The accelerator will reproduce the collision of neutron stars

NRNU MEPhI postgraduate students will take part in the experiment at the facility BM@N as part of the scientific complex “Nuclotron-NICA» in Dubna near Moscow. During the experiment, conditions close to those that arise in space during the collision of neutron stars will be recreated.

In September, six NRNU MEPhI PhD students will come to the Joint Institute for Nuclear Research (JINR) in Dubna to prepare and participate in an experiment during which cesium nuclei will be bombarded with xenon nuclei at energies from 2.3 to 3.5 gigaelectronvolts. As a result, conditions will be recreated close to those that arise in the Universe during the collision of neutron stars – unique astronomical objects, consisting mainly of neutrons, and characterized by enormous pressure and density: the mass of a typical neutron star is comparable to the mass of the sun with a diameter of 10-20 kilometers.

As the leading researcher of the Department of Condensed Matter Physics of the National Research Nuclear University MEPhI, Associate Professor Arkady Taranenko, the new experiment will serve to understand the processes occurring in neutron stars, which is important for a better understanding of the evolution of the Universe – after all, it is neutron stars that are largely responsible for the appearance of heavy elements in nature – such as gold, lead and uranium. But more importantly, the experiment should clarify the transition of matter into aggregate states unusual for terrestrial conditions that occur only at very high temperatures and energy densities – states that physicists call “strongly interacting matter.” In particular, we are talking about the so-called hadronic matter (a state when the matter no longer consists of atoms and molecules, but is a mixture of particles formed from quarks and antiquarks – mesons and baryons – interacting with each other), which, in turn, is a precursor to an even higher energy state of quark-gluon matter. In nature, such matter is formed only during mergers of neutron stars or in the center of supernovae.

Although these states of matter have already been repeatedly obtained on accelerators of various types, at present the task of scientists is to study the details of the phase transitions of matter from one state to another.

Scientists show particular interest in the little-studied region of energies of nucleus-nucleus collisions from 2 to 10 GeV. Experiments at such collision energies make it possible to achieve, under laboratory conditions, baryon densities exceeding the density of normal nuclear matter by a factor of 5–10. One of the key scientific tasks of international experiments at the Nuclotron-NICA accelerator complex is to study the properties of strongly interacting matter precisely at such high baryon densities.

Research at NICA is important for modern astrophysics. In 2017, for the first time, it was possible to detect signals from the collision of two neutron stars, both by directly measuring the gravitational waves caused by the merger of stars, and by measuring the electromagnetic radiation accompanying this process. Model calculations show that the merger of neutron stars produces nuclear matter, the baryon density and temperature of which reach values ​​similar to those observed in collisions of relativistic heavy ions in the energy range of the Nuclotron-NICA complex. Thus, with the launch of the experiments, scientists will have a unique opportunity in the laboratory on Earth to gain new knowledge necessary to understand the process of neutron star merger.

It is important to note that the Nuclotron/NICA accelerator complex with the MPD multipurpose detector and the Baryon Matter facility at the Nuclotron [email protected] is the largest project in the field of high energy physics for modern Russia.

NRNU MEPhI scientists actively participate in international collaborations [email protected] and MPD since their inception in April 2018. Their contribution to the work of the collaborations was recognized by the election of NRNU MEPhI employees to the executive boards of the collaborations. At the moment, NRNU MEPhI is the only Russian university whose representatives were elected to these councils.

The contribution of NRNU MEPhI to the experiments at the Nuclotron/NICA complex lies primarily in the study of the problem of the so-called collective particle flows, which has been studied by the scientific group created at the university since 2015.

The essence of this problem lies in the fact that particles that are born in the collision of nuclei flying with relativistic speeds do not scatter uniformly in all directions, but seem to have “preferences” for certain directions – or, as scientists say, the direction of emission of particles has a strong azimuthal anisotropy, depending on the dynamics of formation and the properties of a new form of matter. On these “preferred” directions, the particles form “collective flows”. In preparation for processing data from future experiments at the Nuclotron-NICA complex, the NRNU MEPhI research group is developing methods and algorithms for studying collective flows and creating the necessary software for this.

The participation of NRNU MEPhI in the work of the NICA collider is supported by the Priority 2030 program. Thanks to this program, leading employees of the National Research Center “Kurchatov Institute” and JINR are currently working at NRNU MEPhI. Together, preparations are underway for the next MPD (“Multipurpose Detector”) experiment, scheduled for 2024, during which particles will be dispersed to an even higher energy level than in the experiment [email protected] In particular, with the participation of MEPhI employees, software is being developed for the National Research Computer Network of Russia “NIKS”, which will process the data obtained during the experiments in Dubna.

Mona Platonov.

On the picture: MEPhI employees at the Joint Institute for Nuclear Research during a meeting of the MPD (NICA) collaboration in April 2022.

Photo zen.yandex.ru