Study of $\itΛ_{\it{b}}^\rm{0}$ and $\itΞ_{\it{b}}^\rm{0}$ decays to $\hat{I}›h^{+}{h}^{{}^{\prime }-}$ and evidence for $CP$ violation in $\itΛ_{\it{b}}^\rm{0}\to\itΛ K^+K^-$ decays

Abstract

A study of $\itΛ_{\it{b}}^\rm{0}$ and $\itΞ_{\it{b}}^\rm{0}$ decays to $\hat{I}›h^{+}{h}^{\prime -}$ $(h^{(\prime )}=\ddot{I}€,K)$ is performed using $pp$ collision data collected by the LHCb experiment during LHC Runs 1$-$2, corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$. The branching fractions for these decays are measured using the $\itΛ_{\it{b}}^\rm{0}\to\itΛ_{\it{c}}^+(\to\itΛπ^+)π^-$ decay as control channel. The decays $\itΛ_{\it{b}}^\rm{0}\to\itΛπ^+π^-$ and $\itΞ_{\it{b}}^\rm{0}\to\itΛK^-π^+$ are observed for the first time. For decay modes with sufficient signal yields, $CP$ asymmetries are measured in the full and localized regions of the final-state phase space. Evidence is found for $CP$ violation in the $\itΛ_{\it{b}}^\rm{0}\to\itΛK^+K^-$ decay, interpreted as originating primarily from an asymmetric $\itΛ_{\it{b}}^\rm{0} \to \it{N}^{*+} \it{K}^-$ decay amplitude. The measured $CP$ asymmetries for the other decays are compatible with zero.

All figures and tables, along with any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/1624/ (LHCb public pages)