CERN/285 25 September, 1958

ORGANISATION EUROPEENNE POUR LA RECHERCHE NUCLEAIRE

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH

ELEVENTH SESSION OF COUNCIL

Geneve. - 9 October, 1958

C E R N AND THE SECOND UNITED NATIONS INTERNATIONAL CONFERENCE ON THE PEACEFUL USES OF ATOMIC ENERGY

September 1-15, 1958 OCR Output

5592/G CERN/285

CERN AND THE SECOND UNITED NATIONS INTERNATIONAL CONFERENCE ON THE PEACEEUL USES OF ATOMIC ENERGY

September 1-15, 1958

CERN at the Scientific Exhibition

During the two weeks of activities of the Second United Nations International Conference on the Peaceful Uses of Atomic Energy, CERN was able greatly to benefit by the Conference, especially by showing the CERN laborato ries to a great number of scientists and other people and giving information on the international character of CERN.

This was brought about originally by a suggestion put forward by Professor C.J. Bakker, Director-General, to the Conference Secretary-General, Dr. Sigvard Eklund; Professor Bakker namely proposed that regular visits to CERN by the official delegates to the Conference be organized. Dr. Eklund in turn then invited CERN to participate in the Scientific Exhibition at the Palais des Nations, though this would have to be limited to a static, i.e. non-functional exhibit under the exhibition regulations, since CERN was not officially participating in the Conference.

Accordingly space was granted and a modest stand representing the activities of CERN was set up under the direction of the Public Information Office in the pavillon erected for the Scientific Exhibition.

This included a 1:5OO scale model of the CERN research centre as it will appear under the present programme when comple ted in 1960. Several photographs showing the manifold construc tion and research activities now going on in CERN were also dis played. The biggest of these was an aerial view, placed so that it could be compared directly with the model, thereby setting off the "present" against the "future". On the walls were the bilingual masthead of the Organization and a multicoloured nuclear representation of the flags of the l2 Member States showing the

5592/ .../... OCR Output CERN/285 Page 2

names of these States. Illustrated folders describing CERN, its aims and programme, were laid out daily. A small expla natory sign was also provided, telling exhibition visitors the procedure of application for the twice-daily visits to the site itself.

CERN was officially represented at the formal opening of the Scientific Exhibition on Sunday, August 5lst by the Director-General and the Public Information Office. During the protocol visit of the leading United Nations and other personalities, the United Nations Secretary-General, Mr. Dag Hammarskjold, the Under-Secretary Dr. Ralph G. Bunche and the President of the Conference Professor F. Perrin were for mally welcomed at the CERN stand. This ceremony was cinema tographically recorded and show on the television networks.

Finally it should be mentioned that, at the request Of the Director—General, the Secretary of the Conference, Dr. Eklund, made observer cards available to CERN so that the scientific staff of CERN had the opportunity to attend many sessions.

Conference visits to the Site

In accordance with the previously cited suggestion of Professor Bakker, arrangements were made by the Public Information Office for Conference participants to visit CERN. Twice—daily group visits were organized for every day from Monday, September lst to Saturday, September l5th. Bus transportation for these groups of 50 at a time was laid on by the United Nations Conference Secretariat, so that the visitors were able easily·to travel back and forth between the Palais des Nations and CERN. The 50 participants per group were in all cases exceeded, many arriving as additional visitors.

Each visit lasted between two and three hours and was in all cases preceded by a complete briefing, historical, tech nical and administrative, on the Organization. Altogether there were 22 visits in the officially scheduled series, of which 14 were conducted in English, 4 in French, 2 in Russian and 2 in Spanish. In addition, a large number of unscheduled visits, organized through the personnel of other Services in CERN, were conducted in English, French, Italian, German, Russian, Portuguese, Danish, Norwegian, Swedish, Serbo—Croati&n and Hebrew.

CERN Annual Reports for 1957 were handed out to all visitors as a scientific and sentimental souvenir of their visits.

