Horizons of scientific research

JINR - IHEP cooperation: a look through the years

This year, the 60th anniversary of the Institute of High Energy Physics (Protvino) is celebrated. It was established in 1963 with the aim of implementing fundamental research in the structure of matter and the fundamental forces of nature at a 70 GeV proton accelerator. On 7 October, 1963, Professor Anatoly Alekseevich Logunov was appointed Director of the Institute, Academician Nikolay Nikolaevich Bogolyubov was appointed Scientific Leader. To develop major international cooperation on the basis of IHEP, agreements were concluded, including with the Joint Institute for Nuclear Research. We are publishing fragments of an article written in 2008 by Adviser to LPP Directorate A.Volodko and Head of SSED S.Sychkov that provides an overview of joint work.

A huge contribution to the development of IHEP was made by JINR specialists. Even before the launch of the accelerator, a large group of leading Dubna scientists and highly qualified specialists, such as A.A.Logunov, A.N.Tavkhelidze and others moved to responsible areas of work at IHEP. Their professional knowledge, experience, as well as high scientific and engineering authority significantly influenced the rapid creation and establishment of scientific and technological teams at IHEP. In January 1968, at a meeting of the JINR Committee of Plenipotentiaries, Professor A.M.Petrosyants announced that the Soviet government provided scientists from all JINR Member States with the opportunity to work at the new accelerator. A bilateral agreement was concluded on the possibility of JINR specialists to implement experiments using beams from the U-70 accelerator and Directorate of the Institute decided to establish the Serpukhov Scientific Experimental Department (SSED). For its part, JINR ensured that the IHEP production base was equipped with first-class Czechoslovak machine tools and took part in the construction of industrial and residential buildings.

The newly established department had to act quickly. Already in April 1968, JINR set up an experiment to study the scattering of protons on protons and deuterons at small angles (Director V.A.Nikitin). At this facility, a "jet target" was developed and used for the first time in the world. As a result, just a year after the launch of the accelerator, JINR physicists, in joint research with IHEP, obtained the first preliminary information about the behavior of elastic proton-proton scattering in a previously inaccessible energy area.

In this experiment, a previously unknown pattern of changes in the radius of the strong interaction of protons at high energies was established that consists in the fact that the radius of the strong interaction of protons with protons at energies above 10 GeV increases with increasing energy (discovery No.244). It means that with increasing energy, the efficient radius of the proton increases and the proton itself becomes more transparent.

In experiments measuring the elastic scattering of protons on a deuteron, it was possible to obtain new information about the distribution of nuclear matter in the deuteron at high energies. These results aroused great interest in the scientific community and proved for the first time that the fundamental principles of the theory (causality, unitarity) are not violated up to energies of 70 GeV. The research was included in the cycle of investigations on the discovery of the "Serpukhov effect" and was awarded the State Prize. It should be noted that this team, together with its target, was invited to carry out a first-priority experiment at a supercyclotron with an energy of 400 GeV/c in the USA (Fermilab).

Soon, a facility was brought and installed to study the regeneration on hydrogen, deuterium and carbon of long-lived К⁰-mesons into short-lived К⁰-mesons (BIS facility, I.A.Savin, then BIS-2, M.F.Likhachev). Using this facility, systematic investigatins of the asymptotic behavior of the amplitudes of elastic forward scattering of neutral kaons were carried out for the first time.

At the same facility, a broad programme of research on short-lived charmed particles and a search for new narrow baryon resonances that decay into strange and ordinary particles were carried out. To process the huge amount of information from the BIS facility in SSED, an information and computing centre was established and developed, where information from all subsequent experiments was subsequently obtained and processed.

M.I.Soloviov - First Head of SSED, D.Tuvdendorzh (Mongolia), E.Kanarek (Poland), H.Semerdzhiev (Bulgaria)

This programme was implemented in subsequent years at the new EXCHARM facility (V.D.Kekelidze) that was specifically designed to study the production of strange and charmed particles in a beam of high energy neutrons on a special channel of the U-70 accelerator. As a result, new important results on the properties of the birth and decay of these particles were obtained for the first time.

In the same years, a joint JINR - IHEP - USA experiment on the scattering of π^- and К^-- mesons on electrons was carried out (E.N.Tsyganov). In this experiment, the efficient radius (form factor) of unstable π- and K-meson particles, whose decays do not involve nucleons, was directly measured for the first time. The size of the form factor turned out to be approximately the same as that of a nucleon, with the same energy of the incident particles. The experiment was based on an original technique that was subsequently successfully applied in joint experiments at the accelerator in Batavia (USA).

Headed by V.I.Petrukhin, a facility was developed to search for heavy particles and antinuclei that culminated in the discovery of antitritium.

From JINR to IHEP, a two-meter heavy liquid bubble chamber was transported and installed to study the interaction of π^--mesons with protons and carbon nuclei (Directors M.I.Solovyov and V.G.Grishin), as well as the largest two-meter liquid hydrogen chamber in the USSR "Lyudmila" to study p- and p-interactions (I.M.Gramenitsky and N.M.Viryasov). As a result, new patterns in the production of particles at high energies were discovered for the first time.

