SCIENTIFIC EDUCATIONAL CENTER science idea

During the first few millionths of a second after the moment of the Big Bang, the newly formed Universe was filled with high-temperature, trillions of degrees, boiling quark-gluon plasma. In the chaos of this plasma, quarks and gluons, colliding randomly, formed extremely short-lived X-particles, which quickly decayed back into their constituent parts. The explosive expansion of the Universe led to the subsequent cooling of the plasma, stable neutrons and protons began to form in its medium, which later became the basis of all matter. Currently, X-particles are a huge rarity, for the most part they occur only in the depths of accelerators, where high-energy collisions lead to the short-term appearance of quark-gluon plasma.

Recently, physicists at the Massachusetts Institute of Technology (MIT), together with their colleagues at the European Organization for Nuclear Research CERN, used machine learning and self-learning algorithms to “sieve” data collected during 13 billion heavy ion collisions in the interior of the Large Hadron Collider. Each of these collisions produced tens of thousands of new particles, and in this extremely dense and high-energy "soup" the researchers were able to detect traces of the presence of 100 X particles (3872). The number in brackets in this case means the estimated mass of this particle.

Note that this case is the first in history when X-particles were discovered in the environment of quark-gluon plasma and this gives hope to scientists to learn more about the structure and properties of these mysterious particles. Signs of the presence of particles X (3872) were first detected in 2003 during the Belle experiment at the Japanese particle accelerator in collisions of high-energy electrons and positrons. In such an environment, the X-particles decayed so quickly that scientists could not learn anything about the structure of these particles, but they had hope for a more thorough study of all this in the environment of a quark-gluon plasma.

So far, scientists suspect that particle X (3872) is most likely an exotic type of compact tetraquark, a subatomic particle made up of four quarks. However, the possibility is not ruled out that this particle is something like an even more exotic molecule, in which the role of atoms is played by two mesons bound to each other, subatomic particles consisting of two quarks.

In order to find traces of the presence of X-particles in heavy ion collisions, scientists had to implement several rather complicated things at once. The first is a detailed description of the X-particle decay images, on the basis of which the neural network was pre-trained. Secondly, with the help of mathematical filtering methods, scientists managed to reduce the level of background noise and interference by several orders of magnitude.

But the key point in all this was the use of an artificial neural network, which alone was able to extract signatures from the chaos of the creation and decay of more than a quadrillion short-lived particles resulting from a single collision.

In the results obtained by scientists, a clear peak was found in the mass region corresponding to the mass of particles X (3872). And the amplitude of this peak corresponds to the number of these particles in 100 units.

Over the next year or two, scientists plan to collect and process more data, which, according to their hopes, should shed light on the structure of the mysterious X-particles. If X(3872) is a densely packed tetraquark, it must decay more slowly than a pseudomolecule consisting of bound mesons. And now that scientists have a fairly reliable tool for detecting X-particles in the medium of quark-gluon plasma, this line of research will finally get off the ground.

Article published in the journal Physical Review Letters
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Source: dailytechinfo.org, sci-dig.ru