Shoichi Sakata
Encyclopedia
was a Japanese
academic and physicist
who was internationally known for theoretical work on the structure of the atom. He proposed the Sakata model, which was an early precursor to the quark model
.
After the end of World War II, he joined other physicists in campaigning for the peaceful uses of atomic energy.
under Yoshio Nishina
and later at the Kyoto Imperial University
under Hideki Yukawa
, the first Japanese Nobel laureate. He first met Yukawa at Rikagaku Kenkyūsho in Ōsaka
, a private research foundation started by Yukawa. Here he worked with him from 1937 on meson
theory and in 1939 accompanied him to Kyoto University where Yukawa was a lecturer. Sakata was appointed professor at Nagoya University in 1942 and remained there until his death.
Sakata was a leading Japanese researcher in elementary particles in the 1950s and 1960s, and became well-known outside Japan for his 1956 model of hadrons, later termed the Sakata model, which proposed that the fundamental building blocks of all strongly interacting particles are the proton
, the neutron
and the lambda baryon. For example, the positively charged pion is made out of a proton and an antineutron. Aside from the integer charges, the proton, neutron, and lambda have the same properties as the up quark
, down quark
, and strange quark
respectively, explaining the model's success.
Sakata's model was superseded by the quark model
, due to Murray Gell-Mann
and George Zweig
, which made the constituents fractionally charged and rejected the idea that they could be identified with observed particles. This leads to the Gell-Mann–Nishijima formula
and the eightfold way
, which provides the most correct fundamental description. Still, within Japan, integer charged quark models parallel to Sakata's were used until the 1970s, and are still used as effective descriptions in certain domains.
Sakata's model was used in Harry J. Lipkin
's book "Lie Group
s for Pedestrians" (1965). In 1960, with his Nagoya University associates, he expanded his model to include leptons. Shortly thereafter he developed the Neutrino mixing matrix, a precursor to the currently accepted Neutrino oscillation
. In the early 1960s there was already evidence of a second neutrino type.
, Toshihide Maskawa
and Makoto Kobayashi
, who received their awards for work on symmetry breaking, all came under his tutelage and influence.. The Nagoya Model was the inspiration for the later Cabibbo–Kobayashi–Maskawa matrix of 1973, which specifies the mismatch of quantum states of quarks, when they propagate freely and when they take part in weak interactions. Physicists however, generally attribute the introduction of a third generation of quark
s (the "top" and "bottom" quarks) into the Standard Model
of the elementary particles to that 1973 paper by Kobayashi and Maskawa.
Kent Staley (2004) describes the historical background to their paper, emphasizing the largely forgotten role of theorists at Nagoya University and the "Nagoya model" they developed. Several of the authors of the Nagoya model embraced the philosophy of dialectical materialism
, and he discusses the role that such metaphysical commitments play in physical theorizing. Both theoretical and experimental developments that generated great interest in Japan, and ultimately stimulated Kobayashi and Masukawa's 1973 work, went almost entirely unnoticed in the U.S. The episode exemplifies both the importance of untestable "themata" in developing new theories, and the difficulties that may arise, when two parts of a research community work in relative isolation from one another.
Japanese people
The are an ethnic group originating in the Japanese archipelago and are the predominant ethnic group of Japan. Worldwide, approximately 130 million people are of Japanese descent; of these, approximately 127 million are residents of Japan. People of Japanese ancestry who live in other countries...
academic and physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
who was internationally known for theoretical work on the structure of the atom. He proposed the Sakata model, which was an early precursor to the quark model
Quark model
In physics, the quark model is a classification scheme for hadrons in terms of their valence quarks—the quarks and antiquarks which give rise to the quantum numbers of the hadrons....
.
After the end of World War II, he joined other physicists in campaigning for the peaceful uses of atomic energy.