Altogether more than l 2OO participants in the Conference were thoroughly briefed on CERN and were shown its facilities. OCR Output

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The CERN;];:meson decay experiment - a Conference Highlight

A major highlight of the Second United Nations Inter national Conference on the Peaceful Uses of Atomic Energy was provided by CERN at a midday press conference on Thursday, September 4th 1958, when Professor G. Bernardini, Director of Research of the CERN Synchro-cyclotron Division announced the crucial experiment on branching ratios cf’U'-meson - "JL—meson electron and direct'H —meson—electron decay performed by the CERN research team of T. Fazzini (Italy), G. Fidseare (Italy), A.W. Merrison (U.K.), H. Paul (Austria) and A.V. Tollestrup (U.S.A.), with the CERN 600 MeV synchro—cyclotron.

This experiment, the first critical research of basic theoreticalsignificance to be performed at CERN, was presented later the same afternoon in an unscheduled paper read by G. Fidecaro as the first at an informal session on fundamental particle physics, presided ever by Professor V. weisskopf with Professor A. Salam as Scientific Secretary. The news was indeed sensational, as can be seen from the concluding remarks at the end of the Second International Conference by Professor E. Perrin, Conference President and by Professor I.I. Rabi of Columbia University, New York, as well as from the accompanying transcripts of press comments by the scientific correspondents of major world newspapers.

Cgygegrgss Conference

The 0rganization's hitherto biggest Press Conference was held in the afternoon of Thursday, ll September, an open afternoon as regards the United Nations Conference, and a public holiday in Geneva. Invitations were sent out to all correspondents accredited to the Second United Nations International Conference on the Peaceful Uses of Atomic Energy. Over 140 scientific, technical and daily press journalists attended. Briefings on the Organization were held by the President of the Council, M. Erangois de Rose and by the Director—General, Professor C.J. Bakker. Dr. A. Merrison of the T?—meson decay experimental team also outlined the famous experiment and its theoretical significance. A press commu nique on the experiment was issued in French and English, and like wise sent to all journalists not attending.

This was followed by group visits of the journalists and correspondents to the site, and by cocktails and refreshments served on the lawn adjacent to the CERN canteen. OCR Output

5592/E cnaw/2s5 Page 4

Responses in the press are indicated by the appendices to this report, which are transcripts of a small number of the many press clippings so far received.

Newreels, television and radio

During the Conference various television, newsreeland documentary film producers seized the opgortunity to make films of CERN activities. Similar activities were also carried out by photographers for the daily and specialized press, and by the Danish radio.

One news fibnwas made of a scheduled visit by Conference delegates by the Ciné Journal Suisse.

The UFA—wochenschau also made a more complete cinematogra phic reportage of the official visit by Dr. Siegfried Balke, Minister for Atomic Affairs of the Gorman Federal Republic and a number of his collaborators. This included his welcome to CERN by the Presi dent of the Council and Professor Bakker, a,d various sequences of his visit afterwards. It was distributed throughout the world as a,newsreelimmediately. In Germany alone nine million people see the UFA-Wochenschau regularly every week.

Finally, a very detailed television and documentary film, with interviews in three languages, English, German and Italian, was made by the United Nations Visual Information Office; based around CERN and the ’H —meson decay branching ratio experiment.

A radio interview on CERN and the W\ —meson experiment was made for Danish listeners.

*¤ * *

The Second United Nations International Conference on the Peaceful Uses of Atomic Energy has been highly advantageous from the point of view of making CERN widely known to the parti cipants in the Conference and the Press. The CERN laboratory, in effect, became a third major Conference exhibit, in every way as successful as the Scientific Exhibition at the Palais des Nations and the Industrial Exhibition at the Pavillon des Sports, throughout the two weeks of the Conference.

•••/•••OCR Output CERN/285 Annex A

In his statement at the termination of the Conference

Professor l.l. Rabi, one of the original instigators of the

European Organization for Nuclear Research, alluded to CERN

in the following terms :

... An example of what can be accomplished in science by active collaboration of nations can be seen right here in Geneva. Under the stimulus of a resolution adopted by the General Assembly of Unesco in 1950 a European centre for nuclear research was set up in Geneva. This is the famous CERN laboratory. This great and expanding international institution is the result of the collaboration of twelve European nations banded together to provide research facilities in high energy physics. Owing to the great cost of some of these facilities they are beyond the capacity of any but the largest and wealthiest countries. When the burden is shared the problem is greatly reduced. Here in this laboratory, only a very short distance from the hall in which we are meeting, you will find scientists of many different nationalities, from many different regions of the world working happily together almost unconscious of differences of nationality. The great success of this laboratory is an inspiration to all of us and the embodiment of a hope that successful colla borative efforts can be expanded to other fields of science and, indeed, to other branches of human endeavour so that we may find in this arid world of strife living eases where people work together as people undistractod by tags of race or nationality ... OCR Output

