First observation of $\Lambda_b^0 \rightarrow \Lambda K^+\pi^-$ and $\Lambda_b^0 \rightarrow \Lambda K^+K^-$ decays at LHCb

TL;DR

This paper reports the first observation of specific $ ext{Lambda}_b^0$ baryon decays at LHCb, measuring their branching fractions and $C ext{P}$ asymmetries, contributing to understanding $b$-baryon decay properties.

Contribution

It presents the first observation of $ ext{Lambda}_b^0 ightarrow ext{Lambda} K^+ ext{pi}^-$ and $ ext{Lambda}_b^0 ightarrow ext{Lambda} K^+K^-$ decays, with measurements of their branching fractions and $C ext{P}$ asymmetries.

Findings

Decays observed at significance levels of 8.1 and 15.8 sigma.

Branching fractions measured for the observed decays.

$C ext{P}$ asymmetries found to be consistent with zero.

Abstract

The physics potential for $b$-baryon decays has been relatively unexplored until the advent of the LHC, and as such important questions still exist about their fundamental properties, such as whether their decays exhibit $C\!P$ violation. Presented here are observations of the decays $\Lambda_b^0 \rightarrow \Lambda K^+\pi^-$ and $\Lambda_b^0 \rightarrow \Lambda K^+K^-$, made at a significance level of 8.1 and 15.8 Gaussian standard deviations, respectively, and measurements of their branching fractions. The phase-space integrated $C\!P$ asymmetries of these decays are also measured and found to be consistent with zero. Limits are set on the branching fractions of other $\Lambda_b^0$ and $\Xi_b^0$ decays to $\Lambda h^+h^{\prime -}$ (where $h$ is a kaon or pion).