Recollections and reflections about Bruno Pontecorvo

S.S. Gershtein

Now, when I am writing these recollections, I can clearly see Bruno Maximovich arising in front of me, quite alive, with his invariable smile, humour, interest in people, craving for knowledge, his tact and profound democratism, owing to which he could speak identically to persons of the highest positions and to workers in the workshop, with his intoloerance of any falsity and especially of ignorance in science, his readiness to give all support to new interesting experimental investigations.
Bruno Maximovich belonged to that remarkable stratum of physicists, whose works happened to form the foundation of modern nuclear physcs, nuclear energetics and technology, elementary particle physics.
It is well known that precisely the experiments carried out by young Pontecorvo together with Amaldi in Fermi's group served as a stimulus for the discovery of the slowing down of neutrons - the effect which underlies the operation of modern nuclear reactors, the production of many important isotopes, and which has played (and still plays) an important part in research in physics.
It was precisely Pontecorvo who in 1946, when the first information on the relatively long lifetime of muons in matter was obtained, put forward the hypothesis of the universal character of weak interactions, of a new force in Nature, the only manifestation of which was hitherto represented by radiactive b-decay. Precisely Bruno happened to be the father of experimental neutrino physics, having raised in 1946 the issue of the possible registration of neutrino from nuclear reactors and having elaborated for this purpose the radiochemical (in particular, the so-called chlorine-argon) method for detecting nuclear reactions induced by neutrinos.
In his famous report of the Chalk River laboratory in Canada, Bruno prophetically touched upon other aspects of neutrino physics by mentioning the Sun and accelerators as possible sources of neutrinos. I believe these ideas of Bruno reflected his human qualities - his incredible scientific courage and broad views. At that time actually nobody thought it possible to implement such experiments. Even E. Fermi, as Bruno recalled, treated the idea of neutrino registration with considerable apprehension, and was much more interested in the technology of proportional counters, developed by Pontecorvo and applied by him in a number of studies ("Don Quixote was not Fermi's hero", - Bruno noted, in this connection).
Bruno's ideas and calculations served as a stimulus for experiments. When the technique of large scintillators (which did not exist in 1946) had been developed, straightforward detection of neutrinos turned out to be possible, and was realized by Raines and Cowen in 1953 - 56. The chlorine-argon method was subsequently developed by Davis. With its aid, it was first established that reactor antineutrinos differ from the neutrinos, and neutrinos from the Sun were detected.
At the time, when Bruno put forward his proposal for the detection of neutrinos, it was not known that the chain of thermo-nuclear reactions taking part in the Sun could (although with a small probability) result in the production of Be and B nuclei, which are sources of neutrinos of quite significant energies capable of inducing the chlorine-argon reaction: +37Cl37Ar+e-. Precisely such neutrinos were detected by Davis with the aid of the chlorine-argon method developed by Bruno. As to the main flux of solar neutrinos originating from the fusion of two protons into deuterium accompanied by the emission of a positron and neutrino, Bruno did not envisage in 1964 the possibility of their detection, owing to their energy being too small. It turned out, however, that the radiochemical method proposed by him was suitable for this purpose, also .
At present, the results of experiments aimed at detecting solar neutrinos draw the attention of physicists from all over the World. This is related to one more brilliant idea of Pontecorvo. In 1957 he pointed to the possibility of one sort of neutrinos undergoing, in vacuum, transformation into another sort, i.e. to the possibility of so-called neutrino oscillations. It turned out to be that such a possibility is closely related to the Grand Unification of various interactions at super-high energies. Searches of neutrino oscillations have already been under way for many years in various laboratories throughout the World at reactors, accelerators, meson factories, thus forming a significant part of research programs. However, as indicated by Pontecorvo, only solar neutrinos (owing to the enormous distance from the source, as compared to Earth scales), provide the possibility of extending investigations to the region of small neutrino masses totally out of the reach of experiments on the Earth. Precisely such neutrino masses are to be expected on the basis of Grand Unification models. Therefore, when the first experiments in which solar neutrinos were detected yielded a 2-3-fold decrease of their flux, as compared with calculations, Pontecorvo was the first to voice the idea that this fact might be related precisely to neutrino oscillations transforming electron neutrinos into other, "sterile", states not capable of inducing nuclear reactions.
Now, after the remarkable work of S. Mikheev and A. Smirnov, who showed that taking into account the coherent scattering of neutrinos in matter (considered by L. Wolfenstein) can significantly enhance neutrino oscillations in the case of small differences between their masses and of small mixing (and can even result in all neutrinos undergoing transition into "sterile" states), B.M. Pontecorvo's idea yields the most plausible explanation of the results of the Gallium, Chlorine-Argon and electronic (Kamiokande) experiments for detecting solar neutrinos.
The gigantic experiments under preparation in several laboratories around the World will permit testing this possibility reliably in the near future. Thus, Bruno's ideas are paving the way toward the physics of the next century, making it possible to obtain information on the Grand Unification of the forces of Nature. This is not the only example of how the ideas and experiments of Bruno served as the starting point for experiments being carried out for decades with constantly increasing accuracy. Such, for instance, are the searches of the µe decay and the determination of the electron neutrino mass from the spectrum of the -decay of tritium, initiated by Pontecorvo nearly half a century ago. I shall not mention other brilliant investigations carried out by Pontecorvo. I only wish to stress the importance of the work done by Pontecorvo for the physics of the XX and XXI centuries.

