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2008 Nobel Prize in physics… October 7, 2008

Posted by apetrov in Particle Physics, Physics, Science.

… was given today to Yoichiro Nambu of the University of Chicago “for the discovery of the mechanism of spontaneous broken symmetry in subatomic physics” and to Makoto Kobayashi and Toshihide Maskawa “for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature.” A Nobel Prize in particle physics.

Nambu is well-known for his work on the origins of spontaneous breaking of symmetries in quantum field theories (in particular related to strong interactions, where he addressed spontaneous breaking of chiral symmetry – which nowdays is a base of the standard language for description of low-energy pion interactions) and has many things associated with his name (Nambu-Goldstone bosons, Nambu-Jona-Lasinio model, Han-Nambu quarks (which happen to have incorrect color charge assignment), etc.).

Kobayashi and Maskawa are given the prize essentially for the CKM (Cabibbo-Kobayashi-Maskawa) matrix. CKM matrix is a generalization of the Cabibbo’s idea that quarks actually mix – he used it to explain strange results in the physics of weak decays of strange quark, where properties of weak transitions of strange quark from non-leptonic hyperon decay rates differ from the ones in semileptonic kaon decays. Since, in particle phsyics, up-, down-, and strange-quarks belong to the first two generations of quarks, this mixing is described by a two-by-two matrix. Anyhow, Kobayashi and Maskawa generalized this idea to the case of three generations (3×3 matrix). It so happens that this “generalization” predicts a new phenomenon in weak decays of elementary particles: CP-violation orginating from the CKM matrix! In other words, it describes a difference between matter and anti-matter interactions in the Standard Model, which is needed for generating baryon asymmetry of the Universe (Ok, this now sounds like my “Introduction to particle physics” lecture for beginning graduate students)… Unfortunately, there is “not enough CP-violation” in the CKM matrix to claim explanation of the baryon asymmetry of the Universe from the Standard Model, BUT: this source of CP-violation was experimentally confirmed! And now studies of the CKM matrix serve as a base for indirect studies of New Physics in low-energy transitions — which, if discovered, will be used as additional information needed to classify possible New Physics possibly observed at the LHC, once they fix it… And that’s why Nobel Prize was given to Kobayashi and Maskawa.

Still, I can’t believe they didn’t give it to Cabibbo as well..

P.S. There is an intersting local story that was told to me once I got to WSU. Nambu is also considered one of the fathers of string theory (look for Nambu-Goto action). So the story is that in the 60s there was a quark-model conference at WSU hosted by Suraj Gupta, during which Nambu came up with his idea to describe hadrons in terms of strings. How about that?



1. Nobel for symmetry breaking « Antimatter - October 7, 2008

[…] a more technical discussion of the issues above, see the Symmetry Factor blog. An important point made is that the third musketeer of the Cabibbo-Kobayashi-Maskawa matrix […]

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