5592 crew/2s5 Annex B

ln his closing address, Professor Francis Perrin, President of the Second United Nations International Conference on the Peace ful Uses of Atomic Energy and Member of the Council of CERN, stressed the crucial significance of the CERN WT-meson decay experim nent in these words :

"ln the field of basic physics, the most important news that reached us did not figure in our programme at all; it could not indeed have been included, because it concerns a very recent discovery.’lt was only during the course of our Conference that Dr. Bornardini and his fellow—workers at CERN announced that they had obtained definite proof of the exceptional direct dis integration of pions into electrons and neutrinos with out passing through the intermediate stage of mu—mosons. The failure of the attempts made hitherto to observe this direct disintegration created a serious difficulty in the theory of nuclear forces and beta radiation pro pounded more than 2O years ago by Professor Yukawa. It is a matter of special gratification for us, whose main concern is to develop scientific co-operation between nations, that this important discovery should have been node by an international team working in a laboratory and with a great machine built in our host City of Geneva as a result of the close association of a dozen countries .... OCR Output

5592 cram/2s5 Annex C

Amongst the numerous newspaper clippings concerning the

‘h —neson decay experiment — by no means all have yet come in the following may be quoted :

FIGARO ~ PARIS, September 12th, 1958 by Pierre de Latil, Scientific Correspondent

'... Midi. Cinq conferences de presse a la file. Une essentielle et presidee par M. Yukawa, grand physician japonais, qui predit le meson il y a vingt—trois ans. I1 nous dit son emotion de voir 1a recente experience du CERN confirmer ses theories : — Je doutais de noi et pourtant j'esperais que 1es faits finiraient par me donner raison — ..J

LE MONDE - PARIS, September 6th, 1958

"UNE IMPORTANTE DECOUVERTE SUR LA STRUCTURE DE LA MATIERE Geneve, 5 septenbre (A.F.P., U.P.I.).

"Une tres importante decouverte du comportement des particules elementaires a ete annoncée jeudi a la deuxieme cenférenee atomique internationale. Le Professeur Umberto Bernardini a fait connaitre que l'equipe qu'i1 dirige au Centre europeen de recher ches nucleaires vient de parvenir a etablir qu'un ’neson pi" subissait une transmutation et donnait un electron et un neutrino, Les mesons, electrons, neutrinos, etc., font partie des seize particules elementaires que 1'on connait ac tuellement, La decouverte du Professeur Bernardini — pour theo rique et abstraite qu'e11e soit — represents un grand pas en avant de la physique fondamentale. En effet, la transformation des "nesons PI" etait un des grands nysteres qui se posaient depuis vingt-trois ans aux physicians. C'est en 1955 qu'un savant japonais, 1e Professeur Yukawa, a ete, pour la premiere fois, anene a admettre, pour des raisons theoriques, 1'exis tence des mesons. Mais ces derniers ne furent mis en

5592/E OCR Output CERN/285 Annex C - 2

évidence au cours d’une experience qu’en 1947, M. Yukawa avait également prévu qu’une catégorie de ces particules, les "mésons PI", pouvaient donner naissance a un electron. Mais, des années durant, il resta impossible de procéder a une verification expérimentale, et d'autres theories virent le jour. C'est a une confirmation de la these de M. Yukawa que les savants du CERN viennent d’aboutir. Cette demonstra tion du hien—fondé des hypotheses formulées par le physi cien japonais présente une grande importance pour la connaissance des lois de la matiere. L'équipe du Professeur Bernardini est ccmposée de ME; Fazzini, Giuseppe Eidecaro (tous deux Italiens), Alex. herrison (Britannique), Paul (Autrichien) et Alven Tollestrup (Américain).'

