Nicola Cabibbo
Born	10 April 1935 Rome, Italy
Nationality	Italian
Fields	Particle physics
Institutions	Italian National Institute of Nuclear Physics Pontifical Academy of Sciences
Known for	Cabibbo angle

Nicola Cabibbo (born 10 April 1935) is 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 since 1993 he has been the president of the Pontifical Academy of Sciences. He was born in Rome.

[edit] Work

The Cabibbo angle represents the rotation of the mass eigenstate vector space formed by the mass eigenstates into the weak eigenstate vector space formed by the weak eigenstates . The rotation angle is θ_C = 13.04°.

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

• The transitions between up and down quarks, between electrons and electron neutrinos, and between muons and muon neutrinos had similar likelihood of occurring (similar amplitudes); and
• The transitions with change in strangeness had amplitudes equal to one fourth of those with no change in strangeness.

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 θ_C (now called the Cabibbo angle), between the down and strange quarks. Modern measurements show that θ_C = 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.^[1] Asked for a reaction on the prize, Cabibbo preferred to give no comment. According to sources close to him, he was very embittered.^[2]

Recent work on evaluating the importance of scientific papers using Google's PageRank algorithm identifies Cabibbo's paper "Unitary symmetry and leptonic decays"^[3] as the top ranked out of 353,268 articles on physics published since 1893.^[4] 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.

More recently, Cabibbo has been researching applications of supercomputers to address problems in modern physics with the experiments APE 100 and APE 1000.

Cabibbo has supported attempts to rehabilitate executed Italian pantheist philosopher Giordano Bruno, citing the apologies on Galileo Galilei as a possible model to correct the historical wrongs done by the Church.^[5]

[edit] References

[edit] External links

Wikiquote has a collection of quotations related to: Nicola Cabibbo

• Cabibbo biography from the Istituto e Museo di Storia della Scienza (Italian)