Special issue. Rochester Conference in Dubna. 1964

Thoughts, reviews, impressions

The XII International Conference on High Energy Physics was over on 15 August. We are publishing a short report on the last two days of the Conference, where the reports of the rapporteurs on new techniques and ideas in the field of equipment for high energy physics were discussed.

Is it possible to do the impossible?

If the first and basic part of the Conference was dedicated what physicists in their laboratories were engaged in, what their research gave to science, then the last days of the Conference were dedicated to answering the question of how they implemented it and most importantly, what techniques and tools they intend to penetrate with into even deeper areas of the microworld.

One of the most advanced types of research facilities are the so-called bubble chambers. In them, passing through the thickness of the liquid, charged particles leave traces in the form of chains consisting of gas bubbles. These traces are photographed and subjected to subsequent investigation. Thanks to the photographs of traces in bubble chambers, more than one nuclear particle has been discovered, many patterns of the microcosm have been unraveled.

Bubble chambers are very complex engineering structures that combine the achievements of electronics, automation, optics, metallurgy, liquid gas technology and ultra-low temperatures. Until recently, it has been considered impossible to construct liquid hydrogen chambers with large volumes. Meanwhile, the volume of the chamber largely determines its value for science. But what seemed impossible yesterday is becoming possible today and will undoubtedly become possible tomorrow.

One of the main obstacles to the construction of large chambers was the difficulty of making large optical glass. Indeed, how to make a large optical glass for one of the walls of an "aquarium" filled with liquid hydrogen? For a chamber with a volume of 1-2 cubic meters, such glass can be cast with difficulty. The interior of the chamber is photographed through it. Therefore, the glass should be clean and uniform. Inside there is liquefied gas with a temperature of hundreds of degrees below zero, with constantly changing pressure. Therefore, the glass should be durable. But if the volume of liquid hydrogen in the chamber should increase to tens of cubic meters, then the difficulties of making glass will grow into a disaster that seems impossible to overcome.

At the Conference in Dubna, reports on how scientists and engineers came up with a simple and ingenious way out of the situation were delivered.

Why to make such huge glasses at all, they decided. Why not to make the entire "aquarium" out of durable metal, leaving only small glass windows for photography? It will be simple, cheap and durable. The first operating prototype of a liquid hydrogen bubble chamber of this type exists. It operates in Dubna in the Laboratory of High Energy Physics and has already produced about 30 thousand photos of nuclear "events". A simple principle, tested in practice, has been confirmed. Currently, projects for huge liquid hydrogen chambers are developed in different countries. In particular, American engineers have described a project for a chamber for 25 cubic meters of hydrogen (Brookhaven) and 20 cubic meters (Argonne National Laboratory).

Of course, there are many other difficulties to overcome when constructing large bubble chambers.

An interesting and original project for a liquid hydrogen chamber has been developed at the Laboratory of High Energy Physics. It is designed to observe rare events (neutrino experiments, investigation of rare types of unstable particle decays). The distinctive feature of the chamber is its elongated cylindrical shape.

Another new development is the project of positioning chambers in super-strong magnetic fields that will increase their resolution. Soviet and American scientists have reported on such projects.

Is it possible to stop lightning?

Before the inventor of bubble chambers Glaeser had even been awarded the Nobel Prize for his brainchild, an idea for an even newer and more promising research facility occurred, opening up broader opportunities for researchers. This is how spark chambers were born.

In bubble chambers, traces (tracks) of nuclear particles occurred in the form of chains consisting of gas bubbles in a liquid. In spark chambers, things are different. Flying between two electrodes, a charged particle ionizes the gas between them. It causes a discharge and therefore, an electrical breakdown, a spark, a small lightning bolt. By photographing the chamber, one can register the spark and therefore find out: here a particle flew.

A picture of remarkable progress in the design of spark chambers was revealed at the Conference in Dubna. It turned out that relevant achievements of fundamental importance have been made in the most recent times. Spark chambers have begun to answer the questions that worry physicists. The greatest contribution was made by scientists and engineers from Moscow, Dubna, Yerevan and Tbilisi.