MANCHESTER GUARDIAN, September 5th, 1958

"PRCEESSOR DANCES AT NEWS OF NUCLEAR DISCOVERY

from our Scientific Correspondent

"Geneva, September 4. It is a sympton of the present condition of atomic energy as an industry - not a sensation - that a piece of pure physics in no way related either to fission or fusion should have stolen the show at the atomic conference here to-day. Most people here appear to be glad that the excite ment of twelve years is now tapering off, so that they can throw their hats in the air (or even dance in the corridors as one distinguished American professor was reported to have done) at the news that the first ex periment to have been completed with the recently commissioned cyclotron at CERN (The European Centre for Nuclear Research) should have plugged one of the holes through which the spirit of fundamental physics has been leaking away in the last few years. British taxpayers can also be glad for they contribute something like a quarter of the annual budget of this cooperative research centre.

The simplicity of the fact which the cyclotron has demonstrated belies its importance. Briefly what the machine has done is to show that occasionally an atomic particle called a "Pi meson" decays as if it were a radio-active atom into a neutron. In their experiments the team at CERN has seen this happen on 42 occasions in a series of measurements of the decay of more than a million mesons. OCR Output

5592 GERN/285 Annex C — 5

The point is that this mode of radi0-&ctive decay is an alternative to a much more familiar one which has been recognised since 1947 as a result cf cosmic ray measurements carried out at Bristol. In this ordinary transformation, Pi mesons decay first into other part icles, called "Mu mesons", these in their turn decay into electrons. Until now no other method of decay has been discovered experimentally.

éP3;¥ ZLE .. This has been a puzzle because according to the most simple ideas of the relationship between light atomic particles the decay which turns a Pi meson directly into an electron would be the natural thing. Indeed the r6le which the Mu meson. has played in this relation ship has been obscure to say the least of it, and it is not an over—exaggeration to say that sound theoretical ideas would suggest that the Mu meson should not exist at all. Certainly for several years physicists have been driven to varied artificial explanations of its presence in the scheme of things. One way out ef this difficulty was, however, suggested some years ago by Fermi. He argued that it would be as well to regard the Mu meson as a kind of electron whose properties were similar in most respects to those of an ordinary electron, the only significant difference being that the mass of the Mu meson would be some 2lO times as great as that of the electron. According to this view direct decay into electrons should happen, but infrequent ly. Indeed roughly one in every ten thousand Pi mesons should be transformed directly into electrons. Unfortunately for the immediate success of this hypothesis, no direct decays were known and none were seen in experiments designed so as to find out. That is none were seen until a few weeks ago. In the CERN experiment the cyclotron has been used to make a stream of fast moving (and positively electrically charged) Pi mesons which were stopped in a block of material in circumstances in which the products of decay ceuld be accurately studied. The experiment has been so elegantly designed that it has been possible to distin guish between the two different modes of decay with high accuracy (mainly because the energies of electrons which result from direct and indirect decay are different).

5592 OCR Output CERN/285 Annex C · 4

g§Q§§NATIONAL TEAM "Professor Bernardini, who announced this news to-day, made a great point of saying that his team was inter national in origin. It includes A. Fazzini (Italy), A. Merrison (United Kingdom), W. Paul (Austria) and i. roiiestrup (USA). The significance of this step is hard to assess in practical terms. It will, for example, reinforce the tendency of physicists to regard electrons and Mu mesons as different states of the same natural entity, which will leave them with a new problem — to explain how nature arranges that the sane thing can exist in two different ways. It will stimulate still further the great interest which has recently been shown in the interaction between very light atomic particles, and it is also a crucial experiment in the strengthening of the chain of ideas which has been set off by the discovery two years ago by Lee and Yang for which these American physicists have been awarded a Nobel Prize. In the words of Professor Abdus Salam (of Imperial College), who has been almost dancing at the news, "a great mental block has been lifted and the new will be received with joy throughout the world." He described previous failures to discover direct decays of Pi mesons into electrons "as one of the most mysterious things in pnysics. He also said that according to his information, an American group from Columbia University had recently begun to accumulate evidence of direct decay, but that this team did not consider the number of events they had observed (four) to constitute a proof of the fact which CERN has now established.'