Career
Between 1929 and 1933 Sakata studied physics in TokyoTokyo
, ; officially , is one of the 47 prefectures of Japan. Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the largest metropolitan area of Japan. It is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family...
under Yoshio Nishina
Yoshio Nishina
was the founding father of modern physics research in Japan. He co-authored the well-known Klein–Nishina formula. He was a principal investigator of RIKEN and mentored generations...
and later at the Kyoto Imperial University
Kyoto University
, or is a national university located in Kyoto, Japan. It is the second oldest Japanese university, and formerly one of Japan's Imperial Universities.- History :...
under Hideki Yukawa
Hideki Yukawa
né , was a Japanese theoretical physicist and the first Japanese Nobel laureate.-Biography:Yukawa was born in Tokyo and grew up in Kyoto. In 1929, after receiving his degree from Kyoto Imperial University, he stayed on as a lecturer for four years. After graduation, he was interested in...
, the first Japanese Nobel laureate. He first met Yukawa at Rikagaku Kenkyūsho in Ōsaka
Osaka
is a city in the Kansai region of Japan's main island of Honshu, a designated city under the Local Autonomy Law, the capital city of Osaka Prefecture and also the biggest part of Keihanshin area, which is represented by three major cities of Japan, Kyoto, Osaka and Kobe...
, a private research foundation started by Yukawa. Here he worked with him from 1937 on meson
Meson
In particle physics, mesons are subatomic particles composed of one quark and one antiquark, bound together by the strong interaction. Because mesons are composed of sub-particles, they have a physical size, with a radius roughly one femtometer: 10−15 m, which is about the size of a proton...
theory and in 1939 accompanied him to Kyoto University where Yukawa was a lecturer. Sakata was appointed professor at Nagoya University in 1942 and remained there until his death.
Sakata was a leading Japanese researcher in elementary particles in the 1950s and 1960s, and became well-known outside Japan for his 1956 model of hadrons, later termed the Sakata model, which proposed that the fundamental building blocks of all strongly interacting particles are the proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....
, the neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
and the lambda baryon. For example, the positively charged pion is made out of a proton and an antineutron. Aside from the integer charges, the proton, neutron, and lambda have the same properties as the up quark
Up quark
The up quark or u quark is the lightest of all quarks, a type of elementary particle, and a major constituent of matter. It, along with the down quark, forms the neutrons and protons of atomic nuclei...
, down quark
Down quark
The down quark or d quark is the second-lightest of all quarks, a type of elementary particle, and a major constituent of matter. It, along with the up quark, forms the neutrons and protons of atomic nuclei...
, and strange quark
Strange quark
The strange quark or s quark is the third-lightest of all quarks, a type of elementary particle. Strange quarks are found in hadrons, which are subatomic particles. Example of hadrons containing strange quarks include kaons , strange D mesons , Sigma baryons , and other strange particles...
respectively, explaining the model's success.
Sakata's model was superseded by the quark model
Quark model
In physics, the quark model is a classification scheme for hadrons in terms of their valence quarks—the quarks and antiquarks which give rise to the quantum numbers of the hadrons....
, due to Murray Gell-Mann
Murray Gell-Mann
Murray Gell-Mann is an American physicist and linguist who received the 1969 Nobel Prize in physics for his work on the theory of elementary particles...
and George Zweig
George Zweig
George Zweig was originally trained as a particle physicist under Richard Feynman and later turned his attention to neurobiology...
, which made the constituents fractionally charged and rejected the idea that they could be identified with observed particles. This leads to the Gell-Mann–Nishijima formula
Gell-Mann–Nishijima formula
The Gell-Mann–Nishijima formula relates the baryon number B, the strangeness S, the isospin I3 of hadrons to the charge Q. It was originally given by Kazuhiko Nishijima and Tadao Nakano in 1953, and lead to the proposal of strangeness as a concept, which Nishijima originally called "eta-charge"...
and the eightfold way
Eightfold way (physics)
In physics, the Eightfold Way is a term coined by American physicist Murray Gell-Mann for a theory organizing subatomic baryons and mesons into octets...
, which provides the most correct fundamental description. Still, within Japan, integer charged quark models parallel to Sakata's were used until the 1970s, and are still used as effective descriptions in certain domains.
Sakata's model was used in Harry J. Lipkin
Harry J. Lipkin
Harry Jeannot Lipkin , also known as Zvi Lipkin, is an Israeli theoretical physicist specializing in nuclear physics and elementary particle physics. He is a recipient of prestigious Wigner Medal.-Biography:...
