# Nicola Cabibbo

Nicola Cabibbo
Born 10 April 1935
Rome, Italy
Died 16 August 2010 (aged 75)
Rome, Italy
Nationality Italian
Fields Particle physics
Institutions Italian National Institute of Nuclear Physics
Known for Cabibbo angle
Notable awards Sakurai Prize (1989)
Matteucci Medal (2002)
P.A.M. Dirac Medal (2010)

Nicola Cabibbo (10 April 1935 – 16 August 2010[1]) was an Italian physicist, best known for his work on the weak interaction. He was also the president of the Italian National Institute of Nuclear Physics from 1983 to 1992, and from 1993 until his death he was the president of the Pontifical Academy of Sciences.[2] He was born in Rome.

## Work

The Cabibbo angle represents the rotation of the mass eigenstate vector space formed by the mass eigenstates $\scriptstyle{| d \rangle , \ | s \rangle}$ into the weak eigenstate vector space formed by the weak eigenstates $\scriptstyle{| d^\prime \rangle , \ | s^\prime \rangle}$. The rotation angle is θC = 13.04°.

Cabibbo's major work on the weak interaction originated from a need to explain two observed phenomena:

Cabibbo solved the first issue by postulating weak universality, which involves a similarity in the weak interaction coupling strength between different generations of particles. He solved the second issue with a mixing angle θC (now called the Cabibbo angle), between the down and strange quarks. Modern measurements show that θC = 13.04°.

Before the discovery of the third generation of quarks, Cabibbo's work was extended by Makoto Kobayashi and Toshihide Maskawa to the Cabibbo–Kobayashi–Maskawa matrix. In 2008, Kobayashi and Maskawa shared one half of the Nobel Prize in Physics for their work. Some physicists had bitter feelings that the Nobel Prize committee failed to reward Cabibbo for his part.[3][4] Asked for a reaction on the prize, Cabibbo preferred to give no comment. According to sources close to him, he was very embittered.[5]

Recent work on evaluating the importance of scientific papers using Google's PageRank algorithm identifies Cabibbo's paper "Unitary symmetry and leptonic decays"[6] as the top ranked out of 353,268 articles published by the American Physical Society since 1893 in journals such as Physical Review Letters.[7] The same research shows that most of the authors of the top-ranked papers are also Nobel Prize winners, which makes Cabibbo's exclusion seem all the more curious.

Later, Cabibbo researched applications of supercomputers to address problems in modern physics with the experiments APE 100 and APE 1000.

Cabibbo supported attempts to rehabilitate executed Italian philosopher Giordano Bruno, citing the apologies on Galileo Galilei as a possible model to correct the historical wrongs done by the Church.[8]

After his death in 2011, the Franklin Institute awarded him with the Benjamin Franklin Medal in Physics.[9]

## Death

He died from respiratory problems in a Rome hospital on August 16, 2010 at the age of 75.

## References

1. ^ "Morto il fisico Cabibbo Gli fu negato il Nobel". Corriere della Sera. 16 August 2010. Retrieved 2010-08-16. (Italian)
2. ^ Maiani, L. (2010). "Obituary: Nicola Cabibbo (1935–2010)". Nature 467 (7313): 284. doi:10.1038/467284a. PMID 20844530.
3. ^ 闫同民 (2013). "与2008年诺贝尔物理奖失之交臂的物理学家". 物理双月刊 35. pp. 354–357.
4. ^ Valerie Jamieson (7 October 2008). "Physics Nobel snubs key researcher". New Scientist. Retrieved 2009-11-06.
5. ^ "Nobel, l'amarezza dei fisici italiani". Corriere della Sera. 7 October 2008. Retrieved 2009-11-06. (Italian)
6. ^ Nicola Cabibbo (1963). "Unitary symmetry and leptonic decays". Physical Review Letters 10 (12): 531–533. Bibcode:1963PhRvL..10..531C. doi:10.1103/PhysRevLett.10.531.
7. ^ "How Google’s PageRank predicts Nobel Prize winners". 21 January 2009. Retrieved 2009-11-06.
8. ^
9. ^ "Benjamin Franklin Medal in Physics". Franklin Institute. 2011. Retrieved December 23, 2011.