Japanese scientists experimentally showed the existence of exotic nuclei, which consist of two protons and a kaon.
Kaons – one of the types of mesons, composite elementary particles, which consist of quarks and antiquarks in equal proportions. Kaons contain one antiquark and one u- or d-quark; they are the lightest particles from the class of so-called strange hadrons.
“Sharpen” kaons are very difficult. The time of their existence is very short even in comparison with the life expectancy of other elementary particles. In physics, they are considered as a kind of virtual particles. But scientists have long assumed that, at certain intervals, kaons can form bonds with neutrons and protons, becoming part of the atomic nucleus.
Japanese physicists were able to detect such an “exotic core”. They managed to knock out a neutron and replace it with a kaon in the helium-3 isotope (a particle that consists of two protons and a neutron). Using recoil from neutron emission, scientists reduced the kaon energy and were able to achieve the formation of a kaon bond with protons.
“We have shown that mesons can exist in nuclear matter as real particles – like sugar, which does not dissolve in water,” said research leader Masahiko Iwasaki. Understanding the structure of such exotic nuclei will help scientists understand the origin of the mass of the nucleus and the processes that occurred in the universe after the Big Bang.