Cabibbo and quark mixing


Today I have been at Accademia dei Lincei, a renowned institution located here in Rome. There was a talk by Nicola Cabibbo about quark mixing. This conference was addressed also to people not having a proper knowledge of physics, making quite exciting to listen. Cabibbo is member of the Accademia since 1973 and his groundbreaking discovery happened in 1963 (see here). There has been some fuss last year with Nobel prize awarded to Kobayashi and Maskawa but not to Cabibbo (see my post here). So, it was a chance to hear from his voice his personal recollections about all this matter.

He gave a historical overview about quark mixing and how he found himself on the right path. Then, he cited when, on 1963, he met Feynman that said him that things could not work as he got V+A in some cases rather than V-A. Indeed, confirmations arrived later.

Giorgio Salvini, an experimental physicist well-known for his contributions to high-energy physics, introduced Cabibbo recalling as, when in Frascati, after Kobayashi and Maskawa got published their paper, he hit his forehead saying “How did not I think about six quarks?”. Indeed, Cabibbo recalled when, in the sixties, he was in his office at Rome University “La Sapienza” and Shelly Glashow knocked on his door. Glashow asked to Cabibbo if his approach could be used to understand CP violation. At that time, Glashow was frequently in Rome and, some time after, he took Luciano Maiani with himself at Harvard and we all know as history went. To obtain CP violation from Cabibbo mechanism one should introduce a complex phase factor. At that time no more than four quarks were postulated. So, Cabibbo answered that was not possible as, whatever phase one introduces, this can be removed. With six quarks this is no more possible and so, he said, having not thought about six quarks, he missed in this way the possibility to uncover the full CKM matrix.

In the end of the conference, some questions were put forward and Cabibbo promised to put all the talk on paper, after Giorgio Salvini solicited him for doing this. I hope to read his paper. This is a must after such a beautiful talk.


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