CORRIERE DELLA SERA - MILANO, September 6th, l958

"OGNI SEGMETEZZA ABBAUDONATA NEGLI STUDI SULLA FUSIONE NUCLEARE“

L'ambitissimo obiettivo e tuttavia anoora molto lontano

GINQVRA 5 settembre, notte. "Sono stati distribuiti oggi alla conferenza dell'atomo per la pace ben 296 documenti, 90 dei quali letti da novanta oratori nel corso di dieci riunioni 2 si tratta d'una giornata tra le piu quiete della conferenza. Oggi comunque OCR Output

5592 CERN/285 Amnex`C ` — 5

la ccnfercnzu é stata colta all'impr0vvis0 da una comuni cazionc chu l’0rdimc del giorno non pxcvcdeva, fatta dal prof. Bernardini, che dirige le riccrchc scientifichc del CERN il Centro europco per le riccrchc nuclcmri, al mmntcnimcnto del qumle a Gincvra partccipanc dodici Pacsi, frm 1 quali l'It&li&. Il CERN é per cosi dire il laboratcrio nuclcare della Europa 2 l’Eur0pa unite fe qual che fanno da soli gli Stati Umiti c l'U.R.S.S. 2 unendo i propri mczzi 1 d0d1c1 Passi sono r1usc1t1 u metterc in cantierc due fcndamcntali strumcmti d1 ricercu, un protosincrociclotrone G un s1ncr0— ciclotrcne. L'ult1m0 é gié prcnto 0 funziona da qualche mcse z gli scienzieti che leverane el CERN, impressioneti delle spesa che le ccstruzicne delle strumentc he ccmpcrtatc, erenc ensicsi d1 giungere el piu prestc e quelche risultetc, che giustificasse stehziamehti d1 fcndi ccs1 vistcsi. E 1l rieultetc e state cttenutc. Il pref. Bernerdihi he ehhuncietc che une squedra d1 studicsi, d1 gicvani f1s1c1 di vari Peesi che el CERN levcrahc cen bcrse d1 studio, he per le prime vclte, ccn ecper1cnzc di lebcretcric, ccnfermetc une fcndementele legge fisica enunciete in tecrie perecchi enhi fe, me mei compro vete cen l'esper1enze. La legge dichiereve che certe perti celle chiemete meschi p—grecc pctevehc decedere e sc1nders1 1h due mehierc, une delle queli ere rispettc ell'altra essei cesuele e rare. Il pref. Ameldi, prcs1dchte del Ccnsiglic direttivc del CERN, he spiegetc cggi ei gicrnelisti che s1 tretteve d'unc dei levcri cleseici 1n sede tecrice in fisice nucleere, e che l'esper1enze che cre lc cehferme e d1 grande impcrtehze per le scienze, pcrche de fiducia ei ricercetcri in certi pr1nc1p1, di cu1 bucne parte era state accettata senza la riprcve pratica d1 labcratcric. ll gruppc dei gicvani sciehziati giuhti a cesi lusin ghieri rieultati e ccetituitc dei fisici ital1ahi.Tit0 Eazzihi di Firenze, Giuseppe Fidecarc di Rcme, dell'inglese Rerriscn, dell'austriacc Peul et dell'americanc Tcllcstrup, he bcmbardatc per sei mesi, nel sincrcciclctrcne appena entrctc ih funzicne, del berillic, cttehehdc appuhtc dei mescni p—grecc : la decadenza dei mescni, che evviene in circa due centesimi di milicnesimc di secchdc, ha rilcvatc che elmenc quaranta vclte su circa duecehtc milichi di eventi eesi si scihdevahc direttamente in uh hcutrme e in un elet— treme, cenfermehde la teerie chunciate circa Venti anni fe. L'avvenimente ha grande impertanza in sede tecrica 2 in sede pretica - queste ccnferenza si eccupa delle epplicczieni pacifiche della scienza nucleere - ncn eene ancera visibili le sue censeguenze. In linea generale si pue dire che cenferma nei ricercateri la fiducia nei principi che li henne guidati in questi anni.

5592 OCR Output GERN/285 Annex C — 6

THB LONDON "TIMES" — September 5th, 1958 From our Science Ccrrcspcndent - GEHLVA, Sept. 4.

