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Physicists from CERN working on Large Hadron Collider, came close to answering why there was more matter in the early Universe than antimatter.
It is noted that the discovery made at the collider demonstrated that an elementary particle with an extremely short period of existence — lambda baryon decays at a different rate than a similar antiparticle. This is called a violation of CP invariance
This violation may explain why matter could have dominated antimatter in the early Universe, because otherwise the Universe would have been empty. Meanwhile, according to the Standard Model of particle physics, the number of CP-invariance violations is too small to explain such an amount of standard matter in the Universe.
Prior to this violation of CP invariance, only in particles made of quark-antiquark pairs, called mesons. This violation has not been observed in baryons, which consist of three quarks, in particular protons and neutrons, which make up most of the baryonic matter in the Universe. The discovery changes the way physicists think and paves the way for them to search for what lies beyond the Standard Model of particle physics.
«The reason why it takes longer to observe CP symmetry breaking in baryons than in mesons is due to the magnitude of the effect and the available data It took more than 80 thousand baryon decays to see the asymmetry of matter and antimatter with this class of particles for the first time», — explains the study participant, a CERN physicist Vincenzo Vagnoni.
The standard cosmological model assumes that after the Big Bang, the Universe was a hot plasma-filled space of matter and antimatter particles. They emerged and destroyed each other in the process of interaction. According to scientists, it was the violation of CP invariance during the decay of particles in weak interaction that led to the formation of much more matter than antimatter in the Universe in the beginning.
The researchers analyzed a large amount of data from collider experiments conducted from 2009 to 2018 and found convincing evidence that baryons are subject to mirror asymmetry.
The scientists analyzed the CP symmetry breaking during the decay of the beautiful lambda baryon, consisting of top, bottom and beautiful quarks. Physicists counted the decays of this particle as well as the decays of the anti-beautiful lambda baryon. The researchers then counted the number of observed decays of each particle and found the difference between them Their analysis showed that the difference between the decay numbers of the beautiful lambda baryon and the anti-pretty lambda baryon was 2.45% of zero with an error of about 0.47%.
The physicists say that, having recorded the discovery, they will look for even more CP symmetry violations, and collect additional data on the key mechanism that presumably allowed our universe to exist.
According to the scientists, the magnitude of the CP symmetry violation predicted by the Standard Model of Particle Physics is many orders of magnitude smaller than that required to explain asymmetries of matter and antimatter, that can be observed in the Universe. This implies the existence of new sources of CP-symmetry breaking, and hence, probably, new physics.
Source: LiveScience