The main innovation is the construction of so-called isotropic streamer chambers. This is what it means. Conventional spark chambers provided information about the particle's flight path only in two dimensions. No three-dimensional picture was created. It happened because the particles only ionized the gas and afterwards, a discharge occurred, during which the spark moved according to its own laws. It was clear that the particle had flown here. But in what direction - it was difficult to guess.

What if you stop the "lightning" at its very origin? Then a small fiery point will hang in the gas. And a dotted line of such points will show the entire path of the particle that can be photographed stereoscopically, in three dimensions. Soviet scientists proposed to instantly remove the voltage from the electrodes to stop the discharge.

But even it seemed insufficient. The experimenters wanted to know not only the number of particles that flew through the chamber, not only to measure the direction of their flight. Is it possible to measure the ionizing ability of the particle that flew through? It will provide additional information. Such chambers with large discharge gaps were constructed at the Institute of Theoretical and Experimental Physics (Moscow).

So, spark chambers are becoming smarter and more precise right before our eyes. Doctor of Physical and Mathematical Sciences A. A. Tyapkin reported on the latest achievements in this area at the Conference in Dubna. He also spoke about a new, even more advanced type of spark chamber constructed in Dubna under the supervision of Yu. A. Shcherbakov. This is a high pressure chamber.

Despite all their advantages over bubble chambers, spark chambers have one drawback. Particles fly through gas rather than liquid. The probability of their collision with the nuclei of the substance that makes up the gas is much lower, since the density of the substance is low. Consequently, not every particle will be registered. The efficiency of the device decreases. Scientists in Dubna decided to significantly increase the gas pressure in the chamber. The new type of chamber constructed here has a high efficiency of particle registration, as well as very high speed. The latter distinguishes it from bubble chambers. Another important property of the new device is controllability. The chamber registers only those events that interest the experimenter. And finally, it became possible to register particles with a very short range. The resolution of the device has increased.

To this day, the readings of spark chambers have been photographed for subsequent research. But in a number of countries, searches are underway for ways to automate the operation of chambers with the exclusion of all stages of photography.

At the Conference in Dubna, it was revealed that in different countries the search for a solution is carried out in different ways. In the USA and Geneva, a technique of sound location is developed, similar to how a person determines the location of a sound source using his ears (sensors located at two different points). Another group of scientists in Geneva tries to determine the position of a spark using an electrical location technique. In Dubna, they seem to have chosen a simpler way: measuring the amount of light from a spark using semiconductor sensors located at different points.

In all three cases, information about the particles should be converted into electrical impulses that are fed directly to a calculating machine. The researcher will obtain a complete picture of the results of the experiment, although he will not see its intermediate stages. The development of such techniques will provide a great saving of time for scientists and most importantly, will allow them to speed up the pace of experiments.

M. LEBEDENKO

"For Communism", No. 67, 1964

Our interviews with the delegates of the XII International Conference on High Energy Physics

In the world of elementary particles

At the XII International Conference on High Energy Physics in Dubna, our freelance correspondent V.Shvanev turned to Academician of the Academy of Sciences of the USSR Vladimir I.Veksler with questions.

Please, tell us about the issues that are currently discussed at this conference, the correspondent asked.

- It is very difficult to answer this question briefly. High energy physics is a field of science that studies the nature and properties of the simplest building blocks of matter - protons and neutrons, called nucleons, which the nuclei of all atoms are formed from. Until now, we have a completely insufficient understanding of the nature of these particles. Physicists do not yet know the structure of nucleons, do not know how nucleons are related to other particles of matter, for example, to the so-called mesons, how excited nucleons, called hyperons, are formed.

The sustainability, or as physicists say, the stability of these nuclear particles is extremely high. In order to study the nature of nucleons, it is necessary to act on them with flows of some atomic particles that possess very high energy, reaching billions and even tens of billions of electron volts... Only interactions at such high energies will provide new data about the structure and properties of nucleons.

What are the most relevant issues in high energy and particle physics discussed at the Dubna Conference?

- We can say that high energy physics currently includes two most significant sections: strong and weak interactions. Protons and neutrons, as well as various types of mesons that are produced during collisions of very high energy particles, interact strongly with each other. Studying the laws of this interaction is the task of the first section.