Bruno arrived in the Soviet Union, when he was 37 years old and he was in the prime of his life. During his life in the USSR he performed a series of brilliant investigations, including high-precision experiments on the scattering of -mesons on nucleons, on parity non-conservation in the µ-decay, on the capture of muons in He, on tests of the hypothesis of pair production of strange particles in nucleon-nucleon collisions, which he incidentally put forward before the appearance of the Gell-Mann-Nishijima scheme, and many others. Here, he put forward his famous hypothesis on the possibility of neutrino oscillations and on the role of detecting solar neutrinos for their revelation, he pointed out the possibility of performing neutrino studies at acclelerators (for instance, for resolving the problem whether the muon neutrino is identical to the electron neutrino, or not). Pontecorvo exerted an invaluable influence on the level of studies in elementary particle physics in our country, having established very high criteria, which had to be satisfied in some way or another, he educated a large school of experimental physicists and stimulated many theoretical investigations. Many important new experiments were actually performed only owing to the active support rendered them by Pontecorvo. Bruno Maximovich participated actively in establishing the Institute of high energy physics and in elaborating its research program. For many years he was Chairman of the neutrino Council at the USSR Academy of Sciences and gave invaluable support to many experimental studies. In recent years he was especially enthusiastic about the research program in neutrino astrophysics being implemented by A.E. Chudakov and G.T. Zatsepin. Together with A.M. Markov he did everything to support it at all levels.

Regretfully, Bruno could not realize his own bold ideas:
  • to detect antineutrinos from reactors (which was done by F. Raines and K. Cowen in 53 - 56 and for which Raines received the Nobel Prize in 1995);
  • to demonstrate the muon and electron neutrinos not to be not (for which L. Lederman, J. Steinberger and M. Schwartz received the Nobel Prize).
Why that happened is quite evident, the answer to this question lies fully in the conditions of life and scientific work in the Soviet Union of those times. As to the problem of two neutrinos, it could not be resolved in the USSR because of the absence of an appropriate accelerator, while the issue of making Pontecorvo's proposal the basis of some international experiment at CERN or in the USA involving his participation could not even be thought of, given the conditions of those times. (More so, considering that even two decades later Bruno was not granted permission to go outside the Socialist Commonwealth, under the false pretext of his safety).

The situation with the detection of reactor antineutrinos was even more offensive. I learned about it just by chance. In 1956, when I was a post-graduate student of L.D.Landau at the Institute of physics problems, one of the leading experimenters of the institute - V.P. Peshkov - instructed Medvedev, one of his post-graduate students, to think about how to implement an experiment for detecting reactor antineutrinos. V.P. Peshkov himself was a refined experimental physicist in the field of low temperatures (thus, for example, he was the first to reveal the second sound in superfluid helium), and, moreover, he was also a big shot in the State committee for science and technology besides having access to operating reactors. Knowing that I was interested in weak interactions Medvedev contacted me, and we started thinking about the experiment together. By that time the presence of Pontecorvo in the USSR had already been made public, so when Bruno come to the Physproblems , we asked him to take part in a discussion of the feasibility of such an experiment. He readily agreed. From the discussions with him we understood how naive we had been to think it possible to carry out such an experiment exerting relatively little effort. Bruno gave some useful advice, especially concerning the background. I remember that he recommended putting the detector under the reactor, which would thus serve as a certain protection against cosmic rays. At the end of our conversation we asked him why he himself didn't make this experiment. At the beginning Bruno avoided answering. But, when during the discussion we once more asked him the same question, he reluctantly (with embarassment, it seems to me) answered that he was not granted access to any reactor. I was astonished at the time. Without doubt, if investigations had started in 1950, when many industrial reactors were already operating and new ones were under construction, Pontecorvo, with his knowledge and skill, could have been the first to detect neutrinos (moreover, new detection methods had appeared, which were unknown in 1946). This high fence set up by the authorities could not even be overcome by I.V. Kurchatov, who was very interested in the work of Pontecorvo. Thus, for example, he provided Bruno with a sufficient amount of 3He for an experimental study of µ-capture, and V.P.Peshkov helped Bruno to clean the 3He thoroughly from tritium, the presence of which made it impossible to perform the experiment with a diffusion cloud chamber.
The origin of the presented 3He was evident. It was "waste" from the production of tritium (the material for a hydrogen bomb), so the amount of helium used was declared secret, and it was forbidden to make it public, when the results were published, although a competent physicist could easily calculate it knowing the experimental device and the conditions of the experiment.

To everybody who knew Bruno it was obvious that he could have achieved much more working in the West and could have realized his own ideas himself. In this connection, many people asked the question: "Why (or for what reason) had he come to the USSR?" Some were of the opinion that it was done because of the naive belief of many foreigners, faithful to the idea of communism, that the USSR being the country of victorious socialism was building a communist society. When it became more of less safe to discuss such issues, some people cynically called it "stupidity". Others, espicially malevolent to Bruno (there were such people, even though a small number), adhered to the version adopted then in America: he was a Soviet spy who fled when the danger arose of his being unmasked.

Although we were friends with Bruno for many years, I, personally, never asked him this question, since I understood that it might be quite painful for him. But the numerous discussions we had with Bruno led to a certain opinion forming in connection with this issue. I shall give some examples. Once at the JINR Scientific Council I happened to sit together with Bruno on the back-benches. A talk was presented by Fuks, a former well-known Soviet spy, who, after having served his term in prison in England had gone to GDR and worked in Dresden. His talk did not seem very interesting to me (something about the Young schemes). Bruno, however, was very excited. One could see that this encounter made a strong impression on him and was somehow connected with his own life. "You know, - whispered Bruno to me, - Fermi was very severe in estimating scientists. But he considered Fuks a star of the first order". I thought Bruno would go to speak to Fuks at the end of the session, but he didn't do so, and we left the Scientist's Club together. Bruno was agitated. Most likely, he was recalling past years, just before he came (or, one can say, fled) to the USSR. "I would be very interested in reading the memoirs of Fuks, if he wrote any, - said Bruno. - The point is that when Fuks was arrested, we were all sure it was a Police provocation against the communists, since we learned that Fuks was a communist. We had no idea Fuks was a spy, and we thought it was a provocation in the spirit of McCarthyism, which had overflowed America and had extended to England".

