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The 2004 Nobel Prize in Physics: 

The 2004 Nobel Prize in Physics Craig Tyler, Physics & Engineering

the physics prize: 

the physics prize Usually for experiments, rather than theory Often shared, rather than individual

meet the new laureates: 

meet the new laureates “For the discovery of asymptotic freedom in the theory of the strong interaction” (1973, when Politzer and Wilczek were grad students). David J. Gross, UCSB; H. David Politzer, Caltech; Frank Wilczek, MIT (They’ll share equally a prize of $1.35 million)

the particle physics world: 

the particle physics world Gravity Weak nuclear force Electromagnetic force Strong nuclear force Quarks (which live inside atomic nuclei) Leptons (electrons and neutrinos) Force carriers (gravitons, weakons, photons, and gluons)


quarks Protons contain uud Neutrons contain udd But there are 6 “flavors” In 3 “generations” Each of which can have 3 “colors,” according to QCD, quantum chromodynamics (We’ve made these in accelerator experiments) Quarks interact mainly by the strong nuclear force, by the exchange of gluons

the discovery: 

the discovery The new laureates discovered the nature of the strong force, “asymptotic freedom,” which taught us all this: QCD and colors, like red or anti-green. Stable quark arrangements are “white.” Stable quark arrangements are confined. Gluons, which have colors too, and therefore interact with each other.

asymptotic freedom: 

asymptotic freedom The strong force is unlike the others: if gluons interact with each other, then at close range, when there are lots of gluons zipping around, they’ll get tied up with each other and forget the quarks – so the quark force dies! Thus, the strength of the strong force is weak at close range, and strong at “long” range! Freedom: at close range inside atomic nuclei, the quarks bounce around freely (contrast electrons in atoms)

some evidence: 

some evidence 2-jet events… Collision making quarks White confined states needing additional quarks Quark-Gluon Plasma, not seen in this universe (as far as we know) since the big bang beginning!

more evidence: 

more evidence … and 3-jet events Not to mention “strange stars”

what we still don’t know : 

what we still don’t know Why are there 3 generations? 3 colors? 6 flavors? Why not some other number? Where’s all the anti-matter? You never see it around. Where do different masses (of quarks, say) come from? Is there supersymmetry? String theory? Extra dimensions? Dark matter? A “GUT”? A “TOE”? … So there are plenty of Nobel Prizes left for you, if you want to major in physics.

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