The second important circle of issues covers the so-called weak interactions. It has already been established that a very large set of processes concerning, in particular, the decay of all kinds of unstable particles of hyperons, K and Mu mesons and even the decay of neutrons can be understood from a certain general point of view. It turns out that there is a law according to which a certain class of particles called leptons is preserved in all nuclear processes. Phenomena involving leptons cover the section of so-called weak interactions.

At present, there is a hope that strong and weak interactions can be understood from a single point of view. Although we are still far from developing a general theory of elementary particles, indications on some general laws that are valid in both strong and weak interactions have gradually been developed. On the other hand, completely unexpected facts were reported at the Conference that may require a radical revision of some of the basic provisions of the theory.

What are the most interesting papers presented at this conference?

- It is very difficult to estimate the huge variety of papers presented by scientists from around the world. Two papers stand out at the Conference that are dedicated to the extremely interesting discovery of a new type of decay of the so-called KO2 mesons, carried out in laboratories in the United States.

The Conference is greatly dedicated to the issues related to strong interactions and especially new data on resonances. This is the name for strongly interacting unstable particles that decay into nucleons and mesons. Two years ago, at the previous International Conference on High Energy Physics in Geneva, Dubna physicists first pointed out the occurrence of multiparticle resonances, that is, unstable formations that decay into several secondary particles. Many new and diverse multiparticle resonances have now been reported and new types of these resonances have been established. This is also a large and very interesting group of investigations. Several interesting papers by the researchers of the Joint Institute and the Institute of Experimental and Theoretical Physics are dedicated to the investigation of resonances.

By the way, there are very interesting theoretical papers concerning the general laws of the world of elementary particles and a number of investigations extending the laws characteristic of strong interactions to the area of weak interactions.

Very interesting is the research that was carried out at the Institute of Experimental and Theoretical Physics of the USSR Academy of Sciences. In this research, the impact of weak interactions on nuclear processes was discovered for the first time. It has already attracted wide attention at the recent conference in Paris.

Finally, it is necessary to note new results concerning the structure of the nucleon. The investigation of the laws of elastic scattering of high energy particles, carried out by many laboratories, has given a number of new facts and in particular, confirmed the data on the so-called real part of the scattering amplitude.

Of course, I was able to list very briefly only a small part of all the interesting papers that were reported at various sessions of the Conference.

- In what areas, in your opinion, will high energy physics and elementary particle physics develop in the future? In what areas do physicists expect the best results?

- If it were possible to predict in advance in which areas the most interesting results would be obtained, then of course, we could save a lot of effort. The research front is extremely broad and surely, in all the areas I have spoken about, new and important results should be expected. However, in science it is not always possible to say in advance what will be the most interesting and significant for subsequent development.

- What significance does this conference have for the further development of international cooperation among scientists?

- It has become the most representative of all those that have been held so far. The Conference is attended by over 500 scientists from many countries of the world and it is a remarkable illustration of the fruitfulness of scientific cooperation. The Conference sessions lasted from 9 am until almost 9 pm. In addition to the official sessions, unofficial discussions are organized every day, dedicated to more specific issues. There is a very lively exchange of opinions in the corridors. It should be said that this conference is exceptionally indicative in terms of the fruitfulness of the exchange of scientific ideas, scientific cooperation and one can say, it has already yielded remarkable results.

"For Communism", No. 67, 1964

As to foreign scientists

V. Weisskopf, CERN Director General:

The International Conference on High Energy Physics was held very well. It was excellently organized by the local organizing committee, which we are very grateful for. The scientific results of the Conference are very interesting. I am glad that the scientists from many countries participating in the Conference learnt a lot of new things, as well as about interesting investigations and discoveries.

R. Marshak, professor of the University of Rochester:

- We held the first seven conferences on high energy physics at the University of Rochester (USA). When I came here, I was very touched to see a banner in the conference hall with the inscription "XII International Conference on High Energy Physics".

