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The Strongest

This article by one of the co-discoverers of 'the ' of classifying strongly interacting , first appeared in 'Science Year 1968' and is reproduced here by kind permission of the publishers.

Yuval Ne'eman by K. Unser. It has two channels, one for When that visionary, Jules Verne, described the search for an understanding of it is high and one for low frequencies, each the launching of the first manned space the greatest challenge in . with its own beam current transformer, flight in his science fiction novel 'From At Serpukhov, Russia, on the other side and the channels are coupled in such a the Earth to the Moon' in 1865, he calcu­ of the earth from the Saturn's base on way that there is an automatic and con­ lated the height of Captain Barbicane's Merritt Island, Florida, is the world's largest tinuous transition between the two to cover monstrous gun, the 'Columbiad', at 880 accelerator. Its proton beam acts the whole range. feet. When the gunpowder that filled a like the first stage in a multi-stage rocket. Beam current transformers for moni­ quarter of this gun was ignited, the space But each proton in the beam is boosted toring fast ejected beams have been capsule, in an earth-shattering blast, shot to 50 million times the it would developed by S. Battisti and R. Bertolotto. instantly to the 36 000 foot-per-second take to lift it#to the moon. It has 76 000 (At the synchro-cyclotron, R. Hohbach and velocity required to escape the earth's million (76 000 MeV) of S. Mango have achieved monitors of high . It was a jolting beginning to a kinetic energy. Remembering the Saturn's sensitivity — down to about 0.5 LIA — for remarkable lunar voyage. energy needs, it is obvious that physicists the extracted proton beam.) The particular studying this stronger force, needing so In 1968, Verne's prophecy has become problem with ejected beams is the low much more energy, must settle for an reality. Men of another century were con­ beam current and an accurate device for extremely small payload. When a small structing the Saturn V moon rocket, the slow ejected beams with a long spill-time bunch of strikes a metal target, most powerful machine ever built, to send has not yet been operated. the collision produces a multitude of tiny an Apollo spacecraft soaring to the moon. More difficulties come in when faced new particles called , , and To overpower gravity's enormous re­ with the problem of monitoring the beam . These are separated and sistance, the Saturn's engines burn almost in storage rings. The aim is to provide a collected in secondary beams, which are 4 000 gallons of fuel and oxidizer every monitor for the ISR which will be capable sent to destinations located deep within second. both of measuring the total stacked beam the nucleus of the . current (with values up to 20 A circulating Man has thus learned how to overcome Even as man explores the moon, so for many hours) and which will also be gravity — the gross force of afl the earth's will particles in those secondary beams sensitive to small changes, so that the . But within each small atom, there explore a new world — the world of the addition of an extra pulse (say 50 mA) is a much larger force — electromagnet- strong nuclear force. Physicists call it from the PS during the stacking process ism. Imagine that tiny rocketeers living the . It binds together can be monitored, and so that any beam within an atom wished to launch a nega­ and protons in atomic nuclei. Its losses can be detected. A paper on this tively charged against the electro­ pull, for particle, is more than a by Unser entitled 'Beam Current magnetic pull of its positively charged hundred times stronger than electro- Transformer with D.C. to 200 MHz Range' . They would need 10 000 magnetism, and a hundred followed by was read at the 1969 times more fuel than the amount needed 35 zeros times stronger than gravity. to lift a single electron from the earth to Conference at Washington on 7 March. These — gravitation, electro- the moon. To further illustrate the strength The response of the monitor is extended magnetism, and the strong nuclear force of this force, imagine that a Space Age to the d.c. condition (to measure the (plus a little-understood weak nuclear imp had removed all the from steady stacked beam in the ISR) by adding force) — cause all of the variety, change, only one-tenth of a cubic millimeter of the a magnetic modulator to the system and beauty in the . Without them, Apollo capsule's metal skin and had already used on the PS (which measures objects would never be aware of one carried them down to the launch pad. the rapid changes). It consists of a pair another. They would never attract or repel, The electromagnetic force now attracting of toroids which are excited by an aux­ and they would not collide, but would the positively charged capsule to the iliary oscillator in opposite senses so that effortlessly pass through each other. How electrons on the ground would be so their signals, in a winding around both do forces, which somehow act through overwhelming that, at blast-off, the toroids, cancel. When a beam passes what seems to be empty space, account 7 500 000 pound thrust of the Saturn's through, it introduces an asymmetry giving for this ? One of the great theoretical fiery engines could not budge the space­ an output signal proportional to the current. achievements in physics tells us the craft. The imp, to the bewilderment of the A prototype has given very encouraging answer, and allows us to see how the astronauts, would have matched the gravi­ results. It has been tested up to currents strong nuclear force — the strongest tational force of the whole earth with of 20 A and over a wide frequency range force — behaves. only a millionth of a gram of electrons. down to d.c. The accuracy was about 0.01 %>. When electrons violently collide, as they Within the nucleus of the atom there do in the sun or in the hot filament of is a force even stronger than electro- a light bulb, small bundles of kinetic magnetism. Scientists have known of this energy are knocked free. The electrons force for just over 30 years, and, today, slow down, due to dispersion of some

