The nucleus at a trillion degrees

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 • the created stuff is very short-lived • requires a big accelerator • requires complex detectors • tough … but doable

3. partons hadrons quarks quarks gluons mesons baryons nucleons pions, kaons, ... protons, neutrons, ... protons neutrons Some terminology

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

6. Aftermath of a collision 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 As seen by STAR experiment at RHIC

7. Corona: 106 K Center: 107 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  Phobos Preliminary Systematic Errors not shown transverse momentum  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 • estimate the volume of the collision • obtain energy densities ranging up to several GeV/fm3

11. Calorimeters in PHENIX Energy density in highest energy head-on Au+Au collisions – more than 5 GeV/fm3

12. 5 GeV/fm3. Is that a lot? Last year, the U.S. used about 100 quadrillion BTUs of energy: At 5 GeV/fm3, this would fit in a volume of: Or, in other words, in a box of the following dimensions:

14. Chemical equilibrium 2H2O + energy  2H2 + O2 concentration of O2 time t1 t2 equilibrium concentration will depend on intensive quantities: T, p

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

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 • 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 hadron hadron

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

19. A “jet” of particles pion • 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, … pion pion kaon

22. An algorithm • a way to locate the running of the bulls in Pamplona, Spain: • start by finding one high-momentum bull • look others moving in roughly the same direction • 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. “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 Case study: opacity of fog

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

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)