1. The nucleus at a trillion degrees David Morrison Brookhaven National Laboratory

2. Where can we find it?  early universe … tough. very tough.  high energy nuclear collisions. creates only very small quantities of stuff creates only very small quantities of stuff the created stuff is very short-lived the created stuff is very short-lived requires a big accelerator requires a big accelerator requires complex detectors requires complex detectors tough … but doable tough … but doable

3. quarkshadrons mesonsbaryons pions, kaons,... protons, neutrons,... nucleons protonsneutrons partons quarksgluons Some terminology

4. High energy nuclear collision contracted by effects of special relativity impact parameter

6. Aftermath of a collision As seen by STAR experiment at RHIC End-on view of high energy gold-gold collision more than 5000 particles you only see the charged particles here (there are also lots of neutral particles) your eye doesn’t really see particle momenta, correlations, distributions

7. Corona: 10 6 K Center: 10 7 K Surface: 6000 K Solar and Heliospheric Observatory (SOHO) satellite

8. Planck distribution describes intensity as a function of the wavelength of the emitted radiation “Blackbody” radiation is the spectrum of radiation emitted by an object at temperature T  E  p

9. intensity  transverse momentum  Systematic Errors not shown Phobos Preliminary Determining temperature From transverse momentum distribution deduce temperature of about 120 MeV

10. Energy density  A typical approach use calorimeters to measure energy emitted from collision use calorimeters to measure energy emitted from collision estimate the volume of the collision estimate the volume of the collision  obtain energy densities ranging up to several GeV/fm 3

11. Energy density in highest energy head-on Au+Au collisions – more than 5 GeV/fm 3 Calorimeters in PHENIX

12. 5 GeV/fm 3. Is that a lot? Last year, the U.S. used about 100 quadrillion BTUs of energy: At 5 GeV/fm 3, this would fit in a volume of: Or, in other words, in a box of the following dimensions:

14. Chemical equilibrium 2H 2 O + energy  2H 2 + O 2 time  concentration of O 2  equilibrium concentration will depend on intensive quantities: T, p t1t1 t2t2

15. Not just your usual quarks Not exactly the way I think of them … Ordinary matter made of up and down quarks

16. Chemical equilibrium With enough time, forward and reverse reactions will drive system to chemical equilibrium. Abundances will only depend on temperature and chemical potential.

17. One way to dig even deeper hadron  possible for “knock- on” collisions of partons  seen in high-energy physics experiments since mid-1970’s  a real particle physics phenomenon that can be used to probe the trillion degree material we create

18. Force between two quarks Compare to gravitational force at Earth’s surface Quarks exert 16 metric tons of force on each other! quark gluons

19. A “jet” of particles  as connection between quarks breaks up, most of the motion stays close to direction of the original quarks  the fragmented bits appear as “normal” subatomic particles pions, kaons, … pions, kaons, … kaon pion

22. An algorithm  a way to locate the running of the bulls in Pamplona, Spain: 1. start by finding one high- momentum bull 2. look others moving in roughly the same direction 3. if the bull density is high, you might reconsider the place you’ve chosen to stand The next step is simple: just replace “bull” by “particle”

23. Case study: opacity of fog  “is this thing on?”  if you detect one beam, at least know the source is on  intensity of the “other” beam tells you a lot

24. Pedestal&flow subtracted angle away from initial high momentum particle  intensity  same directionopposite direction

25. The matter we make …  is fantastically hot  has incredible energy density  only exists for an instant, but shows many signs of equilibrium  some properties are more straightforward to explain in language of partons  very, very “sticky” – partons lose lots of energy trying to get through it  being studied in dozens of ways – lots of new results anticipated at Quark Matter ‘04!

26. Heavy-Ion Physics (materia in extremis)