's book "Lie Group
Lie group
In mathematics, a Lie group is a group which is also a differentiable manifold, with the property that the group operations are compatible with the smooth structure...
s for Pedestrians" (1965). In 1960, with his Nagoya University associates, he expanded his model to include leptons. Shortly thereafter he developed the Neutrino mixing matrix, a precursor to the currently accepted Neutrino oscillation
Neutrino oscillation
Neutrino oscillation is a quantum mechanical phenomenon predicted by Bruno Pontecorvowhereby a neutrino created with a specific lepton flavor can later be measured to have a different flavor. The probability of measuring a particular flavor for a neutrino varies periodically as it propagates...
. In the early 1960s there was already evidence of a second neutrino type.
Influences
The 2008 physics Nobel laureates Yoichiro NambuYoichiro Nambu
is a Japanese-born American physicist, currently a professor at the University of Chicago. Known for his contributions to the field of theoretical physics, he was awarded a one-half share of the Nobel Prize in Physics in 2008 for the discovery of the mechanism of spontaneous broken symmetry in...
, Toshihide Maskawa
Toshihide Maskawa
is a Japanese theoretical physicist known for his work on CP-violation who was awarded one quarter of the 2008 Nobel Prize in Physics "for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature."-Biography:A native of Aichi...
and Makoto Kobayashi
Makoto Kobayashi (physicist)
is a Japanese physicist known for his work on CP-violation who was awarded one quarter of the 2008 Nobel Prize in Physics "for the discovery of the origin of the broken symmetry which predicts the existence of at least three families of quarks in nature."- Biography :After completing his PhD at...
, who received their awards for work on symmetry breaking, all came under his tutelage and influence.. The Nagoya Model was the inspiration for the later Cabibbo–Kobayashi–Maskawa matrix of 1973, which specifies the mismatch of quantum states of quarks, when they propagate freely and when they take part in weak interactions. Physicists however, generally attribute the introduction of a third generation of quark
Quark
A quark is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. Due to a phenomenon known as color confinement, quarks are never directly...
s (the "top" and "bottom" quarks) into the Standard Model
Standard Model
The Standard Model of particle physics is a theory concerning the electromagnetic, weak, and strong nuclear interactions, which mediate the dynamics of the known subatomic particles. Developed throughout the mid to late 20th century, the current formulation was finalized in the mid 1970s upon...
of the elementary particles to that 1973 paper by Kobayashi and Maskawa.
Kent Staley (2004) describes the historical background to their paper, emphasizing the largely forgotten role of theorists at Nagoya University and the "Nagoya model" they developed. Several of the authors of the Nagoya model embraced the philosophy of dialectical materialism
Dialectical materialism
Dialectical materialism is a strand of Marxism synthesizing Hegel's dialectics. The idea was originally invented by Moses Hess and it was later developed by Karl Marx and Friedrich Engels...
, and he discusses the role that such metaphysical commitments play in physical theorizing. Both theoretical and experimental developments that generated great interest in Japan, and ultimately stimulated Kobayashi and Masukawa's 1973 work, went almost entirely unnoticed in the U.S. The episode exemplifies both the importance of untestable "themata" in developing new theories, and the difficulties that may arise, when two parts of a research community work in relative isolation from one another.
Honors
- Asahi PrizeAsahi PrizeThe Asahi Prize is a prize awarded by the Japanese newspaper the Asahi shimbun for achievement in scholarship or the arts that has made a contribution to culture or society. It was established in 1929. Many recipients of this prize have later been honoured with a Nobel Prize...
1948 - Imperial Prize of the Japan AcademyImperial Prize of the Japan AcademyThe was a prestigious honor conferred by the Imperial Academy from 1911 through 1945. The award was presented to non-members in recognition of their academic theses, books, and achievements....
1950 - Order of the Sacred TreasureOrder of the Sacred TreasureThe is a Japanese Order, established on January 4, 1888 by Emperor Meiji of Japan as the Order of Meiji. It is awarded in eight classes . It is generally awarded for long and/or meritorious service and considered to be the lowest of the Japanese orders of merit...
(瑞宝章 Zuihōshō) 1970