MERIDIANS of cooperation

NICA in China: mutual interest,
strengthening cooperation, further discussions

On 10 - 13 September, the 2nd joint Russian-Chinese Seminar on the discussion of the NICA project was held in China. The event was organized with the support of the Chinese Consortium of organizations participating in the international collaboration established for the implementation of experiments on the multi-purpose detector MPD at the NICA collider. Completion of construction and launch of the experimental MPD facility are scheduled for 2025. The four-day scientific programme of the Seminar included sessions in Qingdao, as well as a discussion session held in Beijing.

The scientific session in Qingdao was organized by research teams from Shandong University, Fudan University, Classical University of Central China, University of Science and Technology of China and Tsinghua University in Beijing. The main organizers were Professors Chi Yang from Shandong University and Zebo Tang from University of Science and Technology of China. The discussion section in Beijing was organized by Professor Yi Wong from Tsinghua University with the support of representatives from the Institute of Modern Physics of the Chinese Academy of Sciences and the University of the Chinese Academy of Sciences.

The main objective of the joint Seminar was to bring together experimental and theoretical experts in relativistic nuclear physics from China and JINR to discuss the latest achievements, work plans and capabilities of the MPD experiment at the NICA collider, as well as its further modernization. The progress of construction and plans for the operation of the MPD facility, physical tasks and preparation for the analysis of the first experimental data from MPD, the results of research in the field of investigation of nuclear matter at high baryon densities in experiments at the RHIC collider (BNL, USA), the first results of the BM@N experiment at the NICA collider, as well as the goals and capabilities of upgrading the detectors of the MPD facility were discussed within the framework of the Seminar.

The first day of the Meeting in Qingdao was dedicated to the discussion of the current status and prospects for the development of the MPD experiment at the NICA accelerator complex. The current status of the assembly and integration of various detector subsystems, the results of thorough simulation of physical measurements at the facility, such as the investigation of polarization and spin alignment of particles, the production of hyperons and hypernuclei, were presented. The state of the MPD engineering systems, including the magnetic system and the status of the development of the internal tracking system ITS, carried out in collaboration with colleagues from the Classical University of Central China, were discussed. At the end of the first day of the Meeting, upgrade possibilities of the MPD time-projection chamber were discussed, including the use of new readout chambers. The colleagues from China shared their experience of participating in the upgrade of the detector subsystems of the STAR experiment at the RHIC relativistic heavy ion collider that preceded the second heavy nuclei interaction energy scanning programme, covering the energy range from 3 to 27 GeV. The presented results indicate both significant progress in the implementation of the large international MPD NICA project and the interest of the scientists from Chinese institutes and universities in this project.

The second day of the Seminar was dedicated to the discussion of theoretical and experimental research in the field of physics of relativistic heavy ion collisions at the energies of the NICA accelerator complex. The latest results of theoretical and experimental investigations of the phase diagram of strongly interacting matter in the high baryon density, the search for new phase transitions and the critical point were discussed. The participants also reviewed the latest results of the STAR experiment measurements: global polarization of hyperons, collective azimuthal fluxes, yield of hadrons, light nuclei and hypernuclei. In addition, the application of machine learning techniques to study various physical signals in the physics of heavy ion collisions, the possibility of new measurements of electromagnetic signals of strongly interacting matter and the implementation of the nuclear collision energy scanning programme at the NICA accelerator complex for various nuclear systems were discussed. The first results of the BM@N experiment on measuring the yields of strange particles and collective azimuthal fluxes of protons in Xe+Cs(I) collisions at a beam energy of 3.8 AGeV were presented. The status and research programme of the new CEE (Cooling-Storage-Ring External-target Experiment) experiment at the HIRFL accelerator complex (Lanzhou, China) were also presented.

The results achieved demonstrate progress in understanding the processes occurring in nuclear collisions and provide a basis for further research. Scientific groups from China have expressed interest in even more active participation in the MPD experiment. It is expected that the opportunity to study collisions of various nuclear systems at the NICA complex will significantly expand the results of the nuclear collision energy scanning programme at the RHIC collider that ended in 2021. After the shutdown of the RHIC collider in 2025, NICA will be the only centre in the world that studies relativistic heavy ion collisions in the energy range of 2-11 GeV.

The third day of the Meeting in Qingdao was dedicated to the discussion of the prospects for further development of the MPD experiment and its detector subsystems, as well as scheduled and prospective physical research. The possibilities of using the MPD facility in the fixed target experiment mode were discussed, proposals for upgrading the front part of the detector were presented, including a discussion of physical goals and possible decisions, as well as development of a new time-of-flight system for measurements in forward rapidity. At the end of each day, time was allocated for extra discussion of the reports, debates and summing up the results of the day.

The final day of the Meeting was held in Beijing, at Tsinghua University and was dedicated to the current state of cooperation between JINR and China within the framework of the NICA project, as well as to prospects for further development of the MPD detector. The event was an important occasion for discussing the current achievements and development prospects of the NICA project, as well as for strengthening cooperation between scientists.

It was decided to hold such seminars in China and JINR on a regular basis in order to strengthen the cooperation between scientists from JINR Member States and Chinese scientists, as well as to hold further discussions on a wide range of issues. A working group will be established to discuss the physics programme and the choice of design for the MPD forward spectrometers that are currently developed in the framework of its upgrade, with the ultimate goal of developing their conceptual design.

Based on the information from the JINR Press Office