Cronin (Cronin), James W.( The American physicist, Nobel Prize in Physics, 1980)
Comments for Cronin (Cronin), James W.
Biography Cronin (Cronin), James W.
Genus. September 29, 1931
American physicist James Watson Cronin was born in Chicago (Illinois), the son of James Farley Cronin, while graduate students department of classical languages, University of Chicago, and Dorothy (Watson) Cronin. For Parents. met by attending a class in ancient Greek at Northwestern University. After a short stay in Alabama in 1939. family moved to Dallas (Texas), where his father to. became professor of Latin and Greek languages at Southern Methodist University to. attended local primary and secondary school in Highland Park, and then continued his education at Southern Methodist University, graduating in 1951, receiving a bachelor's degree in physics and mathematics.
Sam K. believes that his real education began in the autumn of 1951, when he became a graduate student at the University of Chicago. Among his teachers were Enrico Fermi, Maria Goeppert-Mayer, Edward Teller, Val Telegdi, Marvin Goldberger and Murray Gell-Mann. It Gell-Mann and arouse K. interest only if the emergent elementary particle physics. The degree of Doctor K. received in 1955 with a thesis in experimental nuclear physics, performed under the leadership of Samuel K. Allison.
Then K. joined Rodney Kula and Oreste Piccioni of Brookhaven National Laboratory on Long Island. These researchers have worked on the newly constructed cosmotron-accelerator capable to disperse protons to an energy of 3 billion. electronvolt. In Brookhaven K. met Val L. Fitch, who in autumn 1958. invited him to go to work at Princeton University. Through independent research programs, these two scientists in 1963. completed a joint, which became a classic experiment that blew seemed unshakable view of one of the laws of nature.
At one time, physicists believed that in nature there are three fundamental law of symmetry. According to the first law, known as the 'symmetry of charge conjugation' (C), the outcome of any physical experiment should remain unchanged, if every particle in the experiment to replace the corresponding anti-particle (ie. particle-twin, but with opposite electric charge and some other properties). In other words, a world composed entirely of antimatter would have to obey the same physical laws as the world consisting of matter. The second law - the 'conservation of parity' (P), contends that any reaction between the particles must remain the same if all the geometric quantities, such as spatial coordinates, replace them with a mirror image, ie. no reaction can distinguish right from left. The third law, 'symmetry under time reversal' (T), states that any reaction between elementary particles should occur equally well in forward and in reverse. For example, if two particles can coalesce, forming a third, the latter can decompose to form two initial particles.
In 1956, Mr.. Tszundao Lee and Chen Ning Yang came to the conclusion of a possible non-conservation of parity P in some reactions, . associated with weak interaction, . which is responsible for some forms of radioactive decay, . in contrast to the strong interaction, . confining particles inside the atomic nucleus,
. They proposed experiments that would resolve this issue. And soon By Tszyansyun and her staff of Columbia University proved that parity is not completely preserved in the beta decay (electron emission) of some radioactive nuclei:
. nuclei emit more 'left-oriented' electrons than 'right-oriented'
. Other researchers have found that the charge conjugation (C) is also preserved only approximately. In some physical processes revealed preference for particles to antiparticles. Physicists managed to save some semblance of order, combining the C and P in the combined law of conservation of CP-symmetry, which is confirmed by experimental results. Breach of compensated with a simultaneous violation of P, and vice versa. For example, if an excess of electrons levoorientirovannyh violates parity conservation, the simultaneous replacement of particles by antiparticles would make levoorientirovannye in pravoorientirovannye electrons and positrons would leave unchanged the physical laws. It is the universal conservation of the combined CP-symmetry, proposed to explain the irregularities in the individual P-and R-symmetries, and has been refuted by K. and Fitch summer 1963
To. and Fitch studied beams of neutral K-mesons, now known as kaons (particles with half as much weight than the proton) generated by the accelerator in Brookhaven. Start the experiment, scientists did not set ourselves the task to refute the CP-symmetry, on the contrary, they hoped to confirm its. However, in a series of experiments conducted with the participation of Rene Thurloe from the Center for Nuclear Research in France and James Christensen, graduate of Princeton, to. and Fitch discovered unconditional support CP-symmetry violation. In the decay of a certain kind of neutral K-mesons of about one event out of 500 does not satisfy the test for symmetry. The first confirmed violation of CP-symmetry was indirect; Subsequent experiments made this apparent effect. In the decays of K-mesons levoorientirovannye particles dominate over pravoorientirovannymi (violation of parity P), a matter over antimatter (violation of charge symmetry of C). In addition, the combined CP-symmetry is also violated in the decays levoorientirovannaya matter predominates over pravoorientirovannoy. This was manifested in the form of a prohibited type of decay. In accordance with the CP-symmetry short-lived neutral K-mesons to decay into two pi-meson, and long-lived neutral K-mesons (on average they are 500 times longer than the short-lived) can only decay into three pi-meson. Experimental results, which was met first with disbelief, before the publication was within six months subject to scrutiny and verification, which have convincingly shown that some long-lived K-mesons decay into two pi-meson.
. Above Suspicion remained only a general symmetry - a combination of all three symmetries CPT
. Any phenomenon that is observed in nature, has the property that the corresponding phenomenon that occurs while a replacement left and right, matter and antimatter and time reversal, should be equally probable. This fact and the violation of CP-invariance led to the conclusion: the symmetry under time reversal must be violated. If the CP-violating, then in order to CPT-symmetry is maintained, T-symmetry (with respect to time reversal) must be violated. The collapse of the K-meson CP-violating, can not be converted in time. These findings led scientists to rethink not only the previous explanations of physical phenomena, but also create a new theory of the evolution of the Universe. Indeed, if in the first moments of 'big bang' of matter and antimatter were formed in equal quantities, they could completely annihilate. But violation of CP-invariance allows antiparticles decay faster than the particles, and, therefore, is fast disappearing, leaving a surplus of particles in the form of matter in the Universe. As for the annihilation process, they will swell the supply of electromagnetic radiation in the universe.
In 1964, Mr.. K. became a full professor at Princeton University, but spent this year at the Center for Nuclear Research in France, working with Thurloe. The next year, to. returned to Princeton, where he continued to study violations of CP symmetry in the decays of K-mesons. In 1971, Mr.. He became a member of the Faculty of the University of Chicago, where experiments are carried out on a new accelerator, the Fermi National Accelerator Laboratory, located directly outside the city limits.
In 1980. K. and Fitch shared the Nobel Prize in Physics "for the discovery of violations of fundamental symmetry principles in the decay of neutral K-mesons'. At the conclusion of his Nobel lecture to. said: 'We must always remember that the violation of CP-symmetry, however little it may be the most realistic effect ... This effect suggests that between matter and antimatter exists a fundamental asymmetry, and that it indicates the possibility of manifestation of asymmetry under time reversal at the level of some weak interactions ... We hope that someday, and this mysterious message from nature will be deciphered. "
After receiving the Nobel Prize to. continues to work at the University of Chicago, where, in particular, trying to understand the root causes of the violation of CP symmetry.
In 1954, Mr.. K. married to Annette Martin, a graduate student, University of Chicago. They have three children. Their leisure time more often than he spends in a country house in Wisconsin, likes to make skiing.
In addition to the Nobel Prize, K. awarded "For scientific achievements' Research Corporation of America (1968), . Medals John Price Uezerilla Franklinovskogo Institute (1975) and an aide Ernest Orlando Lawrence Award in Physics of the Office of Energy Research and Development U.S. (1977),
. He is a member of the U.S. National Academy of Sciences, the American Physical Society and American Academy of Arts and Sciences.