Measurement of matter-antimatter differences in beauty baryon decays

TL;DR

This paper reports the first evidence of $C extit{P}$ violation in baryon decays, specifically in $ extLambda^0_b$ decays to $p extpi^- extpi^+ extpi^-$, using LHCb data, with a significance of 3.3 standard deviations.

Contribution

It provides the first experimental evidence of $C extit{P}$ violation in baryon decays, expanding the understanding of matter-antimatter asymmetries beyond mesons.

Findings

Evidence for $C extit{P}$ violation in $ extLambda^0_b$ decays

Significance of 3.3 standard deviations

First such evidence in the baryon sector

Abstract

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 $C\!P$ violation. Using data from the LHCb experiment at the Large Hadron Collider, a search is made for $C\!P$-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 $C\!P$ violation both within and beyond the Standard Model of particle physics. We find evidence for $C\!P$ 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 $C\!P$ violation in the baryon sector.