I would like to say that the Conference passed very friendly and at ease. This conference was very well organized. The problem of organizing a conference with 500 participants and 600 papers is a very difficult problem, much more difficult than organizing the first conferences that had 50-75 participants. The task of organizing this conference was difficult, but it was accomplished at a high level.

Physicists from different countries engaged in the field of high energies participate in the discussion of these problems. All this is to say that it was a wise idea to hold conferences not only in the USA, but also in the Soviet Union and Western Europe.

As for the atmosphere in which the conference was held, I will say frankly: the atmosphere was so cordial that I had the feeling as if I were attending a meeting of American physicists in America and not in another country.

In theoretical physics in the Soviet Union there are many qualified and hard-working people that carry out research at the world level. They are quite capable of competing with American scientists. I am very sorry that Professor Landau could not attend this conference due to illness. In the field of theoretical physics, he played an inspiring role, in particular at the Kiev Conference on High Energy Physics in 1959.

When we talk about experimental high energy physics, we should keep in mind that its development depends on accelerators. If there are high energy accelerators with high intensity, then good work can be done.

At present, the largest Soviet machine has an energy of 10 billion electron volts, while there are machines of 30 billion at the European Organization for Nuclear Research and Brookhaven (USA). Since these machines have higher energies, it is very difficult for Soviet experimenters to carry out experiments at the same level and at the same pace as in Europe and America. However, they work successfully and when a Soviet machine of 70 billion is constructed, the competition will intensify.

G. Bethe, Professor of the Cornell University:

The Conference Organizing Committee had a very difficult task - to put together a unified conference programme so that everyone would be happy. And it coped with this task brilliantly. We thank the Organizing Committee for the excellent organization of the Conference, as well as for the good organization of our vacation, in particular, for the walk along the Great Russian River Volga and the Moscow Sea. We were able not only to have a good rest during this walk, but also to exchange opinions on scientific issues.

"For Communism", No. 67, 1964

Meetings, talks, interviews

Cooperation between scientists will increase and strengthen

Edwin McMillan, Director of the Lawrence Radiation Laboratory at the University of California, Berkeley:

- The atmosphere at this conference was very, very good. We were welcomed very friendly and looked after well. The Conference was very interesting, several interesting results were reported that may change the views of physicists on the behaviour of elementary particles. In short, this is a very large conference and those that participated in it will remember it for a long time with interest and pleasure.

Professor Marvin Goldberger, Head of the delegation of American scientists:

- This conference is one of the largest international conferences on high energy physics that has been held since 1950. Many American scientists are delegates to the Conference for the first time in the Soviet Union. It was a great pleasure for us to take part in a conference that is so well organized (both in terms of the scientific programme and in other respects).

My scientific work is most closely related to the work of Soviet scientists that were pioneers in the investigation of reactions between particles at high energies. The talks with them here at the conference were inspiring. Soviet scientists have made a very large contribution to this field.

The value of this conference is that scientists could communicate with each other personally. The Conference made a great contribution to strengthening cooperation between Soviet and American scientists.

Dr. Peter Beckmann, Professor at the University of Mainz (Germany):

- At this conference, as at others, the results of the papers of small scientific groups from many countries were considered. Of course, individual papers were especially outstanding. First of all, it was an experiment confirming the non-conservation of parity and once again casting doubt on symmetry in the microworld. Another outstanding paper was the report of the Soviet academician Igor Tamm. He spoke about new ideas using which one can try to overcome the great difficulties in quantum field theory. The report was especially interesting for its author not only developed a large scheme with the help of which, perhaps, it will be possible to meet this issue, but he also gave specific instructions on the approach to these issues, not limiting himself to simple theoretical calculations.

Professor Arthur Clegg (England):

- At this conference, we had to deal with a large volume of papers. The most outstanding thing about the conference was that it dealt with the details of various problems of nuclear physics. At present, nuclear physics has reached such a level that the most important thing is to clarify various details.

Dr. Aladi Ramakrishnan, Director of the Institute of Mathematical Sciences, Madras:

- I have always dreamed of visiting the Soviet Union. We have heard a lot about your country. I have dreamed of scientific meetings. Finally, this dream has come true. In Dubna, I found myself in an atmosphere that allows scientists to exchange opinions on various scientific problems, provides an opportunity for close contacts and friendly communication.