69 l/l/e can detect a proton only through its forces. It is the sum of four effects. The gravitation force, surrounding all matter in all directions to infinity, controls the stars and galaxies. The much stronger electromagnetic force cancels out at long range, since there are equal numbers of positive and negative charges in the universe. It controls the world of atoms and . The weak nuclear force is known to exist, but its carrier has not yet been detected. The strongest force — the strong nuclear force — controls most effects in the compacted nuclear and sub- nuclear world.

of green light, 2 x 1CT6 MeV of massive particle. He first assumed that energy, can-be observed only if it exists the new force could not spread faster than longer than a million-billionth (10-15) of light, which was not proved experimentally a second of time. When this photon exists until 1967 by Seymour Lindenbaum at for a shorter time, it cannot be detected. Brookhaven National Laboratory. A pho­ No photon having measurable energy ton moves 1 fermi in 10-tri I Months of a can be emitted by a static charge on my trillionth (10~23) of a second. Yukawa then shirt, but unobservable can freely used the uncertainty principle to calculate emerge from it at the speed of light and the minimum energy of a act on a hair. Thus, a stream of 'virtual' that can act only tjpis very short amount photons — so called to distinguish them of time. He found it to be about 100 MeV, from the 'physical' photons that we can roughly one-ninth of the energy — and observe — carries the charges' attraction thus one-ninth of the mass — of a or repulsion. The less energy a virtual nucléon. This hypothetical force-carrying photon has, the longer the time it can act. particle was called a . Thus the farther apart two charges are, Scientists could hope to check Yukawa's the longer the virtual photons take to leap theory by producing physical, rather than between them, the smaller the energy the virtual, in violent collisions be­ photons can possess, and the weaker the tween nucléons, just as physical photons force they transmit. The electromagnetic emerge from collisions of electrons. With force has an infinite range ; infinitely weak their sizable mass, the new mesons virtual photons reach out from each charge should, in fact, be easier to observe. to the very horizon of the universe. Further, when scientists had bombarded This also holds for the gravitational nuclei with neutrons, they found the force force. Its action is transmitted, also at that scattered the neutrons had turned the speed of light, by particles of energy some of them into protons, leaving the called . Though virtual when corresponding nuclei with one less positive simply binding the earth to its orbit around charge. Yukawa's force-carrying meson, it seemed, could carry an electric charge of their kinetic energy. These energy the sun, they are, according to theory, as well. A charged meson would expose bundles, called photons, carry the electro­ emitted physically whenever matter is a photographic emulsion, leaving a charac­ magnetic force that moves electrons in accelerated. Gravitons must be exceedingly teristic track, or it would leave a trail of your eye — and you can see. feeble. They have never been observed. droplets behind it as it passed through Photons, then, should also carry the a . Physicists hurried to force that exists between two charged The principle of uncertainty neatly study cosmic ray collisions, since protons particles even when neither is moving. explains the repulsions and attractions arriving from outer space would have Although the static charge on a too-easy- between charged particles and the gravi­ enough kinetic energy to materialize to-charge nylon shirt often is a nuisance, tational attraction between all masses. But mesons. it is scientifically illuminating. For the when the was discovered in It took 14 years, though, to confirm charge is not moving and can have no 1932, it soon became clear that still Yukawa's prediction. First, a particle was kinetic energy, yet it does emit photons. I another force must bind them to other discovered that had very nearly the know of them because they make the hair neutrons and protons in the nucleus. The predicted mass, 106 MeV. This particle, on my arm stand up. I cannot see these neutron carries no electric charge, and called a mu-meson, or '', was photons, however, even when I am using gravity is far too weak. In 1935, Japanese thought to be Yukawa's particle for a the finest laboratory instruments. physicist suggested the number of years. But in 1949, Soicho A powerful principle of physics, the new force, based upon the observation Sakata and Tokuzo Inoue in Japan and principle of uncertainty, explains why we that its range is extremely short. Indeed, at Cornell University and can observe some photons as lumps of the pull of the nuclear force comes to Robert Marshak at the University of energy but not detect the energy of other an abrupt end at a distance of only 1 Rochester explained that the muon simply photons at all. A photon is the smallest fermi (a 10-trillionth of a centimeter) from did not have anything to do with the strong amount of energy that we can measure. the centre of both neutrons and protons — force. It was not really a meson. Shortly We must wait for all its energy to pass the two varieties of the nucléon (the heavy afterwards, the right particle, the pi-meson, by us or see none of it. A definite amount particle that makes up all atomic nuclei). was found. This '' had a mass of of time, then, depending on the energy of Recalling that virtual photons carry 140 MeV, somewhat heavier than Yukawa's the photon, is needed to detect it. The electrical forces, Yukawa conjectured that prediction. Further, the pion materialized principle says, for example, that a single the nuclear force carrier should be a in three states — positively charged,