From these words of Bruno it becomes quite clear what he, a communist since 1936, could be afraid of in England after the arrest of Fucks and why he decided to change his life so drastically.
It could also be possible that the prospect of working in Dubna at the then largest accelerator in the world played a significant part in his taking the decision to go to the USSR. The construction of this accelerator was a secret at the time, but the secret services that organized Pontecorvo's journey to the USSR, could have told him about it, or at least hinted.
Bruno told me he joined the underground Italian communist party in 1936 at the time of the war in Spain. Being a democrat and an intelligent young person living in a fascist country, he hated the fascist regime, and the war in Spain threatened to spread it. The communists then seemed to many the most decisive opponents of fascism. And this fact served to make many very worthy people thoughout the world come very close to them - both in Europe and in America .
After he joined the communist party, Bruno took the communist ideology for a true science and faithfully followed it until life in the USSR gradually destroyed his illusions one by one. It was a very painful spiritual process for him. Already after the "perestroika", I don't remember exactly when, in 1991 or 1992, at a general session of the Academy of sciences, Bruno sat down beside me and said: "I am writing my autobiography for an Italian publisher. I have done a lot of thinking. Nearly all my life I considered communism a science, but I now see it is not a science, but a religion. I thought Sakharov a very good, but naive person, and now I see it was I who was naive."
Bruno's definition of communism as a religion was a very good point. It explains much in the behaviour and fate of many faithful communists in the USSR and abroad. Most faithful western communists, who were the most ardent believers loyal to the USSR, doubtlessly were advocates of communism "with a human face", and thought they were struggling for the happiness of mankind. But, since the principal dogma of "scientific" communism, unlike "Utopian" communism, was that this goal can be achieved only with the aid of the dictatorship of the proletariat, they were compelled to justify the suppression of freedom in the USSR before other people and before themselves by assuming it to be a temporary phenomenon related to the transition period and absolutely not apprehending the scale of the atrocities and crimes taking place, not understanding that it was not a dictatorship of the proletariat that existed in the USSR, but a dictatorship of the criminal party bosses (religion permits no doubt). I remember how at the time of the XXII CPUS congress, when further (far from complete) unveiling of the cult of Stalin took place, one physicist from Dubna, who was not content of this, cruelly asked Bruno the question: "Was it possible for the foreign communists to know nothing about all this before?". "Yes, - answered Bruno, - in the 37-s all the bourgeois newspapers wrote about it continually, but we thought it to be lies. And those communists who believed the newspapers finished badly - they went over to the fascists". At the time, when animated discussions on the personality cult of Stalin took place, Bruno tried to not to give way unconditionally to the general mood and to retain objectivity. Thus, he justified the conclusion of the Soviet-German pact of 1939 (we could just guess of its secret Appendices from the division of Poland and the annexation of the Baltic states that happened immediately). "You didn't live abroad and don't realize, - said Bruno, - how all the bourgeois newspapers wrote that it was necessary to incite Hitler and Stalin to hostilities between each other, so they would destroy each other". When, after one argument we remained alone with Bruno, he added: "Truly, Stalin shouldn't have sent a telegram of congratulation to Hitler after the division of Poland. That telegram surprised us, communists, very much and sowed doubt in our minds".
Bruno then also thought that the repressions of the 37-s resulted from internal political struggle in the party. I had to tell him much about various facts of our history: about the horrors of collectivization, of the famine in Ukraine (I had heard about it from witnesses), about the Lenigrad lawsuit, the lawsuit against the doctors, about the tragic fate of the Alliluyev family and of my own, and about many, many other things. Bruno trusted my stories, because, being the son of parents having experienced repression and not being a party member, I nevertheless for some short time shared, like many others, the illusion that the Lenin norms of life were to be restored and of the possibility of creating socialism with a human face, not understanding that Stalin was actually a product of Lenin's doctrine. The beginning of the end to these illusions was the defeat of the local party organization of the ITEP in 1956 (nearly immediately after the XX Congress) and the fate of Yu.Orlov, who always was, and still remains, one of the most intelligent, honest and courageous persons I ever met in my life. We also discussed this matter with Bruno, but a clear comprehension of what was happening came only later.
When I first visited Italy in 1989, I met a young physicist from the university of Rome. He told me that when he was a student he believed in communism and worshipped the USSR. "Luckily, - he said, - my father, who was a pharmacist, prescribed me a good medicine. He bought me a tourist ticket to the USSR, and so I was cured. In my case, - he added, - the healing started already at the Moscow airport". Regretfully, neither Bruno nor thousands of other believers had the opportunity of taking such medicine.
In this connection, I want to tell the story of an outstanding person, an Italian communist, the name of whom is known to few in our country (with the exception of old aviation specialists) whose fate, even more tragic than Bruno's, made Bruno suffer significantly. I am speaking of Roberto Oros di Bartini. In 1962, N.N. Bogolubov, then LTP director, summoned me and asked me to study an article rejected by the JETP with a review containing very offensive comments. "This work, - said N.N., - was given me by M.V. Keldysh, who knows the author well from joint work in aviation and cosmic industry. He asked me to see, whether it could somehow be published upon introduction of some corrections. The author had experienced a difficult life. As a young person he had come to the Soviet Union, had numerous merits in aviation, in the 30-ies he was sent to prison, and at present he is working actively again. Please, look at this article. Maybe it can be corrected and it can somehow be published in the newly founded journal Yadernaya Fisica (Nuclear Physics). If difficulties arise, I shall personally present it for publication in the "Doklady AN".