It is well known that the Soviet Union has outstanding scientists, especially in the field of theoretical physics. I hope that our cooperation that currently becomes universal will strengthen.

Dr. Karl Heinz Altow (University of Bonn):

- We felt really good here. The Conference is well organized and most importantly, there are good opportunities for contacts between scientists from different countries.

We have a very good example of cooperation with Russian scientists. We currently carry out an experiment that was theoretically developed at the Lebedev Institute in Moscow. At the beginning of the Conference, we had a lively discussion with theorists from this Institute. We are very glad that we have the opportunity to discuss special issues with Russian colleagues.

Professor Kozuhiko Nishijima (Osaka, Japan):

- We had many discussions, they were held in a spirit of understanding. The Conference was a success, I hope that many more conferences will be held in the Soviet Union.

Professor Abdus Salam (Pakistan):

- High energy physics constantly develops. Research is carried out by many scientists from different countries. Summarizing the results of these investigations the Conference in Dubna is dedicated to, is of great importance for further progress. Participation in the Conference gave me great pleasure.

Dr. Andreas Kontogoris (Greece):

- First of all, I was very impressed by the excellent organization of the XII International Conference on High Energy Physics. In particular, the new system of transmitting simultaneous translation using miniature receivers used here is very convenient.

The opportunity to meet their colleagues, physicists from the USSR and other countries is very important for the Conference participants. In particular, meetings with Soviet scientists Gribov, Pomeranchuk, as well as Hungarians Domokos and Suranyi were very important for me.

I would very much like to come to Dubna to have the opportunity to work here for a long time. I hope that it will contribute to the improvement of relations between Greece and the Soviet Union.

Dr. Sulamith Goldhaber (University of California):

- I talked to many Russian physicists and enjoyed it very much. We talked about life. These talks were very useful for me. I was also at Russian physicists where we were invited. It was very nice. A good personal contact was established between us.

I should say that from the point of view of organizing the Conference, the Russians did a lot. The number of papers was enormous. It is difficult to summarize in five minutes the work that took two years. But it is not the fault of the Organizing Committee. It depended on the nature of the Conference and apparently, we should bring something new to the plenary sessions and to the general picture of the Conference.

As for our life in Dubna, everything was great here.

"For Communism", No. 68, 1964

Meetings, talks, interviews

We should develop cooperation

Professor Yash PAL (India):

- It was a great pleasure for me to attend the wonderfully organized conference in Dubna. This conference is organized every two years and this year, after a long break, it was again held in the Soviet Union. I also had the pleasure of participating in the Conference in Kyiv. And I should say that the Kiev Conference was wonderfully organized and this one is even better.

Dubna is in good natural conditions, on the banks of the Russian river Volga that is as close to the heart of a Russian as the Ganges is to us.

There were sensational announcements at the Conference, for example, further confirmation of the law of non-conservation of parity. We do not know what the consequences of this discovery will be.

We, scientists, have come here from many countries of the world and are engaged in various scientific problems. But when we gather together to discuss our investigations, we no longer care who came from which country. For us, there is no other way but that we should live in cooperation and peace.

There are great opportunities for cooperation between Indian and Soviet scientists. We held a conference on cosmic rays in Jaipur and Soviet scientists participated in it. A large number of the experiments that we carry out in India are also carried out here in the USSR. For example, we carry out an experiment in a deep shaft to register neutrinos. This is one area in which we could cooperate. We have favorable conditions for implementing neutrino experiments. On the other hand, the Soviet Union has large accelerators that we do not have. We are interested in working in the field of high energy physics. The Soviet Union is our closest neighbor that constructs large machines. This cooperation would be a very good addition to our good relations.

This is a wonderful country

During the International Conference on High Energy Physics, a group of wives of Conference participants got acquainted with Dubna. Here is what the wife of the famous American scientist E. McMillan, Helen McMillan said about her impressions of getting to know the city.

