Seminars

Great prospects in a new area

On 30 April, Alexander Leonidovich SHCHEPETOV spoke at the JINR Scientists’ Club with a lecture "Cosmic ray research at the Tien Shan Alpine Station of the P. N. Lebedev Physical Institute".

The Tien Shan high-altitude scientific station of the LPI RAS (space station) is located at an altitude of 3340 m above sea level in the Tien Shan mountains. It includes large systems of charged particle detectors for registering extensive air showers (EAS) in the energy range from 1 to 1000 PeV and specialized hadron and muon detectors that allow one to study in detail the structure of showers and the properties of secondary particles. EAS are secondary particles resulting from the interaction of high-energy cosmic radiation with atmospheric atoms. A shower of secondary interactions caused by a single cosmic particle can have a diameter of tens of meters on the Earth's surface and consist of a million electrons, thousands of muons and only a few hadrons. The latter are of the greatest interest. And to observe all this, you need to be at an altitude of 3-5 km above sea level.

The experimental complex of the space station consists of two centres - "carpets" with densely located scintillation detectors. The first centre also has neutron and gamma detectors and a complex of underground detectors. The second is equipped with an ionization-neutron calorimeter. The speaker spoke in detail about the experimental equipment of the station, its modernization and the results obtained over the past 20 years. A. L. Shchepetov highlighted that in the investigation of elementary particles at such energies, a number of phenomena were observed that were not explained, including the violation of scaling in the nuclear interactions of cosmic ray particles. The speaker shared very recent results of simulating the parameters of the shower. In order to extract information about the muon components of the EAS, a muon scintillation godoscope was constructed at the station on the basis of modern technologies. It is still unclear why more muons are registered in cosmic rays than prototypes predict. In recent months, Alexander Leonidovich has been studying the composition of cosmic ray nuclei. As he emphasized, the experimental data of the station's underground laboratory and the simulation results (different prototypes) are in good agreement. The astrophysical aspect of cosmic ray physics is also studied - the position of their possible sources in the Universe. It has not yet been possible to see the sources.

Among the scientific tasks of the station is also the investigation of the physics of the Sun, heliosphere and near-Earth space; electrical phenomena in thunderclouds; monitoring of radiation background in the vicinity of the station and the investigation of these data in order to predict earthquakes. The speaker promised to introduce the details of these investigations at the next meeting.

DLNP Director E. A. Yakushev actively participated in the seminar. He commented for our newspaper, "Cosmic ray physics plays a huge role in physics in general. It had played a significant role before humanity managed to construct accelerators, that is, until the middle of the last century. At this time, some particles were discovered: the first antiparticle that was discovered was positron, muon and pion were discovered in cosmic rays. In the 1950s, the era of accelerator physics started, the first proton accelerator was constructed in Dubna, the best in the world at that time. This era continues today. It is on accelerators that scientists find answers to very important questions. For example, the answer was given about the nature of the mass of particles at the Large Hadron Collider with the discovery of the Higgs Boson, in which our Institute took an active part. At present, the NICA Complex is put into operation at JINR that will answer a number of questions of fundamental physics - about the quark-gluon plasma, what the nucleus is, what role gluons play and what role quarks play.

What is certain is that the next era of higher-energy accelerators seems currently inaccessible to humanity due to the fact that it is very expensive. Probably, cosmic rays will again begin to play a big role, since the energy that we detect in cosmic rays is many orders of magnitude higher than the energy that we can get on accelerators. The maximum energy of those particles that we see on the Baikal-GVD facility is hundreds of times higher than the energy on the LHC. It means that the investigation of cosmic rays has great potential for physics, including high energy physics. Surely, you need to reformat this area, redirect it in such a way as to get answers to the questions we face. And there are questions, for the Standard Model that functions great almost everywhere, should be expanded, since it does not explain a number of phenomena that we see. For example, it is clear to all physicists that you need to look for the answer to the question: what dark matter is and what dark energy is. Cosmic ray physics should develop in this area. It was not previously a traditional research area at JINR but with the development of a detector on Lake Baikal and the beginning of our participation in the TAIGA project that is aimed at studying cosmic rays - gamma rays, protons, muons, it has become such.

The space station differs from a number of other observatories of this type in that it allows you to observe a large number of all kinds of particles. Our colleagues and JINR employees from Kazakhstan have a laboratory near Almaty, on the Tien Shan, at an altitude of 3340 m. Our TAIGA laboratory is located at an altitude of 600 meters. They are very different in location, however, in the tasks they meet, they are very close. The Member State of the Institute shows great interest in carrying out further investigations. For it, the development of this field of fundamental physics and astrophysics is quite important. Both from the point of view of fundamental science and for educational purposes, since the observation of cosmic rays in the sense that it was done in the middle of the last century is one of the most visual techniques that can be used to teach students how to detect in high energy physics. This is the basis of education for the natural sciences, so such infrastructure in the Member State is relevant for the development of science.

Probably, the time has come at JINR when we can unite the efforts of various observatories. It should be said here that currently, the key results in this area are obtained on a large detector LHAASO that is located in the mountains of Tibet in China. These specialists join us to participate in the development of the next generation of the detector on Lake Baikal. Thus, three different groups are united under the JINR banner and it opens up great prospects for us to explore a new field of physics in the future - when we supplement the astrophysics data obtained on Lake Baikal with cosmic ray data from different observatories in Russia, Kazakhstan and China.

This high-altitude station near Almaty is still supported by the colleagues from LPI and Almaty. It seems to me that our joining this work, transferring our experience and borrowing the experience of our colleagues is very important. The best people should join forces in order to move physics towards new goals for meeting worthwhile problems."

After the seminar, A. L. Shchepetov added, "We are going to use the technologies that are currently developed at JINR in joint research with the Institute of Nuclear Physics (Almaty). At the initiative of Nurzhan Saduev, the production of detectors at INP has started. Our station should become an experimental site for testing these detectors and showing their efficiency in real-life conditions to meet current physical problems. The tasks, I suppose, boil down to the investigation of multicomponent cosmic rays at the level of information content that was previously unattainable by experimental technique."

Nurzhan Saduev (INP) commented, "INP, together with LPI RAS, is engaged in cosmic ray research. We specially came to JINR to participate in this seminar to discuss with colleagues the prospects for joint work. We understand that one visit will not be enough and if we consider the discussion that arose after today's report, there will certainly be a second. We will meet with colleagues and already in practical terms, we will discuss further research areas on cosmic rays."

Olga TARANTINA