I started to study the article full of concern for the author. The article began thus: "Consider a total and therefore unique specimen A". Only after considerable efforts was I able to understand that the author intended specimen A to be the entire Universe. Indeed, it is unique. Further, the author assumes it possible for specimen A to be realized in space-time of several dimensions (not necessarily four) and for there being a certain probability that transition occurs from one number of dimensions to another. At present, when a renaissance has taken place of theories such as the Calutsa-Klein theory and spaces of quite a large number of dimensions are considered involving their compactification, such a hypothesis could well be accepted. But everything was happening at the beginning of the 60-ies, and it certainly seemed absolutely wild to referees. Nevertheless, I thought the author to have the right to adopt this hypothesis (I was influenced by my sympathy for him). Further developing the hypothesis, the author arrived at the conclusion that the most probable space for the Universe should have 6 dimensions, and on the basis of "geometrical" arguments he derived a number close to the doubled fine-structure constant 1/137. Then, by correcting this number in accordance with experimental data and taking the Bohr radius as a standard, the author calculated the Compton length and the classical radius of the electron to be in "astonishing" agreement with experiments. This, naturally, was just nonsense, since it is known that these quantities represent, by definition, the Bohr radius multiplied by the first and the second power of the fine-structure constant, respectively. The article even contained a certain expression for the gravitational constant, which could be considered empirical.
It was quite clear to me, that no physics journal would accept this article both because of its physics content and because of the language in which it was written. I decided to change the text by rewriting it so as to render the author's assertion comprehensible and to discard the "agreement" with experimental data, which was based on the definitions of quantities. Upon having prepared an "abridged" text I rang up the author to discuss it with him. Bartini invited me to his home on the Kutuzovsky prospekt. When I arrived, I saw a charming handsome person with surprisingly courteous and pleasant manners (Bruno told me afterwards that Bartini came from a distinguished aristocratic family, with whom he broke, in spite of his father, - a baron and former governer of Fiume, - who was devoted to him, being a person of quite broad and democratic views).
From the very beginning I understood that I was dealing with a person unusually gifted in all respects. There were remarkable paintings on the walls of the apartment, small sculptures were on the tables together with models of some fantastic aeroplanes. Everything, as I learned, was made by the master of the house. Bartini very gently expressed his disappointment with my text. He considered I had cut out many of his important ideas, and (in spite of my arguments that no journal would accept the article in such a form) fought literally for each word. In doing so he based his ideas on appropriate arguments from the book by Eddington and from other similar books. I was not able to convince him that they would not be accepted as reasonable arguments by the editors. Our debates often went beyond the article discussed and concerned philosophical issues (I was astonished by the knowledge of the author in ancient, classical and marxist philosophy). Thus we passed several evenings in hard work.
As I understood, Bartini worked in Podlipki in the well-known secret designing bureau. But at the moment he only considered the work we discussed to be the main goal of his life, and he was in despair because he could not get it published. "My "trade" (he thus called his work in the designing bureau) is quite successful, but the main thing is the work we are now discussing" - he said. In breaks between discussions, when we drank tea at the desk, I tried to direct our conversation toward Bartini's work in prison. I had heard something about it from Yu.B.Roumer. Bartini spoke quite willingly: "We had three departments: Tupolev's, mine and Roumer's. Roumer dealt with dynamics, i.e. flutter, and we were friends (so this was the origin of Bartini's interest in the multidimensional Universe, I thought). There were many well-known people working in my department, such as, for instance, Korolyov. The future rector of TSAGI worked as a draughtsman".
I don't remember, now, whether Bartini himself told me about one interesting episode of his life, or whether I heard it from Bruno. The point was that Beria himself often came to visit the "sharashka", he used to summon the Heads of departments for discussing work and new assignments during tea-breaks. Once, seeing the benevolent attitude of Beria, prisoner Bartini turned to him to say: "You know, Lavrentii Pavlovich, that I am totally innocent". "Of course I do, - answered Beria with a strong Georgian accent, - if you were guilty, you would have been shot. Okay, you'll make an aeroplane, receive the Stalin prize of first order and be set free". Baritini, who in spite of everything had retained his naivety, was perplexed: he couldn't understand the relationship between an aeroplane and the horrible accusations of espionage and other sins, for which he had been convicted. Had he been free, he would have worked faster and better on the construction of his machine.
When a more or less cut text of the article had been agreed upon and sent to Yadernaya Fisica, I asked Ya.A. Smorodinsky to send it to me to be reviewed. I wrote a quite objective review, pointed out the admissibility of the hypotheses put forward (in spite of their being unusual) and recommended publication of the article. At the same time I asked Ya.A. to send the decision of the editor to me, in case the article was rejected, because I was afraid Bertini might not recover from the rejection of his article, and I remembered N.N. Bogolubov's promise to present the article for publication. When, in spite of my review, the editing board of Yadernaya Fisica rejected Bartini's article, I took it to Nikolai Nikolaevich. He reflected for a moment. "You see, if I present this article, there may be a scandal, since I am a theoretician. It would be better, if this were done by an experimenter, who may later say he is not a specialist. For instance, Bruno Maximovich has just been elected member of the Academy. He now has the right to present the article for publication in "DAN" himself".
I went to Bruno. "I wouldn't really like this article to be the first one I present, - he said, - but there's nothing do about it. Bartini has to be saved. Otherwise he'll lose his mind". So Bruno presented the article in a somewhat corrected form. (When it was published in DAN, Bruno was surpized that Bartini signed it with his full name, retaining the prefix "di"). Bruno was extremely concerned about the fate of Bartini. "He came to the Soviet Union a very young man. In Italy, even in the communist party, he is known to nobody; most likely he is remembered only by several old people, such as senator Terracini".
