Measurement of matter-antimatter differences in beauty baryon decays

CERN-LHC. Differences in the behaviour of matter and antimatter have been observed in K and B meson decays, but not yet in any baryon decay. Such differences are associated with the non-invariance of fundamental interactions under the combined charge-conjugation and parity transformations, known as CP violation. Using data from the LHCb experiment at the Large Hadron Collider, a search is made for CP-violating asymmetries in the decay angle distributions of Λ0b baryons decaying to pπ−π+π− and pπ−K+K− final states. These four-body hadronic decays are a promising place to search for sources of CP violation both within and beyond the Standard Model of particle physics. We find evidence for CP violation in Λ0b→pπ−π+π− decays with a statistical significance corresponding to 3.3 standard deviations including systematic uncertainties. This represents the first evidence for CP violation in the baryon sector