When studying the properties of antiproton-proton interactions at a momentum of 22.4 GeV/c, the alignment of the ρ-meson spin was discovered that directly proved the occurrence of polarization of quarks at the stage preceding their combination into a meson. Using a track-sensitive liquid deuterium target inside the working volume of the chamber of "Lyudmila", data on the properties of the main characteristics of previously unstudied antideuteron-deuterium collisions at an energy of 12 GeV were obtained.

Using a specially developed five-meter spark spectrometer installed on a 40 GeV beam (MIS-1 and then MIS-2 facilities, A.A.Tyapkin), the occurrence of new unstable excited states of the π-meson, decaying into three ordinary π-mesons, was reliably established. The mass of these new particles is 1240 and 1770 MeV, that is, many times greater than the mass of an ordinary π-meson in its ground state.

Processing of the enormous (mainly film) experimental material obtained at these facilities was carried out in many national institutes of the JINR Member States. Thus, a new form of scientific and technological cooperation was established that was expressively called "physics at a distance." It allowed to involve teams in implementing research at the cutting edge of knowledge that would not have been able to carry out such work independently.

From the first days of operation of U-70, the investigation of polarization effects in the area of the highest energies at that time started at the Proza-Polarimeter facility jointly developed by JINR and IHEP (Yu.M.Kazarinov). An important feature of this facility was the large polarized "frozen" target developed at JINR headed by B.S.Neganov that could operate in two versions - proton and deuteron that significantly expanded the range of polarization phenomena studied. As a result of investigations of polarization effects in charge exchange processes, the complex dependence of polarization in pion-proton scattering with charge exchange was established for the first time and experimental evidence of the important role of spin at high energies was obtained.

A large programme of joint IHEP - JINR research of hypercharge-exchange reactions was carried out at the HIPERON facility (Yu.A.Budagov and V.B.Flyagin). The facility was aimed at studying the dynamics of processes with very small cross sections based on very large statistics. In this experiment, in addition to new scientific information about the properties of hypercharge-exchange reactions, important information was obtained about the quark composition of the η-meson and the upper limit on the probability of the decay of a short-lived neutral kaon into an electron and a positron.

The investigation of the properties of the production and decay of relativistic positronium, devloped as a result of the rare, previously unobserved decay of a neutral π-meson into a photon and positronium, was carried out in the Positronium experiment (L.L.Nemenov). To register positronium, three-meter drift chambers were developed and constructed, in which the self-quenching streamer discharge mode proposed by JINR specialists was used for the first time.

A number of important physical results were obtained in joint JINR - IHEP experiments under the SIGMA-AJAX programme (G.V.Mitselmacher). The so-called Compton effect on the π meson, previously registered only for stable particles - proton and electron, was studied in detail. In the experiment, the fundamental structural constant of pion polarizability was measured for the first time. In parallel, the process of development of pion pairs using pions in the Coulomb field of nuclei was also studied.

Participants of the joint SIGMA-AJAX experiment on the channel of the Serpukhov accelerator

These investigations complement experiments on neutral pion decay and allow to directly test both the color SU(3) theory and the anomaly hypothesis in chiral theory.

In Dubna, a "Neutrino detector" (S.A.Bunyatov) was developed and installed on the U-70 facility to study the interactions of neutrinos with nucleons and electrons, as well as to search for events indicating neutrino oscillations.

In the first years of U-70 operation, JINR scientists carried out a range of search experiments, including a search for the occurrence of a Dirac monopole (V.P.Zrelov), short-lived particles (TAU facility, L.S.Zolin), anomalously long-lived strange particles (B.M.Pontecorvo), research of rare and radiative decays of К^-- mesons (ISTRA, B.Zh.Zalikhanov).

In total, since 1967, IHEP has accepted and approved about 175 experimental proposals. As Academician A.A.Logunov has noted, JINR scientists have prepared and carried out more than 50 experiments. This is about a third of all experiments at the U-70 accelerator and a third of the accelerator's operating time for a physics experiment.

JINR Weekly No. 4, 2008
Photo and poster by Yu. TUMANOV

From the first days of work of SSED until May 2006, the permanent Deputy Head of the department has been Yuri Grigorievich Basha.

He has participated in the preparation and implementation of all JINR experiments at the U-70 accelerator at IHEP, has supervised the supply of equipment, installation of experimental facilities, has headed construction work and has met engineering and technological issues in the development of experimental facilities. His responsibilities have also included creating optimal conditions for the fruitful work of JINR experimenters and employees of SSED in Protvino - from solving housing and everyday problems to organizing medical care.

To a large extent, thanks to his efforts, SSED was provided with energy supplies during the difficult years of perestroika. In addressing some life support issues of the department, the experience of Yu.G.Bashi is simply irreplaceable. He has made an invaluable contribution not only to the establishment and development of the department, but also to the expansion of cooperation between JINR and IHEP.

Weekly No. 43, 2008