When the article was published, Bruno did experience some unpleasant moments. First, he immediately received letters from several "crazy" correspondents who accused him of presenting ideas stolen from them. Second, he received a telephone call from the Department of Science of the CPSU Central Committee inquiring whether the article was a joke or not. Precisely such a complaint was sent to this authoritative organ by certain mathematicians, who considered it an insult for a practical joke to be published in a journal, where they published their brilliant works. (That the article, starting from the first phrase presented above, was a joke gave rise to no doubts. They also thought the unusual name of the author to be a fabrication, which seemed to be an incomprehensible part of the joke). When speaking with the instructor of the Central Committee, Bruno (as he usually did when stopped by a policeman regulating traffic) began speaking in very broken Russian and indignantly repudiated the very suggestion of "Robert Oros di Bartini" being an imaginary person. "Go to the Defense Department of the Central Committee. They should know him there. It's very strange you don't", - he said. The debate finished there. Later on, I saw Bartini's work in the collection on gravity published by K.P. Stanyukovich.
Sometime in the middle of the 60-ies I saw an article about Bartini in the weekly "Nedelya". There I read that when presenting Bartini to the Council for science and technology S.P. Korolyov called him his teacher, and that the Italian communist party presented Bartini with a memorial medal. Bartini was awarded the Lenin orden. The pupils and close collaborators of Bartini, supported by the minister of the aviation industry, had decided to found a Bartini museum. By chance I happened to see the booklet by I. Chutko, "Beautiful aeroplanes", in which people who knew and loved Bartini tell the story of his life and work. I would like to quote the words of academician O.K. Antonov, Constructor General, from the preface to this book: "Roberto Bartini was a person of unbending beliefs, a person of the purest crystalline spirit, a passionate internationalist. ... His firm belief of a communist in the happy future of all mankind was the guiding star thoughout his life". Regretfully, in the quite good book by Ya. Golovanov about S.P. Korolyov only a few words are said about Bartini, although Korolyov worked in the his Department and subsequently considered Bartini his teacher. Evidently, the long-time habit of writing the half-truth had some influence here, also. It is quite clear that the image of S.P. Korolyov would not have tarnished, but on the contrary would have only gained, had the real position of Bartini in the "sharaga" been reflected together with the obvious gratitude to him felt subsequently by Sergei Pavlovich.
I beg the readers' pardon for devoting so much place to the history of R.Bartini in my memoirs of Pontecorvo. I did so, being quite sure Bruno would have approved.

It must be said that Bruno sincerely loved physics, and rejoiced at its achievements, whoseever they were. He could speak enthusiastically about other's experiments, admire some newly applied methods or some ingenious realization of an experiment. I remember how well he spoke of the experiments performed by Yu.D. Prokoshkin, P.E. Spivak, F.L. Shapiro, V.M. Lobashov and many others. He spoke with fascination about his collaborators, with whom he did experiments, noted their inventiveness and contribution to the success of the experiment, spoke very warmly about his joint work with the theoreticians L.B. Okun', V.N. Gribov, and others. I noticed Bruno particularly liked talented independent persons, who were known to be "unmanageable" and difficult to communicate with. He greatly appreciated original thinking (for example, he emphasized the originality of B.S. Neganov's reasoning). He could not be said not to note small defects and weaknesses, on the contrary, he saw them quite clearly and liked to make jokes about them. But Bruno was absolutely irreconcilable in his criticism, when he saw defects in experiments, the absence of test measurements, a "frivolous" attitude towards the mathematical processing of data, and, in particular, any cheating. In such cases he spoke out independent of the individual.
Such a stand of Bruno somtimes created new ill-wishers and even enemies. In this connection, the quarrel between Bruno and G.N. Flerov was especially painful to me. Having supported at a time S.M. Polikanov in his depute with G.N. Flerov concerning the insufficient reliability of a newly discovered element and having helped S.M. Polikanov in his transfer to the Laboratory of nuclear problems, Bruno incurred G.N. Flerov's hostility. G.N., regretfully, in the spirit of those times took advantage not only of scientific, but also of political, arguments. Bruno indignantly showed me the record in shorthand of the meeting on the case of S.M. Polikanov, who emigrated from the USSR. Bruno himself was absent at the time, so couldn't be at the meeting. The recorded attacks of G.N. against Bruno reminded speeches in the spirit of 1937. I regretted this hostility very much, since, in spite of many known defects and the absolutely unworthy behaviour of G.N. at that meeting (of which I told him), I liked Flerov for his unusual character, his talent and purposefulness (it may be that I was also influenced by his respect for me). I tried somehow to lessen the existing hostility, but without success.
Objectivity of valuation was a rigorous rule for Bruno. Happening to be in the midst of various competing groups and schools, Bruno never, as far as I know, violated this rule, independent of his scientific or personal sympathies. This also caused dissatisfaction among various parties. I remember how once Bruno complained to me that at some workshop on organizational issues K.A. Ter-Martirossyan called him a "compromiser". "He called me, member of a clandestine communist party since 1936, - said Bruno, - a collaborationist". I understood how this word, that had already been out of political use for a long time, could affect a communist since 1936, when the main task of the communist parties was defined as the struggle against "compromisers". This story, however, had no effect on the good relations between Bruno and Karen Avetovich, whom Bruno valued highly as a physicist and a very kind straightforward person, ready to fight anything unjust. "He is a noble Don Quixote, sometimes even capable of attacking wind-mills," - Bruno used to say.
