Abstract (data abstract)

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 $\Lambda^0_b$ baryons decaying to $p\pi^-\pi^+\pi^-$ and $p\pi^-K^+K^-$ 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 $\Lambda^0_b\to p\pi^-\pi^+\pi^-$ 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.

Table 1

Data from Table 1

10.17182/hepdata.76921.v2/t1

Binning scheme A is defined to exploit interference patterns arising from the resonant structure of the decay. Bins 1-4 focus...
Table 2

Data from Table 1

10.17182/hepdata.76921.v2/t2

Definition of binning scheme B for the decay mode $\Lambda_b^0\to p\pi^-\pi^+\pi^-$.
Table 3

Data from Table 2; Fig. 4a

10.17182/hepdata.76921.v2/t3

For $\Lambda_b^0\to p\pi^-\pi^+\pi^-$ decays, the CP- and P-violating observables, $a^{\hat{T}-odd}_{CP}$ and $a^{\hat{T}-odd}_{P}$, resulting from the fit to the data are...
Table 4

Data from Table 2; Fig. 4b

10.17182/hepdata.76921.v2/t4

For $\Lambda_b^0\to p\pi^-\pi^+\pi^-$ decays, the CP- and P-violating observables, $a^{\hat{T}-odd}_{CP}$ and $a^{\hat{T}-odd}_{P}$, resulting from the fit to the data are...
Table 5

Data from Fig. 2a

10.17182/hepdata.76921.v2/t5

Fig2a. The invariant mass distributions for $\Lambda^0_b\to p\pi^-\pi^+\pi^-$ decays. Uncertainties on the data points are statistical only and represent one...
Table 6

Data from Fig. 2b

10.17182/hepdata.76921.v2/t6

Fig2b. The invariant mass distributions for $\Lambda^0_b\to \pi^- K^+ K^-$ decays. Uncertainties on the data points are statistical only and...

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