Bulgaria joined CERN in June 1999 as the laboratory’s 20th member state. An ECFA visit took place in September 2002 to find out about particle physics in the country.
Last September, the European Committee for Future Accelerators (ECFA) visited Bulgaria for the first time, as part of an ECFA mission to survey at first hand the status of particle physics in CERN member states. The visit was to Sofia, beautifully situated in a valley overlooked by Mount Vitosha and the Balkan range. Sofia has a history going back thousands of years, and counts the Thracian Serdi tribe, the Romans and the Byzantines among its previous occupants.
The academician Blagovest Sendov, a renowned mathematician and vice-president of the Bulgarian parliament, welcomed the committee. He recalled his own first contact with CERN; in 1986, as chair of the Bulgarian Science Foundation, he approved a grant of SwFr3 million (€2 million) for the participation of Bulgarian scientists and engineers in the L3 experiment at CERN. Sendov explained his appreciation of CERN’s important role in the development of science and technology in the modern world, particularly in Bulgaria. While praising the laboratory’s remarkable contributions in the domain of information technology, he recalled that the very first electronic digital computer was actually invented by an American of Bulgarian origin. John Vincent Atanasoff, who lived from 1903 to 1995, received a PhD in theoretical physics and went on to collaborate with electrical engineering student Clifford Berry, building what later came to be called ABC (the Atanasoff-Berry computer).
Following the welcoming ceremony, the status of particle physics and closely related areas was presented in a number of talks by Bulgarian scientists. A key player in the scientific research sector is the Bulgarian Academy of Sciences (BAS), which was formally established in 1911, but has its roots in a society founded in 1869. Today it is an autonomous national association, and runs a number of institutes, laboratories and other independent research centres. It funds and carries out research in collaboration with universities (primarily the University of Sofia) as well as independently. Its activities are organized in 11 departments, including physical, chemical, mathematical and engineering sciences.
Jordan Stamenov, director of the Institute for Nuclear Research and Nuclear Energy (INRNE) of the BAS, gave an overview of experimental high-energy physics in Bulgaria. The study of cosmic rays began as early as the 1950s by placing nuclear emulsions at an observatory situated on Mussala, the highest peak on the Balkan Peninsula (2925 m above sea level). Later, extended air showers in the energy range 1013-1017 eV were studied high in the Tien-Shan Mountains of Kazakhstan. The Mussala and Tien-Shan sites are still used for a variety of cosmic-ray and astroparticle physics experiments.
Bulgarian particle physicists initially carried out their research primarily using facilities in the former Soviet Union. Bulgaria was one of the founding states of the Joint Institute for Nuclear Research (JINR) in Dubna in 1956, and has been an active partner in many experiments there. From the early 1970s, Bulgarian scientists also began participating in experiments at CERN, mainly through JINR. For example, three Bulgarian physicists and one mathematician took part in the NA4 deep-inelastic muon scattering experiment in the 1980s, as members of the JINR group in the Bologna-CERN-Dubna-Munich-Saclay (BCDMS) collaboration.
Vladimir Genchev described Bulgarian involvement with the CMS experiment in preparation for the Large Hadron Collider (LHC). Bulgarians have been involved with CMS since the beginning, initially concentrating on the software. Bulgarian physicists did the Monte Carlo simulation of the CMS hadron calorimeter, and also took part in the optimization of its design and performance. Later they oversaw the production of the calorimeter’s brass absorber plates by Bulgarian industry. Bulgarians also took on major responsibility for the production, assembly and testing of 125 so-called resistive plate chambers. This is partially funded by the Bulgarian Ministry of Education and Science. Some 27 Bulgarian physicists and engineers have been involved in these efforts. Bulgarians also participate in the ATLAS project, as part of the JINR group.
Leander Litov of the University of Sofia reviewed Bulgarian participation in fixed-target experiments at CERN, such as NA48, NA49 and HARP. The Bulgarian group in HARP, for example, includes 12 people, and there are as many students participating in the experiments. Bulgarians also participate in the COSY experiments at Germany’s Jülich laboratory, where they study collisions between protons and light ions. This work has been partially funded through a bilateral agreement between Germany and Bulgaria.
Fulfilling potential
Bulgaria is a young nation in terms of higher education. The St Kliment Ohridski University of Sofia was founded as a Higher Pedagogical School in 1888. In 1904, by a royal decree from Prince Ferdinand, grandfather of the current prime minister of Bulgaria, the school was transformed into Bulgaria’s first state university. The University of Sofia is a leading institution for the education of young scientists, as well as for fundamental and applied physics research. ECFA delegates were impressed by the high level of scientific education of Bulgarian physicists, and by the quality as well as quantity of work they perform, in spite of a lack of resources. It was felt that there is a great deal of potential in the Bulgarian particle physics community, but not enough resources to realize it.
Matters related to LHC computing and the GRID project, from a Bulgarian point of view, were presented by Vladimir Dimitrov of the Faculty of Mathematics and Informatics at Sofia University. Bulgaria will not build a Tier 1 centre; a possibility that is being discussed is to create two Tier 2 centres for the Balkan countries – one in Greece and one in Bulgaria. One piece of good news is that there will soon be a 6 Mb/s data transfer line to the BAS, with the possibility of an increase to 622 Mb/s at a relatively small cost later on. It is very likely that all Bulgarian universities and research institutes will be optically connected to one another in the near future.
A a mutual smooth collaboration between CERN and the Bulgarian Ministry of Education and Science is of vital importance.
In Bulgaria, there are a number of small accelerators for industrial and medical applications. There is substantial know-how in accelerator physics, but funding is meagre. Furthermore, the facilities for medical physics and radiotherapy are inadequate given the health needs of the country. There is a strong wish to construct a neutron therapy facility, but this would mean overcoming obstacles related to the widespread fear of radiation in officialdom.
Matey Mateev, head of the Department of Theoretical Physics at the University of Sofia, reported on the status of theoretical physics in Bulgaria. Historically, almost all of the staff members in the field were trained at the Dubna, Moscow or St Petersburg theory schools. Research in theoretical particle physics is carried out at the University of Sofia, the BAS, the University of Plovdiv and the University of Shumen. The range of topics covered is broad, ranging from mathematical physics (for example conformal field theory) to topics directly applicable to experiments, such as the partonic spin content of the nucleon, or calculation of energy levels of the antiprotonic helium atom (studied experimentally by the ASACUSA collaboration at CERN). The Bulgarian theoretical particle physics community has strong ties with those in several other countries, in particular France, Germany, Italy, the UK and the US, as well as with CERN. Many theorists are grateful to Ivan Todorov for his pioneering leadership in creating a strong school of theoretical physics in Bulgaria.
Joining CERN in 1999 was a milestone for Bulgaria – it was essential not only for the development of high-energy physics in the country, but also for nuclear physics, electronics, informatics and other disciplines of importance for the future of the Bulgarian scientific community. This point was raised many times during the ECFA visit. The student representative, Stefan Piperov, also emphasized how he had been attracted to particle physics not only because of the fundamental nature of the subject, but also because of the opportunity to visit CERN. However, there was also a general feeling of discontent that promises given to Bulgarian physicists by the authorities had not been fulfilled. It was clear that the government faces a difficult economical situation. Nonetheless, it was also obvious that with more support, Bulgarian physicists, engineers and technicians could reach their full potential. To this end, a mutual smooth collaboration between CERN and the Bulgarian Ministry of Education and Science is of vital importance. The existing link between advanced technology and particle physics would then stimulate Bulgarian industry and technology, and be a valuable investment in the future economic development of the country.