Owing to his wanting to be objective, Bruno experienced particularly difficult times during elections to the Academy of sciences. He often sought advice and discussed the scientific merits of the different candidates. At the time I was quite far from the academic "cook-house", so I was surprised when just before one of the elections he said: "I would very much like X to be elected to the academy, he is my first candidate, but I cannot vote against Y, since Y is an excellent and original physicist". I answered that that seemed to me quite natural. "Yes, - said Bruno, - but when some people adhere to objective valuation, while others vote only for "their" people, you are bound to lose. Nevertheless, I cannot behave otherwise". Therefore, Bruno always tried to achieve a compromise. One of the means for doing so was the academic "game", an unofficial test vote held within the Department, which permits identifying the candidates most acceptable to the majority of the Department members and, then, to conclude an agreement between the various groups on their election. This made it possible, without dispersing votes, to achieve election of the candidates singled out in the official voting (which was limited by the rules to three rounds, otherwise the places allocated to the Department were lost). Naturally, this method could be successful only if the persons who voted in a certain way in the last decisive "game" didn't change their postions during the official voting. Thus, to be brief, the game had to be "gentlemanly". Once, Bruno quoted the words of I.M.Frank to me: "What a respectable Department we have. Everybody voted just like agreed". I was surprised by these words, not understanding how it could be otherwise. Later, however, it turned out to be quite possible. And Bruno was so shocked, that he seriously thought of transferring from the Department of nuclear physics to the Department of general physics (and even started negotiations). Luckily, he was persuaded not to do so. The position of Bruno during the voting was the following: he considered that if a group abolutely wanted to elect its candidate by blocking the election of other candidates, more worthy in the opinion of Bruno, it was necessary to reach an agreement that would let the most worthy candidates also be among the ones elected. However, bearing in mind the results of the preceding "game", that had shocked him, he once demanded, in a critical situation, that the voting be actually carried out publicly (with open ballots). This showed that Bruno was no longer so naive as before. There were people who condemned him for this. But life proved Pontecorvo to be right.
I remember Bruno to be an exceptionally versatile person. One of his hobbies was sport. As soon as he arrived in Dubna he started actively playing tennis (it was not yet in fashion). He would passionately speak of the tennis competitions of his youth and would be surprised I had not heard of the tennis stars of those times. It seems he was the first in our country to start underwater swimming, together with A.B. Migdal and his friends. (A.B. was one of his closest friends, but Bruno also liked his companions. He spoke with particular warmth about Suetin - a brilliant engineer, inventor and talented person). Once Bruno nearly caused a state of alert in the fleet stationed in the Black sea, when he came out of the water in a hydro-costume and mask (unseen at the time in our country), speaking with a foreign accent; he was taken by the border guards to be a spy set to shore by a submarine.
Bruno was an excellent cyclist. Once he demonstrated to me his fast riding with his back to the steering handle. He continued going on bicycle even when he was ill. In 1990 he fell from his bicycle and broke his thigh bone. Luckily, G. Piragino, scientific counsellor of the Italian embassy in Moscow, helped transport Bruno for an operation to Italy, where there was a doctor familiar with Bruno's illness and who knew which anesthetics could be applied in his case. It so happened that I went to Italy one week later and could take the opportunity to visit Bruno in the hospital in Rome after the operation. He was already getting better and was happy not to have his unhealthy tremor.
I think Bruno adored risk and adventures. Both in science and in everyday life. But, while in science his risk was always based on scientific arguments, in sport and travelling the risk often threatened his health and his very life. When we were once skiing down the slopes of Mt. Aragats in Armenia Bruno noted: "I used to do this much faster without thinking of possible precipices beyond the bend of the hill. But after I broke my legs several times I became more careful". Once a boat in which Bruno was going together with Dolgoshein and others (I think it happened near the Kuril islands) capsized several kilometres from the shore, and everybody had to swim back. Misfortunes sometimes seemed to happen to Bruno without any reason at all. Once he decided to go for a walk along the frozen Volga river togther with Marianne, whom he treated with touching attention and care, and fell through the ice till his shoulders, but was able to get out onto the ice. Some time later, when he was already ill, in the centre of Moscow a person, obviously some maniac, hit him so Bruno fell and hurt himself quite strongly. Such events always made us suffer.
Bruno was keen on cinema. To a great extent, this was due to his brother Gillo Pontecorvo, whom he was very fond of. After each cinema festival in Moscow, Bruno was overflowing with impressions and he told us not only about the films, but also about various funny situations, such as the following: a very well-known Italian star quite straightforwardly asked Yu.Gagarin, who was invited to the festival: "What do you think, is it possible to reach a star?" "No, - answered Gagarin, - the technology will not permit it". "Think a bit, might it not be actually possible?" "No", - stubbornly answered Gagarin, clearly understanding the hint.
Bruno was very happy when G. Pontecorvo succeeded in making a remarkable film "Capo". He told us of the problems that arose when the film was to be purchased and shown in the Soviet Union. Furtseva seemed to approve buying it. But some of the cinema magnates were against on the pretext that the one of the main characters - a Russian soldier - had a coarse face. "It doesn't at all seem coarse to me, - said Bruno when retelling the content of the film, - through this seeming coarseness one can clearly notice strength and intelligence". Bruno himself liked such people. Naturally, all such objections were just a pretext. The film was not bought.

Pontecorvo, naturally, felt homesick for Italy. But this nostalgia was hidden very deep and only rarely could be noticed in some insignificant manifestations. For example, when we were passing together through Tbilisi on the way to a conference in Yerevan, he asked: "Let's go to the market. There one can buy homemade cheese, which is so like Italian cheese". Bruno liked the Caucasus: Armenia and especially Georgia. Something in the behaviour of people there reminded him of Italy. He had fiends among the highest Georgian intelligentsia.
Bruno learned to cook spaggetti and sauces to them in accordance with all the subtlies of Italian cuisine. I remember how he once invited me, A. Logunov, and A. Tavkhelidze to supper, and we learned how well he did this. It was very tasty (especially if one drinks Toscany wine "Chianti" with the food).
The first time Bruno was permitted to go to Italy was in 1979, it seems, after persistent presentations of the Italy-USSR society. At that time I was no longer in Dubna, and I found out from friends what difficulties had to be overcome in "pushing" for the trip to take place. First one, then another bureaucrat crossed Bruno out of the lists of delegations. Ultimately the bureaucrats allowed Bruno to go, fearing the imminent scandal.
