Early life and education Sakata was born in
Tokyo, Japan, on January 18, 1911, to a family that held a tradition of public service. He was the eldest of six children of Tatsue Sakata and . At the time of Sakata's birth, Mikita was secretary to Prime Minister
Katsura Tarō, who became Sakata's godfather. While attending Kōnan Middle School in
Hyōgo Prefecture in 1924, Sakata was taught by the physicist
Bunsaku Arakatsu. As a student at Kōnan High School from 1926 to 1929, Sakata attended a lecture by the influential physicist
Jun Ishiwara. Sakata also became closely acquainted with Katō Tadashi, who later co-translated
Friedrich Engels's 1883 unfinished work
Dialectics of Nature into Japanese. According to Sakata,
Dialectics of Nature and
Vladimir Lenin's 1909 work
Materialism and Empirio-criticism became formative works for his thinking.
Higher education and career Sakata got into the
Kyoto Imperial University in 1930. When he was a second-year student,
Yoshio Nishina, a granduncle-in-law of Sakata, lectured on
quantum mechanics at the Kyoto Imperial University. Sakata became acquainted with
Hideki Yukawa and
Shin'ichirō Tomonaga, the first and second Japanese Nobel laureates, through the lecture. After graduating from the university, Sakata worked with Tomonaga and Nishina at Rikagaku Kenkyusho (
RIKEN) in 1933 and moved to
Osaka Imperial University in 1934 to work with Yukawa. Yukawa published his first paper on the
meson theory in 1935, and Sakata closely collaborated with him to develop the meson theory. Possible existence of the neutral nuclear force carrier particle Pion| was postulated by them. Accompanied by Yukawa, Sakata moved to Kyoto Imperial University as a lecturer in 1939. Sakata and Inoue proposed their two-meson theory in 1942. At the time, a charged particle discovered in the hard component cosmic rays was misidentified as Yukawa's meson (Pion|, nuclear force career particle). The misinterpretation led to puzzles in the discovered cosmic ray particle. Sakata and Inoue solved these puzzles by identifying the cosmic ray particle as a daughter charged fermion produced in the decay. A new neutral fermion was also introduced to allow decay into fermions. We now know that these charged and neutral fermions in the modern language correspond to the second-generation leptons μ and . They then discussed the decay of the Yukawa particle, : Sakata and Inoue predicted the correct spin assignment for the muon and introduced the second neutrino. They treated it as a distinct particle from the beta decay neutrino, and correctly anticipated the muon's three body decay. The English printing of Sakata-Inoue's two-meson theory paper was delayed until 1946, one year before the experimental discovery of π → μν decay. Sakata moved to
Nagoya Imperial University as a professor in October 1942 and remained there until his death. The university's name was changed to Nagoya University in October 1947 after the end of the Pacific War (1945). Sakata reorganized his research group in Nagoya to be administered under democratic principles after the War. Sakata stayed at the Niels Bohr Institute from May to October 1954 at the invitation of
N. Bohr and
C. Møller. During his stay, Sakata gave a talk introducing works of young Japanese particle physics researchers, especially emphasizing an empirical relation found by Nakano and Nishijima, which is now known as the
Nakano-Nishijima-Gell-Mann (NNG) rule among the strongly interacting particles (hadrons). After Sakata returned to Nagoya, Sakata and his Nagoya group started research, trying to uncover the physics behind the NNG rule. Sakata then proposed his
Sakata Model in 1956, which explains the NNG rule by postulating that the fundamental building blocks of all strongly interacting particles are the
proton, the
neutron, and the
lambda baryon. The positively charged pion is made out of a proton and an antineutron, in a manner similar to the Fermi-Yang composite Yukawa meson model, while the positively charged kaon is composed of a proton and an anti-lambda, succeeding in explaining the NNG rule in the Sakata model. Aside from the integer charges, the proton, neutron, and lambda have similar properties as the
up quark,
down quark, and
strange quark, respectively. In 1959, Ikeda, Ogawa and Ohnuki and, independently, Yamaguchi found out the
U(3) symmetry in the Sakata model. The U(3) symmetry provides a mathematical description of hadrons in the
eightfold way idea (1961) of Murray Gell-Mann. Sakata's model was superseded by the
quark model, proposed by Gell-Mann and
George Zweig in 1964, which keeps the U(3) symmetry. However, it made the constituents fractionally charged and rejected the idea that they could be identified with observed particles. 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 Groups for Pedestrians" (1965). The Sakata model and its
SU(3) symmetry were also explained in the textbook
"Weak Interaction of Elementary Particles",
L.B.Okun (1965). In 1959, Gamba, Marshak, and Okubo found that Sakata's baryon triplet (proton, neutron, and lambda baryon) bears striking similarity to the lepton triplet (neutrino, electron, and muon) in the weak interaction aspects. To explain the physics behind this similarity in the composite model framework, in 1960, Sakata expanded his composite model to include leptons with his Nagoya University associates Maki, Nakagawa, and Ohnuki. The expanded model was termed “Nagoya Model”. Shortly thereafter, the existence of two kinds of neutrinos was experimentally confirmed. In 1962, Maki, Nakagawa, and Sakata and Katayama, Matumoto, Tanaka, and Yamada accommodated the two distinct types of neutrino into the composite model framework. In his 1962 paper with Maki and Nakagawa, they used the Gell-Mann-Levy proposal of modified universality to define the weak mixing angle that later became known as the Cabibbo angle. They extended it to the
leptons, clearly distinguishing neutrino weak and mass eigenstates, thus defining the neutrino flavor mixing angle and predicting neutrino flavor oscillations. The neutrino flavor mixing matrix is now named
Maki–Nakagawa–Sakata matrix. The nontrivial neutrino mixing introduced in the Maki–Nakagawa–Sakata paper is now experimentally confirmed through the
neutrino oscillation experiments. == Influences ==