“Intcrnaticn&l scicncc, pursued for its own sake, stole thc limelight yesterday from the reactors end thermonuclear devices which are the mein subjects of the second United Nations conference on the peaceful uses of atomic energy. At cn informal afternoon session, five young physicists, two from Itely and one each from Britain, Austria and the United States, reported that they had completed the first substantial experiment with the first of CERN‘s big machines for the acceleration of nuclear particles to high energies, and in doing so hed resolved e difficulty which hed been e worry to physicists during the pest l0 years. The five physicists were T. Fezzini, G. Fidecero, A.W. Morrison, H. Paul and A. Tollestrup, members of the proton synohrotron division of CERN under Professor G. Bernerdini. The difficulty which they hed resolved was e point of behaviour on the pert of the unstable nuclear particle, known es the n -meson. The pi-meson, with 2 mess ebout 275 times that of the electron, is one of about 16 fundamental particles known to science, and the significance of the discovery, according to Professor A. Salam, of the Imperial College of Science and Technology, London, is that "a great mental block is lifted from thinking on the subject". It is the first major contribution to research from the lO-nation laboratory which is CERN.

££QTlCLE BREAKDOWN The 7T—meson is an unstable particle which in the normal way breaks down into a lighter, but still unstable, particle, the _u-meson which breaks down in turn to an electron. The difficulty has been that, to satisfy theoretical physicists, one in about every l0.000 VT-mosons should break down direct ly into an electron. Not only had this manner of breaking down net been observed, but experiments had been carried out which were taken to show that it did not happen. Because of the CERN experiments, 42 cases of this direct type of break down have been observed. The proportion is about one in 20.000, but it is thought that there may have been some more cases which were missed because of the difficulty of the exoeriment.

The direct and indirect modes of breakdown were distin guished finally according to whether two dashes, one for the pi—neson and the electron in the first case, and an extra one for the mu-meson in the second, were omitted from a scintillation counter. A second criterion was provided by the

5592 OCR Output CERN/285 Annex C - 7

energy of the final electron. Electrons resulting from thc indirect modo of breakdown have an energy of not more than about 55 million electron volts, while those formed by the direct route heve on energy some 15 million electron volts greater.

RIDDLE OF PHYSICS

The previous ebsence of this direct manner of broekdown hed, said Professor Salem, been described by Professor Peuli es "one of the greet mysteries of physics." The feet that it did occur would give confidence in the theoretical approaches new used in tackling problems connected with the fundenentel perticles of nature. In o general session on plens for the construction of nuclear power plants, Mr. Corbin Allerdyce, of the Inter national Bank, geve in general terms the results of a joint investigation with the Italian Government into the cost of electricity generation expected to result from the construc tion of a nuclear power station in southern Italy on the basis of nine tenders, compared with that from a modern oil fired station in the same conditions."

THE NEW YORK ·I‘ImES

KEY ATOMIC LINK REPORTED FOUND"

by John hillaby - GENEVA, September 4.

"A group of physicists announced today that they had discovered one of the missing links in the forces that hold the atom together. It was said to be of great impor tance.

Dr. Richard Feynman of the California Institute of Technology, who had taken no part in the discovery, appear ed jubilant. The discovery aided his own work by ironing out an anomaly in fundamental physics that had been worrying him for years. Dr. Feynman broke away from a food queue and danced a jig when he heard the news. The discovery relates to the decay or transformation of particles called pi—mesons thrown out when the hard cores of atoms are chipped or smashed inside big accelerating machines. The announcement was made informally at the Second Inter national Conference on the Peaceful Uses of Atomic Energy here by Dr. Gilberto Bernardini of Italy, who is in charge of the synchro-cycletron division of the European Council

5572 OCR Output CERN/285 Annex C - 8

for Nuclear Research. Headquarters of this joint European research project into fundamental physics is in Meyrin, near Geneva. Physicists there have one large (6oo MeV) synchro accelerator and seem to have hit a scientific jackpot on their first run. They are how building a much bigger machine. The discovery was made by five physicists, Tito Fazzini and Giuseppe Fidecaro of Italy, Alexander W. Morrison of Britain, Helmut Paul of Austria and Alvin Tollestrup of the California Institute of Technology. They were led by Dr. bernardini.