Why Bruno was not allowed to go was quite clear. For the same reason that P.L. Kapitsa, L.D. Landau and many others were not allowed to leave the country. An acquaintance of mine was by chance present during a conversation between two clerks. One of them was explaining to the other, why P.L.Kapitsa should not be allowed to go out of the country. "In England he has a house and an account in the bank. Think it over. Would you come back, if you had a house abroad and an account in the bank?" These persons, who preached communist ideals and strictly followed the communist (religious) ritual, had long stopped being believers. They just held on as well as possible to their positions and priveleges, fearing to lose them, if anything happened. They were not capable of understanding that they were speaking of a great scientist and Russian patriot, that such people like P.L. Kapitsa, L.D. Landau, B.M. Pontecorvo could not leave their pupils and the schools they had created. These bureaucrats had caused an enormous damage to our science by isolatiing the most outstanding scientists from possible contacts with individuals of their own level abroad. One can only marvel that, in spite of the efforts of clerks, Soviet physics has achieved remarkable success. But this success could have been much more significant, if not hindered by such chameleons. The essence of many of them was revealed by the "perestroika", when some individuals, who were even in the highest positions of power, in the CC Politbureau of the CPSU, at the top of the KGB and were always ready to admire the actual "gensec" in power, started looking for relatives having experienced repression and telling how they suffered under the Soviet authorities and how they long had no belief in the communist regime. How, in any way, could these cynical non-believing priests of the communist religion understand that among the prominent scientists there could still be some "eccentrics" with principles? Therefore, in spite of apparent signs of respect, they never trusted Pontecorvo. Moreover, the clerks felt doubts arising: "Couldn't Pontecorvo happen to be a jew?" (When Bruno learned of such a supposition, he said: "I come from a catholic family", and stressed that in Italy (unlike the country of "real" socialism) people are distinguished only by their religion, not by racial or ethnic characteristics). So - welcome to the socialist countries. One can't escape from there. But before going, please, listen to instructions on how to behave abroad. We happened to listen to such instructions at the State Committee for atomic energy together with Bruno before our visit to Hungary. An intellectual-like KGB clerk from the Committee with gold-rimmed spectacles (he was said to hold the high rank of general) instructed us: "You may take two bottles of vodka with you. No more! There was a case. One respectable academician, we'll call him Ivan Ivanovich, wanted at any cost to take a box of vodka with him, saying that he just couldn't do without, abroad. No, we said, dear Ivan Ivanovich, you shouldn't do that. And he obeyed".
And we were compelled to listen to such bosh for a whole hour! Then we had to go to the State Committee for Science and Technology and there, also, listen to such instructions. I could feel Bruno boiling over with rage, but he restrained himself and even calmed me down saying that it was even worse before: "For inistance, at the general instruction before the Rochester conference held in Kiev in 1959 a Dubna representative of the regime pronounced the following: "Regretfully, it will not be possible to avoid contacts". The audience laughed. Someone started explaining that conferences are held precisely for contacts. Now he says to everybody that he is "for contacts". "I think, - added Bruno, - that visits abroad cannot be cut" (this was at the time of an increase of international tension, and restrictions were being imposed on "contacts"). Just look what a staff of civil servants profiting from them has been created. They wouldn't deprive themselves of work.
Several times Bruno visited Hungary to take part in excellent conferences on weak interactions and neutrinos organized by G. Marx. In particular, I remember the conference held in 1972. It was attended by R. Feynman, S.N. Yang, T.D. Lee, V. Weisskopf and many other outstanding physicists. Bruno and Feynman, as honorary participants, each planted a tree. At the conferences held in Hungary I could see the reverence and love Italian physicists felt for Bruno. He also spoke about many of them with admiration, often remembered his friends of the joint work with Fermi, was concerned for their success and failures. Of the new generation, he particularly liked Carlo Rubbia, whom he valued for his talent and for being an exceptionally bold physicist; he even liked the bravado characteristic of Rubbia. Bruno himself also liked to make jokes. When he was awarded the Etwos medal for work in neutrino physics, a lady-journalist asked him: "Is there hope that neutrinos will sometime benefit man?", Bruno answered: "Why "will"? It already benefits some, now".
We were glad for Bruno when he could freely visit Italy and meet with relatives, friends and colleagues. He was extremely touched that the Ferrara university (one of the oldest in Italy) elected him honorary professor, and Bruno prepared his introductory lecture very thororughly.
Having spent some time in Russia, Pontecorvo got to like its expanses and its people. He liked the Russian cuisine (he used to say it was better for him, than the French one). Bruno liked the openness, the broad-mindedness and kindness of the Russian character. Bruno's own personality, his charm and democratism attracted extremely diverse people: the doctors in hospitals liked him, the mechanics in laboratories, the waitresses in the canteen of the Academy and in the Scientists club. Many people, who felt sincere love and respect for Bruno, surrounded him. When we once crossed the Kamenny most (a Moscow bridge), he said looking from the bridge at the Cremlin ensemble: "I have been in many cities in the world, but believe me the view from here is the most beautiful I have ever seen". Being a polyglot, Bruno admired the Russian language and felt it extremely well (although he spoke it with an accent). He recalled the help in mastering the language rendered to him by Irina Grigorievna , who typed and corrected his articles. He always felt gratitude and much respect for her. It is interesting that for a long time Bruno could not understand the double negation existing in the Russian language. And he was quite amazed, when Migdal gave him an example of a triple negation: "It's impossible not to remember without a smile" (literal translation). For a long time I explained this phrase to him, and he was finally fascinated by this expression.
