D. Baker

34. 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. Mark D. Baker

35. 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 Mark D. Baker

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

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

38. 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. Mark D. Baker

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