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yesterday

LHCb Detects First CP Violation in Baryon Decays

The measurement confirms Standard Model expectations; its small asymmetry cannot account for cosmic matter dominance, prompting plans to expand the dataset thirtyfold.

The LHC was essential for generating the vast quantity of beauty baryons and their antimatter counterparts required by the scientists.
Credit: CERN
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Overview

  • LHCb is the first experiment to observe CP violation in baryon decays by comparing Λb and anti-Λb particles.
  • Analysis of nearly nine years of data, encompassing almost one trillion beauty-lambda baryon decays collected between 2011 and 2018, underpins the finding.
  • Researchers measured a 2.5 percent decay-rate difference with 5.2σ significance, making a statistical fluctuation exceedingly unlikely.
  • Although the magnitude aligns with Standard Model predictions, it remains too small to explain why matter prevailed over antimatter after the Big Bang.
  • The collaboration intends to increase its dataset roughly thirtyfold in upcoming LHC runs to probe rarer decay channels and search for new sources of CP violation.