Nicola Cabibbo

Nicola Cabibbo
Born	(1935-04-10)10 April 1935 Rome, Italy
Died	16 August 2010(2010-08-16) (aged 75) Rome, Italy
Nationality	Italian
Fields	Particle physics
Institutions	Italian National Institute of Nuclear Physics Pontifical Academy of Sciences
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) 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. 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 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. Asked for a reaction on the prize, Cabibbo preferred to give no comment. According to sources close to him, he was very embittered.

Recent work on evaluating the importance of scientific papers using Google's PageRank algorithm identifies Cabibbo's paper "Unitary symmetry and leptonic decays" as the top ranked out of 353,268 articles published by the American Physical Society since 1893 in journals such as Physical Review Letters. 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.

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

Death

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

External links

• Cabibbo biography from the Istituto e Museo di Storia della Scienza (Italian)
• Parisi, Giorgio (2011). "Nicola Cabibbo". Physics Today 64 (2): 59. Bibcode:2011PhT....64b..59P. doi:10.1063/1.3554322. 

Catholic Church titles
Preceded by Giovanni Battista Marini Bettòlo Marconi	President of the Pontifical Academy of Sciences 6 April 1993 – 16 August 2010	Succeeded by Werner Arber