- It is very difficult to express our pleasure from getting to know everything that was shown to us in Dubna. We were in a kindergarten, in a nursery. I worked in the USA as a kindergarten teacher and therefore, I have the right to say: your kindergartens are very good. Your teachers are also good. I really liked the way they treat children. I liked the bedrooms, the dining room. The children sang songs for us. I also sang with them, I wanted to sing in Russian but unfortunately, I could only sing in English. In the kindergarten, they gave us toys that the children play with here.

We took a boat trip to a pioneer camp, where we saw children that practiced putting out a "fire," played and danced. The children greeted us with a song and gave everyone flowers. It touched us very much.

Our delegation also visited the hospital. There they put white coats on us and took us around different departments. We saw the operating room, the laboratory where they take blood, the maternity ward, the hall where husbands come to watch their newborn children on TV. We really liked your hospital. All this made an exceptionally great impression on us. On behalf of the wives of the Conference participants from Italy, France, Switzerland, the USA, Poland and England, I would like to say that we are very grateful to the referent Irina Romanova that showed us many interesting things.

If you allow me, I will share with you other impressions. We sailed on your amazing "Raketa". This is truly a great and new thing for us. We were going down the Volga so fast, to Kimry that we didn't notice the distance. On Sunday, together with our husbands, we took a long excursion on the Moscow Sea on a motor ship. We saw your beautiful pine forests, fields where you grow a lot of vegetables. You have a very beautiful country!

On behalf of the women of California, I ask: come to us to California. We will try to be as hospitable as you are in Dubna.

"For Communism", No. 68, 1964.

Our interviews

I believe in international cooperation

The famous Yugoslav scientist Professor Bogdan Maglich that participated in the XII International Conference on High Energy Physics said in a conversation with our correspondent:

- The most important achievements reported at this conference are the experiments of Cronin and Fitch (USA). They showed that the parity of charge conjugations is not preserved. In my opinion, these experiments are of revolutionary significance.

The second thing that I consider very important is the confirmation of previous reports about the discovery by Soviet physicists (that was reported two years ago) of the real part of the scattering amplitude. I will try to express it in simpler words. It was usually believed that it was sufficient to describe the nucleon-nucleon interaction or the pion-nucleon interaction only on the basis of the imaginary part of the amplitude. The occurrence of a strong real part of the scattering amplitude was first indicated by Soviet physicists from Dubna. (It refers to the research carried out at the Laboratory of High Energy Physics. The experiment was proposed by V.Sviridov and V.Nikitin. Soviet and foreign scientists took part in the research. - Ed.). It was carried out two years ago, but at that time their results were not believed and they were not accepted by scientists. However, these experiments were later repeated by Taylor in England, later, by Lindenbaum in America and Cocconi at CERN. They all showed that there is a very strong real part of the amplitude. I consider this a great success for Soviet physicists. The confirmation came in a surprising way from three experimenters almost at the same time. All these confirmations were reported at the Dubna Conference.

The important experiments discussed at the Conference in Dubna also included the occurrence of two types of neutrinos (Pontecorvo was the first to propose such experiments).

I will tell you about another interesting research. Two years ago, Soviet physicists from Dubna reported in Geneva that the so-called ABC resonance does not exist. They implemented very careful experiments. However, according to scientists, the ABC resonance was observed in many other experiments. Therefore, the Dubna results were not taken seriously. However, in 1962-1963, in Berkeley, Kirts and Tripp also came to the conclusion that this resonance does not exist. And finally, at CERN, in very careful experiments, Zavotini and his group absolutely clearly proved that the Dubna scientists were not mistaken.

After 1962, a number of unstable resonances and heavy mesons were obtained. They were mainly found in the USA and at CERN. This was a great success for CERN. I would like to point out that we brought reports from CERN to the Conference in Dubna that were signed not by individual scientists, but by universities in different countries. I was pleased to learn that such cooperation is also held in Dubna. I strongly believe in the possibilities of international scientific cooperation.

I was very impressed by the organization of this conference, the beauty of the city of Dubna, the hospitality we received and the friendly reception from our Soviet colleagues. The Conference was prepared very carefully.

It seems to me that the spirit of this conference will be continued and it will lead us to organizing other similar ones.

"For Communism", No. 69, 1964.