International Nature of Particle Physics

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INTERNATIONAL NATURE OF PARTICLE PHYSICS

Nature's laws are universal, and logic and experiment prevail in their formulation. Their validity ignores national boundaries and cultural differences. Research in physics has therefore always demonstrated an international character, and peer recognition at the international level has been eagerly sought. However, whereas the dissemination of new results and ideas through international journals and international conferences has always taken place, original work long originated from individuals or small research groups with their distinct national styles.

By the beginning of the twenty-first century, particle physics experiments in all the major laboratories of the world had become truly international ventures, drawing researchers from around the world to participate. Particle physics has played a leading role in enhancing a more pronounced internationalization of science, with the pooling of resources from individual nations and its requirement of large international teams of scientists working together to obtain new results. The European Laboratory for Particle Physics (CERN) in Geneva, Switzerland, provides an ideal example of this internationalization not only because it draws researchers from around the world but also because it was created by a collaboration of nations.

The Creation of CERN

CERN indeed illustrates well the success of international scientific collaboration. This first looked possible in those academic domains with no immediate applications but where several neighboring nations were still interested in developing their research in an important way. This was the case for particle physics. The need for this new way to do re-search was first strongly realized in Europe after World War II, when it became clear that needed instruments were financially out of the reach of individual nations. In 1949 French Nobel laureate Louis de Broglie made a vibrant appeal for an international laboratory where physicists from different European nations could work together. Encouragement from prominent American physicists culminated with the address of Nobel laureate Isidor Rabi to the United Nations Educational, Scientific and Cultural Organization (UNESCO) conference of 1950 in Florence. The response took only a few years to materialize; in 1954 CERN was created.

International collaboration in Europe first appeared to be most needed for the construction and operation of large accelerators, and the purpose of CERN was to build a laboratory for the study of elementary particles with high-energy accelerators in Western Europe. The facilities offered to European scientists had to compare favorably with those available in the United States (e.g., the Brookhaven National Laboratory) in order to attract physicists. In a period of time, a "pyramidal approach" was considered where the base was the universities, the middle level the national laboratories with their medium-size machines, and the top CERN with the largest machines. However, natural evolution soon eliminated most of the nation-based machines in Europe, leaving the national laboratories dependent on CERN for re-search in particle physics. The Deutsches Elektronen-Synchrotron Laboratory (DESY), in Germany, has remained a national laboratory with top-class machines, but it is used on an international basis, and several countries contributed to the construction of its newest machine, HERA. Very soon also after its creation, all experimental groups at CERN involved physicists from different institutes, in different countries, working together, building detectors and exploiting them. Full international collaboration thus became a new style in research.

Back in the early 1950s it was difficult for the promoters of CERN, such as Pierre Auger and Eduoardo Amaldi, to convince many of their colleagues that pooling resources (financial and also human resources) in a common endeavor was the only way to progress. Some indeed argued that any extra international funding should be distributed among the existing national structures. However, eventually, everyone was convinced that full European collaboration centered on an international laboratory was the proper choice.

Scientists from different countries and backgrounds worked together. They decided together what to build, how to construct accelerators and detectors, and how to exploit them best. In that way, they found they had to learn much from each other, breaking national and cultural boundaries. This was not always easy, but the benefits of pooling resources and ideas were soon realized. Nobody would any longer say that the national resources that are transferred to CERN by its member states should rather stay in the home nation, and nobody would any longer consider a purely national experiment in particle physics. In Europe, the example set by CERN was eventually followed in other areas of research: ESO (the European Southern Observatory for astronomy, ESA (the European Space Agency) for space research, the ILL (the Langevein-von Laue Institute) and the ESRF (European Synchrotron Radiation Facility) in condensed matter physics, and the EMBL (European Molecular Biology Laboratory in biology.

Working at the International Level

Proper collaboration at the European level called for the implementation of new and flexible decision-making structures. They have been working well. Physicists have the great advantage of sharing the same passion and speaking a common language. Yet, what was achieved at CERN can also serve as an important, fruitful example for other professions.

For instance, any decision on the construction of new machines has not been left to CERN alone but has involved international discussions and reviews, and an international body was created representing the users of the laboratory in its member states. It was called the ECFA (the European Committee for Future Accelerators). One may summarize by saying that European physicists gradually learned how to fully collaborate on their research in particle physics, and, in that respect, Europe has paradoxically shown far more unity than the United States, where resources were distributed over several large laboratories. The concentration of resources at the CERN site has allowed the construction of many machines of a new type, unique in the world, such as the Intersecting Storage Rings in the 1970s, the proton-antiproton collider in the 1980s, the LEP machine in the 1990s, and most recently the LHC, now under construction and scheduled to be completed in 2007. These unique machines have attracted many scientific users from all over the world and, in particular, from the United States, bringing an international world dimension to an initially European endeavor.

