The LHCb collaboration at CERN has achieved a significant milestone in understanding matter-antimatter asymmetry by observing charge-parity (CP) violation in baryons for the first time. CP violation, which describes differences in the behaviour of matter and antimatter, was first observed in mesons in the 1960s but has remained elusive in baryons until now.
Using data collected from the Large Hadron Collider (LHC) during its first two runs (2009–2013 and 2015–2018), the LHCb team analysed over 80000 decays of the beauty-lambda baryon (Λb) and its antimatter counterpart (anti-Λb). They found that the decay rates of these particles differed by 2.45% from zero with an uncertainty of about 0.47%. Statistically, this result deviates from zero by 5.2 standard deviations, exceeding the threshold needed to confirm the observation of CP violation in this baryon decay.
This result provides a new way to study the fundamental differences between matter and antimatter, addressing questions about why the Universe is dominated by matter. However, the CP violation observed so far within the Standard Model is still too small to explain this cosmic imbalance, suggesting the possibility of undiscovered sources of CP violation. This finding opens the door for further theoretical and experimental research, both at the LHC and future particle colliders, to search for new physics beyond the Standard Model.
Professors F. Archilli and E. Santovetti from the Department of Physics participate in the LHCb collaboration, being involved in the management of the muon detector and the analysis of the collected data.
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