70 When a high-speed pion strikes a proton, many Strange K-mesons can bond strange in new particles emerge. Since the K+ meson, for ordinary nuclei to make hypernuclear atoms. instance, physically exists longer than its expected In tritium, scientists have replaced a neutron with life of 10~23 second, it must possess a new a lambda particle. property, called , that prevents its strong-force decay into two nonstrange pions. The permits the decay, but takes 100 trillion times as long.

negatively charged, and neutral. Three and its scientists, came out openly with states were necessary to explain why the an accusation of plagiarism. This was strong forces between two protons, be­ countered by Marshak in an intelligent and tween two neutrons, and between a neu­ touching answer. The entire exchange was tron and a proton are equal. The light (in published in the conference proceedings. weight) particles, called (electrons, Hopefully, this freeing of inner tensions in , , and photons) do not the scientific body will have cleared the 'feel' the pion's strong force. The pion atmosphere. and all heavier particles, which sense its strong force and interact through it, have been named . One might have thought that with the discovery of the pion, the strong force had yielded its secret. But the uncertainty The pion story did not develop without principle tells us that other mesons having inflicting a few wounds. It is said that higher masses may lurk unobserved deep Baron Ernest C. G. Stueckelberg Breiden- within the nucléon. The pion turned out to bach, a Swiss physicist, had had the same be just a beginning, in keeping with a 'law' idea as Yukawa in 1935. He checked it, of nature. Each time a major advance is however, with the renowned Austrian made and a mystery solved, we are quickly physicist Wolfgang Pauli, who ridiculed it. confronted by a new mystery. Thus, shortly Pauli apparently tended to be too critical after the discovery of the three pions of ideas that were not his own. In any seemed to completely explain the strong case, Stueckelberg did not publish his nuclear force, scientists were shocked to idea — and thus did not share the Nobel discover four heavier mesons. These K- prize in physics that was awarded to mesons, or kaons, at 500 MeV, were also Yukawa in 1949. produced by cosmic rays. Another sequel relates to the muon- At about the same time, other new pion error. Because of World War II and particles, similar to protons and neutrons, the lack of scientific communications that were discovered in cosmic ray tracks. followed it, the West had not noticed the Called baryons, they were heavier than new baryons ? And why do they live so Sakata-lnoue paper, and singled out Bethe the nucléon, and decayed into nucléons long ? The behaviour of these particles, and Marshak as the scientists who pointed and pions, or nucléons and leptons. matter that seemed to have no reason to out the mistaken identity. This created Strong-force decays always occur in exist, was explained in 1953 by Murray bitterness in Japan where it mixed with roughly the lifetime of virtual pions, about Gell-Mann, then at the University of pro-Communist leanings and resentment 10~23 second. Kaons carried the strong Chicago, and, independently, by Kazuhiko over the wartime defeat. The bitterness force just like pions, gluing nucléons to Nishijima in Japan. exploded at a conference held in 1965 at the new baryons but not to nucléons. But The new particles must have a new Kyoto, Japan, to commemorate the 30th these new particles all lived 10-10 second, characteristic that is not affected by the anniversary of Yukawa's theory. Mitsuo more than a trillion times longer than the strong force. Gell-Mann called it strange­ Taketani, one of the most respected of strong force would take to decay them. ness. The new baryons, he said, each had Japanese physicists, nursing personal and This was a real puzzle. Why were kaons, one unit of strangeness, and were thus political grudges against the United States rather than pions, virtually emitted by the unable to virtually emit, or decay into, familiar nonstrange particles in 10~23 second. The weak nuclear force apparently allowed strangeness to change by one unit at a time, permitting these strange particles to decay. Its weak accelerations slow the decay rate, however, and the particles live 10"10 second, long enough to leave tracks in film or in a cloud chamber.

