On Tuesday it was announced that Makoto Kobayashi and Toshihide Maskawa have been awarded the Nobel Prize in Physics for 2008. The award is "for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature." They share the prize with Yoichiro Nambu for his work on spontaneous symmetry breaking, a process vital to the derivation of the Higgs mechanism which gives particles mass in the standard model and which, as has been well publicised, is major part of the physics to be investigated with the LHC.
The work of Kobayashi and Maskawa concerns a slightly more obscure asymmetry in nature, so called CP violation. Essentially CP asymmetry reveals a subtle difference between the weak nuclear decays of some particles and their corresponding anti-particles and forms a cornerstone in the investigation of why the universe is made of matter and not anti-matter. It was first observed experimentally in the 1960s and at the time posed a theoretical conundrum. Kobayashi and Maskawa showed in the early 1970s that this effect could be incorporated into the standard model if there are at least 3 generations of quarks. This effectively predicted 
the yet to be discovered top and bottom quarks. Their work built on the flavour mixing formalism developed by the Italian Nicola Cabibbo and resulted in the so called CKM (Cabibbo-Kobayashi-Maskawa) matrix.
The ultimate test of the CKM matrix came this decade with the operation of the B Factories; BELLE in Japan and BaBar in the USA. These experiments produce pairs of B mesons (particle and anti-particle) and study their decays looking for the effects of CP violation predicted by Kobayashi and Maskawa. In 2001 both collaborations reported the first experimental observations of CP violation from B meson decays, completely in agreement with the CKM matrix formalism. They have since made scores of similar measurements all consistent with the model. Imperial College has been heavily involved with the BaBar experiment 
(named after the eponymous cartoon elephant who is also the experiment mascot) for the duration of it's running, which was completed earlier this year. We continue to work as part of the collaboration who are now analysing the final data set. Currently the Imperial group are looking at the effects of radiative penguin decays which can further constrain the elements of the CKM matrix.
It is the success of the CKM mechanism under intense experimental scrutiny which has made Kobayashi and Maskawa deserving winners of the 2008 Nobel Prize in physics.
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Undergraduate and Postgraduate students, Research Associates and Staff at the Imperial College London High Energy Physics Group. (everyone is invited to add comments!)
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2 comments:
Several of us in the T2K group has been out at KEK, the Japanese national particle physics laboratory, for the last week for a collaboration meeting.
Amid the endless succession of meetings, the awarding of the Nobel Prize to Kobayashi and Maskawa, and Yoichiro Nambu has been a fascinating backdrop.
Kobayashi works at KEK, and there has been a palpable buzz in the air, since we heard about the announcement during the first day of meetings.
One of the meetings I was chairing the next afternoon had to be moved away from the main hall, so that everyone could gather to listen to the new laureate speak at a celebratory event held in his honour.
Unforeseen changes in meeting rooms are common occurrences, but I don't think I have ever experienced such an agreeable reason for being kicked out of a room!
I saw an interview of Maskawa of Kyoto University, whose undergraduate relativistic quantum mechanics lectures I have a vague recollection of, where he was being asked whether he really meant it when he said he didn't really feel overjoyed upon receiving the Nobel Prize.
His answer was that as a physicist, it was the experimental results from BaBar at SLAC, and Belle at KEK about seven years ago, as Mark described in his post, that delighted him the most, by confirming that the Kobayashi-Maskawa theory was correct. The Nobel Prize is but a social phenomenon, according to him.
The blanket coverage of the three (or two) Japanese physicists receiving the Physics Nobel Prize, followed by another receiving the Chemistry Prize, has been quite astounding.
Last night there was a live TV special with Kobayashi and Maskawa, where the NHK (the BBC of Japan) tried to explain the theory that won them the Nobel Prize.
They explained what symmetry breaking was, and they explained the bold hypothesis of there being six types of quark rather than the three that had been observed at the time.
They didn't attempt to really show how the latter can explain the former, however!
Another media event was our colleague Dave Wark being dragged out of a meeting to be asked shake Kobayashi's hand in front of several TV cameras.
I am sure everyone will wish me luck as I scour the web to find a link to a clip of the video....
Nice photo, by the way!
The Babar public website has published a page which explains the B Factory contribution very well. Also linked from this page are videos of the Nobel Lectures from 8th December 2008 (Maskawa's is in Japanese)
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