Physicists have managed to register 17 rare decays of the kaon into a pion and a pair neutrino anti-neutrino in the framework of the NA62 experiment at CERN. The obtained value of the probability of this decay channel is within the error converges with the exact prediction of the Standard model and imposes severe restrictions on the search of theories beyond. On the new result, scientists said at an online conference ICHEP 2020, a press release published on the website of CERN.
In particle physics the Standard model is the main theory that very accurately describes a large part of the observed phenomena. However, during its existence, physicists have discovered many indications of incompleteness of the theory. In the Standard model there is no place for dark matter and dark energy, without the existence of which the scientific community is unable to explain the anomalously rapid rate of rotation the peripheral regions of galaxies and the accelerated expansion of the universe. A significant deviation from the Standard model and the violation of CP symmetry in the decay of K-meson, with the participation of the electroweak interaction, open in 1961.
K-mesons is a collection of four short-lived particle consisting of two quarks and containing one strange quark or antiquark, and K+ — positively charged meson in this group. From this particle a large number of different decay channels, and decay To the+ on positively charged PI meson, a neutrino and an antineutrino. On the one hand, it is extremely rare: 10 billion of various decays of positively charged K-meson has only one such decay. On the other hand, the probability is very accurately predicted by the Standard model, an error which in the determination of the probability of the channel does not exceed 10 percent. All this makes the decay K+-meson is very attractive to search for deviations from theoretical predictions, which could pave the way for New physics beyond the Standard model.
It is the search for the exact value of the probability of the decay K+ into a positively charged PI meson, a neutrino and an antineutrino is the main goal of NA62 collaboration at CERN. In this experiment the kaons are born in collision with a beryllium target beam of protons, pre-accelerated to an energy of 450 GeV Proton supersynchronous (SPS). In the area of detection flies the positively charged beam, 70 percent consisting of π+, 23 percent from protons and only 6 per cent of the interest of the experimenters To+. Using the detection setup with a total length of 270 metres of physics first, track the number of kaons produced in the collision of protons with the target, then with the use of triggers to select the decays of kaons needed for the calculation of the background and find the desired decay to a positively charged PI meson, a neutrino and an antineutrino. Special search complexity of this decomposition is due to the fact that neutrinos do not leave tracks in the experimental setup, because of what their presence in the decay have to be detected indirectly: through the angles and the flight speed of the source To the+ and the born-π+.