Switzerland records key symmetry breaking in baryons: a step towards unraveling the origin of matter

A team of physicists working with the LHCb detector at CERN's Large Hadron Collider has detected the first-ever reliable CP symmetry breaking in the decay of baryons, the fundamental particles that make up most of the observable matter in the universe, including protons and neutrons. This discovery has the potential to change our understanding of the nature of matter and bring science closer to understanding why our universe exists in its current form.

Речь идёт о CP-нарушении (нарушении зарядово-зеркальной симметрии) при распаде тяжёлого лямбда-бариона с b-кварком — частицы, состоящей из трёх кварков, один из которых относится к семейству “тяжёлых”. CP-симметрия предполагает, что частицы и античастицы должны вести себя идентично, если поменять их местами с отражением и поменять заряд. Однако реальность, как показывает эксперимент, нарушает эту симметрию.

Over the course of nine years, a team of researchers recorded decays of almost a trillion lambda baryons and their antiparticles, resulting in a statistically significant difference — about 2.5% - in the probability of decays between a particle and an antiparticle. Statistical confidence has reached the level of 5.8 sigma-this is above the generally accepted threshold of discovery in particle physics (5 sigma).

Previously, such effects were reliably recorded only in the decays of mesons-particles consisting of a quark and an antiquark. In the case of baryons, such deviations remained a theoretical assumption for a long time. The new result expands the field of possible sources of CP violation, especially those that go beyond the Standard Model of Particle Physics.

The value of the discovery lies not only in its scientific novelty, but also in its potential connection with the cosmological mystery of baryon asymmetry. According to the Big Bang models, matter and antimatter should have emerged in equal amounts, mutually annihilated, and left behind an empty universe filled only with radiation. However, observable reality is a world almost entirely made up of matter. Where antimatter is is an open question.

По мнению ведущих теоретиков, включая профессора Шона Кэрролла, этот результат — “небольшой, но важный фрагмент большой головоломки”, подтверждающий: барионы действительно способны нарушать симметрию и, вероятно, сыграли ключевую роль в формировании материи в ранней Вселенной.

Lead author Xu Ying Yang emphasizes that this is only the first step. To explain the scale asymmetry, additional sources of CP violation are required, which are probably outside the Standard Model. It is in this direction that research will continue at the LHCb and other advanced detectors operating on the edge of fundamental physics.

The discovery represents not only a scientific breakthrough, but also highlights the relevance of international cooperation and long-term investments in basic research. In the context of Uzbekistan, which is actively developing areas of nuclear and theoretical physics, such achievements form guidelines for the strategic development of science and education.