Charming ‘nesting doll’ for the collider: proposals by scientists from St Petersburg University are included in the European Strategy for Particle Physics Update

Scientists at the Laboratory of Ultra-High Energy Physics of St Petersburg University are working with colleagues at the ALICE collaboration. They are preparing to enter a new phase of work in a large-scale experiment designed to study quark-gluon plasma, which is a special state of super-hot and super-dense matter. It is thought to have existed in the early universe for a few millionths of a second after the Big Bang. New opportunities for direct registration of particles containing charm quarks in heavy-ion collisions at the CERN Large Hadron Collider (LHC) will significantly expand the horizons of future fundamental research.

The European Strategy for Particle Physics is a very interesting example of how the European scientific community selects, organises, and coordinates its efforts and works. The community is a collective of like-minded people involved in fundamental research in nuclear physics and high energy physics.

Grigory Feofilov, Head of the Laboratory of Ultra-High Energy Physics, Associate Professor of the Department of High Energy and Elementary Particles Physics at St Petersburg University

‘These include: fundamental and applied research in subatomic physics, practical applications for medicine and biology, instruments for astrophysics and space research, new materials, information technologies, popularisation of science, and academic programmes. Each organisation’s efforts – not only in the field of fundamental physics – augment the contributions made by the others. Together they help mankind to move forward,’ said Grigory Feofilov, Head of the Laboratory of Ultra-High Energy Physics, Associate Professor of the Department of High Energy and Elementary Particles Physics at St Petersburg University and Candidate of Physics and Mathematics.

Since 1992, scientists from St Petersburg University have been active participants in this scientific community. At the international conference on the LHC experimental programme regarding ultra-relativistic nuclear collisions in March 1992, our proposals for the two central systems of the ALICE detector won support. Since then, we have been actively participating in the work of CERN.

Grigory Feofilov, Head of the Laboratory of Ultra-High Energy Physics, Associate Professor of the Department of High Energy and Elementary Particles Physics at St Petersburg University

16 years passed since the 1992 conference before the Inner Tracking System (ITS) of the ALICE detector, which surrounds the beam pipe, was installed. For the next 10 years, this ‘heart’ of the ALICE experiment provided unique data at the LHC. Its main task is to track and identify charged particles, including strange and multi-stranged hyperons. The latter contain strange quarks that signal the formation of the quark-gluon plasma. The new proposals by physicists from St Petersburg University will be included in the new European Strategy for Particle Physics. They aim to facilitate the study of the processes of charm quark production, which will enhance our knowledge of the properties of the quark-gluon matter.

The ALICE detector is a 16 m high and 26 m long assembly of various detecting devices.

Grigory Feofilov, Head of the Laboratory of Ultra-High Energy Physics, Associate Professor of the Department of High Energy and Elementary Particles Physics at St Petersburg University

‘The whole experiment consists of about 20 different detection systems and is similar to a Russian nesting doll. Its innermost doll – the ALICE Inner Tracking System (ITS) – is the most complex. ITS must conform to the highest, strictest, and often mutually exclusive requirements. It was on this particular problem that the St Petersburg group focused in 1992. At present, new ideas are being proposed that will enhance physics capabilities with a major upgrade of the detectors. We will be able to register at a new level collision events, in which charmed particles, that is particles containing charm quarks, are born. We propose yet another world record in radiation transparency for this innermost, new ‘charming’ doll of ALICE. If we compare the ALICE detector to a microscope, then our ITS is the very first lens, the most clear and of the highest quality,’ explains Grigory Feofilov.

Undergraduate and graduate students of St Petersburg University participate in the work along with the scientists. The project has already been launched, and is scheduled to be completed by 2024. After that, the new ITS, developed by the St Petersburg University team for the ALICE experiment, will work at the LHC for about five years. The ITS will be installed in the ALICE detector, which is designed to: measure the charm quarks produced in the collision events of ultra-relativistic protons and nuclei; analyse various strange and charmed particles correlations; study the mechanisms of multiple particle production; as well as solve some other fundamental tasks.

‘This is the next important step that advances fundamental knowledge about the world. Indeed, fundamental research may also generate findings that have applications at a practical level,’ notes Grigory Feofilov.

Among the areas of applied research included in the European Strategy are hadron therapy and radionuclide diagnostics of oncological diseases, as well as the development of information technologies. According to Grigory Feofilov, these areas have been the focus of attention of the scientists and researchers at St Petersburg University for all these years. ‘The scientific knowledge gained from high-energy physics research can have a practical use. In medicine, for example, this led to the development of new effective methods in diagnostics and treatment. Hadron therapy is a breakthrough technology employed for treatment of both localised and metastatic cancer. Localised tumours can be targeted with protons and carbon ions with minimal side effects. This method has been gaining grounds in clinical practice in Europe and Japan, since it is believed to have an advantage over even the most modern x-ray methods. The radiation dose can be localised precisely within the tumour site, and the dose profile can be shaped to match the geometry of the tumour by using narrowly focused and scanned pencil beams of variable penetration depth. Furthermore, radionuclide diagnostics and positron emission tomography are by far the most accurate methods of early detection of oncopathology. The third application, which has been in use at the University for more than 15 years, falls under the latest information technologies section. This is the Russian segment of the Worldwide LHC Computing Grid, which is designed to handle the prodigious volume of data produced at the LHC.’

According to the scientist, one of the most salient aspects of the work is to ensure the continuity and high standards of the St Petersburg school of physicists, which remains one of the best in the world. ‘Over the past 10 years, while participating in the ALICE experiment, we have been studying matter at extreme energy densities and temperatures 100,000 times higher than the centre of the Sun. This special state of matter is also studied by undergraduate and graduate students at St Petersburg University. Our students are taught to analyse the latest and unique experimental data and theoretical models. This has important implications for both science and science education. Doing independent research projects students grow and develop. This is and always has been our University learning environment and teaching style. This is our tradition. I also grew and developed as a scientist doing experiments at the Leningrad University cyclotron. The fundamental knowledge and understanding that we gain today are projected onto the future of science,’ emphasises Grigory Feofilov.