Dr. Bernardini explained that the problem that had worried physicists for twenty-three years was why sub microscopic bits of matter, called pi-mosons, did not directly decay into electrons, the particles that encircle the heart of the core of the atom the way satellites en circle a planet. According to a theory first postulated by the Japanese physicist Yukawa in 1925, the nucleus, or core of the atom, is composed of bits of tightly packed matter called protons and neutrons held together by nesons, which function as glue. They escillate as an exchange force uniting the neutrons and positively charged protons, otherwise the atomic core would fly apart.

léggrticles Known to Exist w There are now known to be about sixteen fundamental particles and the mesons or pi-nesons not only bind the atomic core together but have a mass intermediate in weight between the atomic core and its encircling electrons.

For this reason it was assumed that when an atomic force was chipped or smashed in an accelerating machine (or by the force of cosmic rays) the pi-mesons would be released and in fraction of a second they would decay into electrons. This, at least, was what Yukawa predicted. But it was found that instead they decayed into an intermediate part icle called a mu-meson and then into an electron. The existence of the mu-meson could be explained in terns of the complicated equations of fundamental physics, but by all known laws of matter there was no reason why researchers should not occasionally find a pi-meson that decayed direct ly into an electron. But until recently they never found one. OCR Output

5592 cmm/285 Annex C — 9

But the anomaly seems to have been rqctificd. The physicists in Meyrin induced protons into their sccolorstor ond whirled them around a track by moans of oloctromognets until they approached thc spocd of light. Tho protons wars thon hurled against a target of carbon, where the pi-masons promptly escaped by means of thc cnergy of the collision. Some plunged through a linkod—battcry of particle counters where the physicists were able to detect what happened to them. During the split—second decay period they were delighted to get two blips, or pulses, instead of the normal three. The two indicated that a meson had become an electron without providing the extra blip of the mu—meson stage. This was Yukawa's theory in action. The experiment was repeated again and again and the direct decay was found to occur about once in l0,000 times. This is approximately the relationship needed to regularizc the mechanics of the decay theory. It ties with the theory of the distribution of forces inside the atom.

Reservations Voiced Here Reservations were expressed here yesterday by a Columbia University physicist concerning the discovery announced at Geneva. Prof. Jack Stcinberger, who heads a team of physicists working at Columbia on the same field of research in pi mesons, said that work done by Prof. Herbert Anderson, director of the Enrico Fermi Institute of Nuclear Studies at the University of Chicago, had produced the opposite results from those indicated in the Geneva announcement. Physicists now are consequently left with a contradiction, he remarked". "

5592 OCR Output GERN/285 Annex D

CERN Press Release — September, llth, 1958

QRpQIgILg§PERIMENT NITE CERN 600 MeV §j§Q§§pg£QQIQTRON

The CERN 600 MeV synchro—cyclotrcn has just made its first major contribution to nuclear physics. The two high energy machines at CERN, one of which is still under construction, have been built specifically to study the properties and interactions of so—called elementary particles. One of these particles, the 7T»meson, was disc vered in the cosmic radiation, about ll years age. It was observedgthen that it decayed, in a very short time (about I0- seconds), into a ;4—meson. The éyemeson itself decays in a rather longer time (about l0- seconds) into an electron.

Not long after the discovery of the 7T=meson, it was predicted on very simple and straightforward theoretical grounds that every so often the 7T—MOSOH should decay, not into a ji—meson but directly into an electron, and that this should occur once in every ten thousand decays (I in l0 ). Experiments were performed at the Universities of Columbia and Chicago to look for these rare decays with the result that the process was not observed, and that if it occurred at al%, it must be less than one in one hundred thousand (l in l0 ). The discovery, two years ago, that parity was not conserved in certain processes in nuclear physics, produced a very great simplification of our understanding of these phenomena. But there were still one or two major difficul ties left, and one of the most serious of these was the negative result concerning the electron decay of the pion. This inspired several groups of physicists throughout the world to search once more for the process, and one of these groups, at CERN, has been successful. They have demxnstrated that this decay does occur, possibly with about the expected frequency. This has certainly eliminated a crucial difficulty for the theorists. The group responsible for this experiment at CERN illustrates very well the essentially international character of the CERN laboratory. The group was made up of T, Eazzini (Italy), G. Fidccaro (Italy), n.W; Morrison (ur.), H. mai (austria) and Ay. rciiestmp (esl,). Head of Research of the Synchreeoyclotron Division is Professor G. rernardini (Italy). Director of the Division is Professor W. Centner (German Federal Republic).

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