Strangeness had just managed to explain the role of kaons when experiments carried out by Robert Hofstadter at Stan-

71 The single unit of of the rho-meson, left, is conserved, forcing the two spin 0 pions into which it decays, right, to spin around each other. The detection of orbiting pions first indicated the existence of the rho.

ford University and Robert Wilson at identical particles is always attractive if In 1961, Nambu's theory was confirmed Cornell University provided the next the spin of the exchanged meson is even. when researchers using particle acceler­ mystery. Yukawa had said that a nucléon The pion has spin 0. The best example of ators found indirect but certain evidence should be surrounded by a cloud of a pionlike force is simple Newtonian of a physical . Several other virtual pions out to a distance of 1 fermi. gravitation. It does not carry any twisting spin 1 mesons were similarly detected. Hofstadter and Wilson hoped to observe force ; two masses are simply pulled closer Attempts to measure the strength of the the cloud by seeing nucléons in atomic together along a straight line between strong force still deeper in the nucléon nuclei deflect high-energy electrons. Al­ them. Albert Einstein, in his 1916 theory turned, during the 1960s, to the high though electrons cannot sense the strong of the gravitational force, better known energy domain — the region where more force carried by a negatively charged under the mystifying name of the general massive virtual barygns and mesons should pion that is virtually emitted by a neutron, theory of relativity, showed, however, that be materialized by cosmic rays and, per­ they should sense the virtual photons from gravity is really carried by a spin 2 parti­ haps, by beams from powerful new the pion's electrical charge. cle, the . Attraction is only one accelerators. Mesons having two units of The electron probes did find a cloud, aspect of gravity. The graviton's spin spin were discovered between 1962 and but one that Yukawa's theory could not creates other effects : centrifugal force, 1964. The strong force, about Vio fermi wholly explain. Yoichiro Nambu, a Japa­ formerly explained by inertial mass, now from the centre of a nucléon, is dominated nese physicist working at the University known to be the same as gravitational by these heavy spin 2 mesons, even of Chicago and one of the deepest thinkers mass, and the coriolis force that holds a stronger in their attractive force than the in particle theory, showed in 1957 that bicycle upright when its wheels are pion. virtual pions could be decay products of spinning. yet another virtual meson having entirely is transmitted by a different features. This parent meson, spin 1 meson, the photon. This force, I sometimes wonder at the fantastic called the rho, would have about five carried by an odd-spin meson, is repulsive promise of the strong force. The whole times a pion's mass and would decay into between identical particles. The whole of of present technology — chemical, electri­ two pions deep within the nucléon by the magnetism — the twisting force around a cal, and mechanical engineering — is strong interaction. Nambu showed that if moving electron that causes an electric based upon only two relatively weak the rho was spinning, the two pions, which motor to turn — is due entirely to the forces, electromagnetism and gravitation. cannot spin themselves, would have to photon's spin. Now we see that the strong interaction come out orbiting around each other. Their The spin 1 of the new rho-meson would has, at various ranges, all these effects orbital motion would solve the mystery of imply that it, too, exerts a twisting force and more. We shall further see that these the Hofstadter-Wilson- cloud. similar to magnetism. And the force that forces all come in eights — eight simple The spin of the rho tells us something it carries between similar hadrons would be attractive potentials, eight complex forces more. A particle's rotation around its axis repulsive, as in the case of electric forces. resembling electromagnetism, eight times — spin — can have only specific values. This would explain why neighbouring a gravitation-inertialike force. What rich­ The electron, nucléon, and certain - nucléons in a nucleus, pulled toward each ness when someday engineers will be like particles are considered to have spins other by virtual pions, do not fall into able to exploit the regions under one of V2 units. Some heavier nucleonlike each other. Their central cores of virtual fermi. Can this prospect be more remote particles have spin 3h or spin V2. Force- rhos prevent it. Nucléons and their oppo­ than Jules Verne's vision of space travel carrying mesons have a different kind of site equivalents, antinucleons, however, a century ago ? spin 0, 1, 2, 3. Which spin they have are attracted together by the pions, and, determines the nature of the force they being opposites, are attracted by the rhos carry. For instance, the force between as well. They annihilate themselves. The high-energy studies have shown, as well, that as the energy goes up, the chance of two nucléons scattering each other steadily goes down. Will it, at infinite , take a limiting