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Feynman's partons


Bjorken's idea
Murray Gell-Mann Scientist
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He generalized the idea of abstracting current algebra to a different regime, but this was a regime where in the model field theory the current algebra wouldn't actually hold exactly, only for free particles. So basically what he was doing was suggesting that in these limits that he discussed, that the quarks would behave almost like free particles, and that was very interesting because it led to results in agreement with observation. The Stanford and MIT group at SLAC: Dick Taylor, Jerry Friedman, Henry Kendall and many others were doing experiments on deep inelastic scattering; electrons hitting the proton and then going off with a certain momentum transfer, a certain invariant momentum transfer. And what they looked at was what happened… was the probability of that—irrespective of what kind of junk was made on the hadronic side—summing over all the different products that were made on the… out of the proton. They did this in the deep inelastic limit and they had no idea that they were going to be testing the quark idea; they were just interested in what happened in this limit, they thought it would throw some light on physical reality. I don't think they had any notion of testing the quark hypothesis. In fact I think they thought… many people thought that the cross-section would go down, I mean it would be like a standard form factor. But in the long run they found that… in the long run what they accomplished was to confirm the quark hypothesis. What I tell audiences in popular talks is that what they did essentially was to take an electron micrograph of the proton and find that it was made of three nearly punctiform objects with the properties of quarks, including the squares of the charges: four-ninths, one-ninth and one-ninth. Well, Bjorken's idea helped them very much to accomplish this interpretation. But it was somewhat unclear theoretically why one should be able to abstract the result that wasn't even true in the model field theory that we were throwing away, but was true only in the limit of very weak coupling. What was it that made the coupling weak in this deep inelastic limit?

New York-born physicist Murray Gell-Mann (1929-2019) was known for his creation of the eightfold way, an ordering system for subatomic particles, comparable to the periodic table. His discovery of the omega-minus particle filled a gap in the system, brought the theory wide acceptance and led to Gell-Mann's winning the Nobel Prize in Physics in 1969.

Listeners: Geoffrey West

Geoffrey West is a Staff Member, Fellow, and Program Manager for High Energy Physics at Los Alamos National Laboratory. He is also a member of The Santa Fe Institute. He is a native of England and was educated at Cambridge University (B.A. 1961). He received his Ph.D. from Stanford University in 1966 followed by post-doctoral appointments at Cornell and Harvard Universities. He returned to Stanford as a faculty member in 1970. He left to build and lead the Theoretical High Energy Physics Group at Los Alamos. He has numerous scientific publications including the editing of three books. His primary interest has been in fundamental questions in Physics, especially those concerning the elementary particles and their interactions. His long-term fascination in general scaling phenomena grew out of his work on scaling in quantum chromodynamics and the unification of all forces of nature. In 1996 this evolved into the highly productive collaboration with James Brown and Brian Enquist on the origin of allometric scaling laws in biology and the development of realistic quantitative models that analyse the influence of size on the structural and functional design of organisms.

Tags: Stanford, MIT, SLAC, James Bjorken, Dick Taylor, Jerry Friedman, Henry Kendall

Duration: 2 minutes, 53 seconds

Date story recorded: October 1997

Date story went live: 29 September 2010