“SPD Days in Dubna” completed. What are the milestones?

Interview, 14 October 2020

A series of remote events called “SPD Days in Dubna” has finished at JINR. It was dedicated to the development of the project “Spin Physics Detector” at the NICA collider being constructed in the Institute. The series opened on 15 September with a meeting in the frames of which the SPD project was presented for potential new participants, as well as with a round table at which participants discussed the proposed further cooperation. On 30 September, a two-day workshop “Gluon content of proton and deuteron at SPD” started, and in a week, it was followed by the workshop “Physics programme for the first stage of the NICA SPD experiment”. Head of the SPD project Alexey Guskov told Jan Machonin about the progress and results of the “SPD Days”.

You have already spoken about the first stage of the event. Please, remind me why two more stages were needed?

The first meeting was almost entirely devoted to the presentation of the SPD project to potential future collaborators. We presented the emerging collaboration fields, discussed mechanisms using which it can be implemented. However, we consciously paid minimal attention to scientific issues postponing this discussion for the next events.

Fine. The second event: who did take part in it? What issues were discussed?

More than 100 scientists from world-leading scientific centres of Italy, France, Germany, the Netherlands, Japan, the USA, Portugal, the Czech Republic, Greece, Armenia, Russia, and JINR took part in the second meeting. 22 scientific reports were made, participants discussed both theoretical and experimental aspects of the study of polarized and non-polarized gluon structure of nucleons. A part of the reports considered the state-of-the-art of this field of physics. The other part of reports presented the current status of existing (COMPASS, STAR, PHENIX experiments) and planned (the electron-ion collider in the USA, the LHCspin project at the Large Hadron Collider in CERN, the COMPASS++/AMBER experiment) projects aimed to study the gluon structure of hadrons. I would like to note that all the reports were invited, the agenda of the workshop was carefully set and this ensured a very high scientific level of the event.

Were there scientific discussions during the meeting? How convenient is the video conference format for such kind of meetings? How did you manage to bring together people from different time zones?

Participants of the Workshop actively exchanged views and paid special attention to the application of the accumulated experience in the SPD project and the search for new tasks. The video conference format is not much different from an ordinary, face-to-face format. Except that in-person conferences include so-called “on the sidelines” discussions in addition to ordinary ones. However, despite this drawback, this format also has an obvious advantage: it is easier to gather people in such a format. In my opinion, the video conference cannot fully replace face-to-face conferences, but nowadays, when it is almost impossible to go on scientific trips, it is a worthy backup option. As for the time zones: yes, it was a really serious problem. The workshop started at 10 AM Moscow time and lasted almost until 7 PM. Colleagues from China and Japan were active in the first half of the day, and the Americans were mostly engaged in the event in the second half of the day.

Can you, please, highlight the most interesting ideas expressed at the workshop in terms of both spin physics and possible practical benefits for the future development of the SPD project?

I think I can. For example, theoreticians rightly emphasized the importance to study the polarized gluon structure in several different processes at once. I was impressed by the unique opportunity to have both collisions in the collider mode and interactions with a stationary target simultaneously at the LHCb.

I think that the most valuable practical advice was the following: not to repeat others mistakes neglecting the development of theoretical approaches that will be then necessary to interpret the results.

The third workshop was devoted to the discussion of opportunities to carry out various measurements at the initial stage of the SPD operation. Does it mean that the experiment has an additional scientific programme designed for the near future in addition to the major one?

It is true in a sense. The major programme is designed to study the gluon structure of protons and deuterons. The existing experimental facility is being optimized for this programme. However, the accelerator should achieve its maximum parameters to implement it: in terms of the collision energy, the collision intensity (luminosity), beam polarization, etc. It will happen gradually. Nevertheless, there are many other interesting scientific tasks we will try to solve at the SPD when the designed parameters of the accelerator will not be yet reached.

Please, tell me about the third workshop. Who took part in it? What scientific issues were discussed?

The last meeting was also very busy. There were 20 reports with proposals for various measurements. There were reports by physicists from JINR, IHEP, LPI, ITEP, PNPI, ITP, as well as by representatives of scientific centres of France, Germany, China, Egypt, the USA. Reports covered various topics: hypernuclei, spin effects in elastic scattering, collisions of light nuclei, multiparton correlations and states, search for new physics. I would say that the second workshop covered all the aspects of one topic, and the third workshop covered a wide range of completely different issues.

Can you single out one of the speakers?

All the reports were of high quality, although there were both eminent specialists and young researchers who had also achieved considerable results in their fields. By singling out someone I can unfairly offend others, but I cannot but mention such famous theoreticians as Daniel Boer (University of Groningen, Netherlands), Shunzo Kumano (KEK, Japan), Qiang Zhao (IHEP, Beijing), Mark Strikman (Penn State University, USA)… Of course, this is not a complete list.

Why are these workshops so important for SPD? Will all the suggestions made in the reports and discussions be taken into account?

First of all, we had an opportunity to share with the world spin community our ideas and plans, and, most importantly, to get feedback immediately. Now, we understand which plans we can implement, what is expected of us, and what is the common ground of SPD with other projects in this scientific field. We hope that theoreticians aware of our project will consider the idea to test their predictions at the SPD facility. For 4 days of meetings, we have received a significant volume of information, which should be carefully considered. Not every interesting proposal can be implemented at our experimental facility and not every idea that seems insane at first sight is actually insane. We have a lot to think about. I believe that after considering all the details, we will conduct discussions in private with authors of the most interesting and relevant ideas.

What are the results of the “SPD Days in Dubna”? Did it really make sense to combine several events in such a unique series?

In total, more than 150 Russian and foreign scientists from more than 20 countries took part in three events. So, this series will definitely increase the awareness and popularity of the SPD project in the world. I think that the idea to combine three events of different formats into a single cycle fully justified itself: it is a pleasure to see how newcomers who joined the first meeting then took part in scientific events. There weren’t many of them, of course. However, quality is more important than quantity. In addition, it is too early to sum up the results. I think that the past “Days of SPD” will have a lasting impact on the project’s development.