value, perhaps corresponding to the geometrical 'size' of the nucléons themselves ? Or will the chance of collision vanish alto­ gether and the particles become com­ pletely transparent to each other ? The most recent studies show that at the very highest energies, the strong force is dominated by a meson named for Isaak Ya Pomeranchuk, a Russian physicist who died in 1966. The nature of this 'pom- eranchukon' is a mystery. It could be a regularities, Darwin could trace descents. spin 2 meson, the lightest among them, Sir Isaac Newton's theory of gravitational called the f°, at 1250 MeV. It could, and inertial forces could come only after however, be a different effect, perhaps regularities and similarities in the motion the attraction due to the virtual emission of planets and falling objects had been of mesonlike proton- pairs, or discovered by Johannes Kepler and other particle- pairs emitted Galileo Galilei. and reabsorbed at distances smaller than Early in 1961, Murray Gell-Mann and I Vio fermi. independently suggested a scheme that Whether the pomeranchukon is this classified strongly interacting particles into special object, or the f°, will have im­ family groups. Previous attempts had portant implications for future space travel. failed. All the hadrons simply did not fit. According to relativity theory, as a space­ One scheme had come close to success, ship nears the speed of light, the astro­ however. It was based upon an idea of nauts' bodily processes imperceptibly Sakata's, in 1956, that the proton, the slow down. They could make hundred- neutron, and a , the lambda year trips to stars a hundred light-years , plus their , were the away in what to them would be just a few basic building blocks of all particles, and years. At these speeds, however, the ship thus of all matter. In 1960, Yoshio Ohnuki would constantly encounter in Japan and Walter Thirring in Austria atoms floating sparsely in interstellar uncovered a 19th century mathematical space. If the pomeranchukon is the special technique known as SU (3) — for Simple object, two protons moving toward each Unitary group of transformations in 3 other would always have a chance to complex dimensions. This SU (3) is an collide, even at the highest energies. especially good tool for manipulating Hydrogen in space would hit the ship groups of three basic objects. They found extremely hard, like cosmic rays, and this that by combining Sakata's charged parti­ intense could be one of the cle, neutral particle, and strange particle strongest reasons against the hope of in various ways, all the known properties travelling to the stars. of hadrons could be explained. Forces carried by pions and rho-mesons alterna­ tely attract and repel nucléons in an atomic If, instead, the pomeranchukon is the The scheme predicted that mesons nucleus. Spin 0 pions keep the nucleus from f° meson, the chances of protons colliding having the same spin should arrange in flying apart ; spin 1 rhos keep it from collapsing. would diminish with every increase in groups of eight. Thus, the seven known The discovery of the spin 2 f° meson hints that their energy. At infinite energy, the strong spin 0 mesons — the three pions and the if nucléons could be squeezed beyond the force would vanish, and the protons would four strange kaons — should have an resistance of the rho forces, they would attract never collide. A spaceship and its occu­ eighth companion. At the University of each other with enormous force. This would not only release staggering amounts of usable pants could cruise extremely close to the London, in 1961, Abdus Salam and John energy, but should also produce a new kind of speed of light and be unaware of the C. Ward extended Ohnuki's eightfold pre­ matter. The rho's repulsion, however, does not hydrogen gas passing harmlessly through diction to the spin 1 mesons as well, and weaken fast enough to allow this attraction except them. The question of which is the correct suggested that the rho, if found, should when two nucléons glance off each other at high speed. view is one of many that will be answered likewise have seven spin 1 companions. by two giant accelerators to be completed Baryons, however, not having the whole- in the 1970s, one by the U.S. Atomic number spins of the mesons, fell into 3-, 6-, Energy Commission at Batavia, III., and and 15-member groups. Because Sakata the other by the European Organization had assumed that certain baryons, the for Nuclear Research (CERN) in Europe. neutral xi, for instance, were made by adding together three spin V2 baryons, they were predicted to have spin 3h, and While measurements of the strong force a more complicated structure than the gradually advance, another approach has nucléon. brought a much needed order into our At about the same time, and without picture of the nucléon. The situation is knowing of Sakata's theory, I was looking similar to that of natural history. Charles into the same problem. I hit upon the Darwin's theory of evolution emerged only adequacy of the eightfold scheme as the when the animal kingdom had been suf­ simplest mathematical structure that could ficiently classified. Noting similarities and classify the strong interactions. The same

