The LHCb Collaboration at CERN has made groundbreaking observations that break charge-parity (CP) symmetry in baryons, offering insights into the universe’s matter-antimatter asymmetry. The findings are consistent with the Standard Model of particle physics but leave room for potential constraints on theoretical extensions.
Current cosmological models suggest a Big Bang that produced equal amounts of matter and antimatter, which should have annihilated each other shortly after the event. However, the universe now appears to be dominated by matter, with virtually no antimatter present. This discrepancy is not explained by the Standard Model, making it an intriguing mystery in physics.
Previous experiments, such as James Cronin’s 1964 work on neutral K meson decay, have demonstrated CP violation in weak interactions, indicating that matter and antimatter can behave differently. However, the effect is relatively small compared to what would be required to create the excess of matter observed in the universe.
The LHCb Collaboration has now observed this phenomenon in baryons, specifically in the decays of beauty (or bottom) baryons and antibaryons. These heavy particles were produced in proton-proton collisions at the Large Hadron Collider between 2011 and 2018. By analyzing multiple decay channels, the researchers looked for evidence of CP asymmetry.
Their findings indicate that the observed CP violation is consistent with the Standard Model but inconsistent with zero by a statistically significant margin (5.2σ). Other LHCb researchers examined alternative decay channels, finding results consistent with CP symmetry. While this data does not rule out potential extensions to the Standard Model, it provides valuable constraints on theoretical predictions.
Future studies at the LHC will aim to gather more precise measurements and potentially shed light on intermediate particles involved in baryon decays. This research has significant implications for understanding the universe’s matter-antimatter asymmetry and may help constrain theories involving dark matter.
Source: https://physicsworld.com/a/cp-violation-in-baryons-is-seen-for-the-first-time-at-cern