Bruno often remembered with piety his teacher E. Fermi and the entire group of Rome. He spoke of E. Majorana, whom E. Fermi himself considered a genius in physics, about his unpublished comments, about his mysterious fate. He prepared the edition of a collection of E. Fermi's works in Russian with extreme thoroughness. Much of what Bruno told me about E. Fermi was reflected in the comments he made to Fermi's articles in this excellent collection and in the book on Fermi written by Bruno. Therefore, I shall only present two of the comments.
Once, when I came to Bruno to discuss my calculations related to the diffusion of hydrogen mesoatoms, he exclaimed: "But that is Fermi's theory of age! Do you know why it is thus called?" I thought it was related to the life of a neutron after its production. "Not at all. There exists a well-known Italian joke: "A three-chimney ship leaves the port with a cargo weight of a certain number of tonnes and a certain number of passengers. The question is, what is the age of the captain?" That is where the name comes from". Further Bruno told me the following: "Fermi applied the age theory in creating the theory of a nuclear reactor. At the same time E. Wigner was writing integro-differential equations for the same purpose. Among his colleagues and friends, E. Fermi laughed at this: "Poor guy, how he suffers solving them". A simple physical approach permitted E. Fermi to obtain the sought result in a quite clear manner and with sufficient precision". "This does not mean that E.Fermi had not mastered the mathematical apparatus, - added Bruno, - he knew it extremely well and had published papers in pure mathemnatics. But he just considered that in dealing with a concrete problem in physics one must apply mathematics adequate to that problem and not complicate it with scientific-like "rigor" ".

Well, von Neumann was a person who E. Fermi admired. A close friend of E. Fermi in America (rather an engineer, than a physicist) told Bruno that Fermi answered a question concerning von Neumann as follows: "What do you think about me? Well, you must know that he is as more intelligent than I am, as I am more intelligent than you" (Bruno said this statement did not offend the story-teller, since they were friends with Fermi, and the difference between them was quite comprehensible to both of them).

Another interesting episode was related to Bruno himself. His work in Fermi's laboratory started with studies in classical spectroscopy, although he naturally aspired to work in nuclear physics. "Once I asked Fermi, - told me Bruno, - whether it would be possible to try to observe resonance scattering of -quanta in nuclear transitions? Fermi reflected a moment, then went to another room and, upon coming back after approximately ten minutes, he said it was impossible, owing to the recoil of the nucleus". I then joked: "Too bad Fermi stayed in the other room for such a short time. The point is that he had studied molecules and crystals before this and had even written a mongraph on this subject. If he had thought a bit longer, he might have thought of the Mossbauer effect. So there would have been one more work worthy of a Noble prize". Several times we discussed with Bruno how many works of E. Fermi might have been worthy of Nobel prizes, and counted five or six.
In connection with this Bruno's story I would like to tell a nearly similar story. In 1962, I.Ya. Pomeranchuk speaking of the Rochester conference held in Geneva (I.Ya. Pomeranchuk went abroad for the first and last time, then) recalled that Houtermans came up to him .
"Well, and what did he tell you?" - we asked. He said: "Chuk, we were idiots. We missed the Mossbauer effect". The point was that, in Khar'kov, Houtermans together with Pomeranchuk considered the scattering of neutrons in a crystal and knew of the possible existence of a non-shifted line due to scattering on the entire crystalline lattice.
When I told Bruno this story, he said that he knew Houtermans as an active German communist: "Like Georgii Dimitrov, he was exhanged in 1933 for some German agents". I was very surprised to hear this, because we had always read that the fascists were compelled to free Dimitrov from prison after his victory at the Leipzig process. "What, didn't you know anything of this? - said bruno, - well, then, consider I haven't told you anything". (Most likely, this was a well-known "secret" of the Comintern, which Bruno, nevertheless considered himself not be in the right to disclose).

Those and loved and revered Bruno were caused much sorrow by his illness, which was aggravated with time. When I come to Dubna, I used to visit Bruno to speak about physics and about "life". Once I saw he was upset. At a conference a reporter had attributed the idea of neutrino oscillations to some other people, and such references had already appeared in several papers. I laughed and said that his priority was known to everybody, but that the best and constructive answer to such insinuations would be a review, for instance in the Uspekhi Fisicheskikh Nauk, on the development of neutrino physics. Bruno answered that he would think of it, and he indeed wrote a very interesting and useful article. In parting he said: "You know I never cared about priorities. It's just that I'm ill and therefore nervous".
Bruno was very shy of his illness, of his "trembling", as he called it, which became especially bad when he was nervous. "How bad that precisely this illness attached itself to such a handsome and harmonious person like Bruno", - I heard from many. Migdal organized several encounters for him with the famous Juna, and Bruno, somewhat embarassed, said he felt some improvement after these sittings. Naturally, he didn't believe in any magic, but he actually noted her phychological influence and massage. Only she was wrong in telling him she had fingers that could feel neutrinos. That disillioned Bruno.
The last time I spoke with Bruno by telephone at the very end of July 1993, one day before he left Rome for Moscow. Bruno told me about the European conference on particle physics, about the report presented by L.B. Okun, which he liked very much: "Lev Borisovich is quite rigtht. The shutting down of SSC is not only a blow to physics, but also to the entire science, culture and civilization". Three weeks later it was the 80-ieth birthday of Bruno and together with friends we thought about how to celebrate it. I didn't know whether Bruno was to stay in Italy or to come to Dubna, but he said he was flying to Moscow the following day. "To be true, I have caught a little cold and feel quite bad, but I have decided not to cancel my journey", - he added. Just before his birthday I learned from my Dubna friends that Bruno was categorically against the organization of any jubilee and asked noone to come. I obeyed, siince it was Bruno's wish, but subsequently I regretted it very much: his friends gathered anyhow. Soon after Bruno was no more.
I consider it Providence, that I had the opportunity to meet with and to be a long-time friend of this extraordinary, great person.