73 Three kinds of objects, shown as coloured triangles, can be arranged into ten possible groups of three. In The Eightfold Way, each combination of three fictitious objects, called , makes a different baryon.

minus particle. Since then, only 20 or so omega-minus particles have been ob­ served. They have the right mass (about 1,680 MeV), charge, strangeness, and also, I hope, the right spin, since this has not yet been measured. Thus, The Eightfold Way worked. Since then, many other predictions of The Eightfold Way have come true, so that the theory has been adopted by most physi­ cists. From a particle's position in its family pattern, we can predict the relative strengths of the force between it and the various hadrons. The scheme even goes idea occurred to Gell-Mann, at the Cali­ relative simplicity of Sakata's scheme still beyond the strong force, explaining their fornia Institute of Technology (Caltech). attracted many physicists. weak force and electromagnetic inter­ Neither of us had any notion, however, of One clear-cut difference could be drawn. actions, too. But we still do not know using known particles as fundamental If our scheme was right, baryons having why The Eightfold Way should hold. 'bricks', as in the Sakata model. We spins of V2 should exist as a 10-member Today's Newton has not yet appeared. both felt free to arbitrarily arrange the family. Four had been discovered by Enrico existing particles in various patterns, Fermi in 1950. Another three, each with without concern for their building blocks, one unit of negative strangeness, were In 1964, Gell-Mann and Georg Zweig at and see which pattern best fit the obser­ reported in 1961. And, at the 1962 CERN Caltech suggested checking whether the vations. conference, held in Geneva, Switzerland, three fictitious particles we had used as We thus found, unlike Ohnuki and a pair with two units each of negative elementary really exist as virtual or physi­ Thirring, that, of all mathematically pos­ strangeness was reported. Their spins cal particles. Gell-Mann called them sible structures, the arrangement of the were not known. If these nine really made quarks. In four years of searching, how­ eight then-known baryons into one family up a family, the 10th member should have ever, they have not been found, and the best explained the facts. Mathematically, three units of negative strangeness. More­ chance that they exist seems to be this meant that we had used three fictitious over, all nine decayed by the strong dwindling. objects as the building blocks, and made interaction in 10~23 second, and could be My own feeling is that the final theory all the baryons, including the nucléon, identified only by complex analyses of of matter and its strongest forces will not from various combinations of the three the decay products. Their 10th companion, have the naive simplicity of three truly types. In our 'synthesis', then, the xi though, could decay only by the weak elementary particles obeying the rules of would be no more complicated than the nuclear force, as its mass would be smaller The Eightfold Way. Nature will be more nucléon and would have the same V2 spin. than any decay products having the same clever. Indeed, if quarks are ever found, Our theory also predicted the existence strangeness. It should thus live about 10"10 I am sure that we shall be faced with an of eight spin 0 and eight spin 1 mesons. I second and leave a track in a bubble even deeper mystery. In 1968, a colleague published this, and so did Gell-Mann, early chamber. who has lived through the entire history in 1961. All the properties of the missing particle of elementary told me Within just a few months, the eighth could be predicted from our theory. Gell- that the first two high energy accelerators spin 0 meson was discovered. The eight Mann went to the blackboard during the — the at Berkeley, Calif., and spin 1 mesons were also found in 1961. In CERN conference and explained exactly the Cosmotron at Brookhaven, N.Y. — 1964, the spin 2 mesons were found, and what the experimenters should be looking both broke down shortly after they began arranged themselves neatly into the same for. I had made a similar suggestion the operating in 1954. Six months went by kind of octet. day before in a letter to Gerson Goldhaber before the experiments could be continued. and his late wife and collaborator, Sula- The Creator probably had given himself mith Goldhaber. An experiment with nega­ time to put some complexity into this Up to that point, it was not clear which tive results that they had reported just smallest of worlds that men were beginn­ theory was correct, the Sakata model — two days earlier had provided the last ing to explore. Let us not underestimate the more popular one — or 'The Eightfold needed clues, and I was trying to convince the sophistication He will be using next. Way', as Gell-Mann had named ours. them to look for the missing tenth piece Eight-member meson families had been of the puzzle. predicted by both models. The spin of In February, 1964, Nicholas Samios and From Science Year, The World Book the xi was found to be V2 in 1963 and 32 collaborators at Brookhaven National Science Annual. © 1968 Field Enterprises seemed to indicate we were right, but the Laboratory found it — the first omega- Educational Corporation.

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