Since it quickly grew from small to big in both size and budget, CERN was granted a very large amount of autonomy from the outset, control from the member states being essentially present at the global budget level and for the approval of new major projects, but not in the ongoing operation and research programs of the laboratory. This contributed much to its success as an international organization. Yet, in the beginning of the twenty-first century, one now sees nations less willing to grant the same liberty to newly created agencies, instead preferring to maintain a stronger control. Sometimes national officials have to be reminded that CERN is their country's own laboratory for particle physics and not a foreign institute drawing on their financial resources. Thus, international collaboration, which European physicists have learned to appreciate so much, still calls for lasting effort and cannot simply be taken for granted.

Opening to the East and to the World

The collaborative spirit of CERN was quickly extended to the East. Anything that could be done to bring together physicists from the West and from the East during the tense Cold War years was extremely beneficial in paving the way, in a modest but tangible manner, to the eventual thaw. Soon after the creation of CERN, the countries of the eastern block established an international laboratory, the Joint Institute for Nuclear Research, in Dubna, near Moscow. Some collaboration between CERN and Dubna started in a modest way in the late 1950s; however, it quickly developed. For example, through over 20 years of East-West confrontation, CERN and Dubna formed a joint school that every other year brought together for two weeks fifty young physicists from the East and as many from the West. More importantly, European groups worked at the large Soviet laboratory Serpukhov in the early 1970s, and many Soviet groups later worked at CERN as part of large international collaborations. It took courage and good will to exploit any crack in the Iron Curtain, but the effort paid off. CERN and Dubna were both nominated for the Nobel Peace Prize in 1997. Physicists were talking physics, but they were also talking about Andrei Sakharov and Yuri Orlov! They were first of all getting to know one another.

At the beginning of the twenty-first century, some cooperation in particle physics extends to the whole world. It is partly monitored by ICFA (the International Committee for Future Accelerators), and worldwide research collaborations are often at work for research. It was strongly the case for the LEP experiments and is extending further for the LHC experiments.

International collaboration between western Europe and the United States has always been strong. It first included European and American physicists as individuals, mainly many Europeans learning particle physics in the United States, and some Americans coming to Europe on sabbatical leave, but, by the 1970s, this connection had already turned into full university groups with professors, postdoctoral physicists, and students working for several years on the other side of the Atlantic within the context of international collaborations. By the 1980s, with the unique machines at CERN, the number of American particle physicists in Europe eventually became much larger than that of their European counterpart particle physicists in the United States. The United States, together with Japan and other countries, has agreed to contribute to the construction of the new LHC at CERN, extending scientific collaboration beyond the European nations. Additionally, starting in the 1970s, Fermilab, in Batavia, Illinois, made a big effort to associate to its research not only Europeans but also scientists from the Soviet block, from Asia, and from South America.

An Example of International Experimental Collaboration

A good example (among many) of international collaboration is offered by the L3 detector at LEP, built and operated under the leadership of Samuel Ting from MIT. It shows how collaboration in particle physics can shatter barriers for the benefit of a scientific endeavor. Crystals of bismuth and germanium oxide (BGO), for detecting gamma rays and electrons, were a key part of this big LEP detector that was built by a collaboration of physicists from seventeen countries. The team consisted of several hundreds physicists from western and eastern Europe, the United States, the Soviet Union, and Asia, with researchers from China and also from Taiwan. The construction of the detector required 12 tons of BGO of high purity, something never before realized at that level. This called for the joint effort of 100 physicists and engineers from China, France, Germany, the Nertherlands, Italy, the Soviet Union, Switzerland, and the United States. Any reluctance generated by national sensibilities were overcome, and the Soviet Union agreed to provide 5 tons of germanium oxide, a product deemed "strategic" at that time. China brought in the necessary quantity of bismuth oxide, and the ceramic institute of Shanghai produced in two years the required number of crystals, over 10,000 altogether. Machines for cutting and polishing the crystals and also those to control the achieved quality were built in France and shipped to China in the early 1980s. Production commenced in 1985, and the crystals were delivered to CERN in1987. Everything was ready by 1989 when LEP started. The sophisticated electronics coupled to the crystals came from the United States.

This key piece of the overall detector was an important element in the success of the L3 experiment. The BGO crystals and their associated electronics were also quickly found to be useful in increasing, in an important way, the power of the positron emission tomography (PET) machines (an earlier spinoff of CERN), which play a great role worldwide in cardiology, neurology, and oncology. None of this could have been achieved without much good will, but also the motivation, generated by the challenges of physics.

Physics as a Link among People

Since that the East-West cleavage has happily largely disappeared, it is natural to find particle physicists at the origin of new endeavors, in particular, attempting to draw together scientists from the countries of the Middle East to an international laboratory built for a synchrotron radiation source. This would be a highly upgraded machine made from one recently decommissioned in Germany and offered for that purpose. This budding project, named SESAME, is trying to take shape with the help of UNESCO. It is no longer particle physics, but particle physicists led the way. Indeed, all this started with the efforts of Sergio Fubini of CERN and Turin, who organized a first, and very fruitful, meeting in the Sinai, in 1995. This one week physics conference brought together Egyptian, Israeli, Jordanian, and Palestinian physicists together with their American and European colleagues. It was followed two years later by another one in Turin where the SESAME was first discussed. It is hoped that participation in this project, a major common endeavor, will result in other collaborations among these nations. They may find with physics the possibility to get to know one another, and this may lead—let us hope—to a better understanding.