Search for the $Λ_b \rightarrow Λη^\prime$ and $Λ_b \rightarrow Λη$ decays with the LHCb detector

Abstract

A search is performed for the as yet unobserved baryonic $Λ_b \rightarrow Λη^\prime$ and $Λ_b \rightarrow Λη$ decays with 3$fb^{-1}$ of proton-proton collision data recorded by the LHCb experiment. The $B^0 \rightarrow K_S^0 η^\prime$ decay is used as a normalisation channel. No significant signal is observed for the $Λ_b \rightarrow Λη^\prime$ decay. An upper limit is found on the branching fraction of $\mathcal{B}(Λ_b \rightarrow Λη^\prime)<3.1\times10^{-6}$} at 90\% confidence level. Evidence is seen for the presence of the $Λ_b \rightarrow Λη$ decay at the level of $3σ$ significance, with a branching fraction $\mathcal{B}(Λ_b \rightarrow Λη)=(9.3^{+7.3}_{-5.3})\times10^{-6}$}.

22 pages, 6 figures. v2 is published version (very minor revisions)