Abstract
A search is performed for the charmless three-body decays of the $\Lambda_b^0$ and $\Xi_b^0$ baryons to the final states $\Lambda h^+h^{\prime -}$, where $h^{(\prime)} = \pi$ or $K$. The analysis is based on a data sample, corresponding to an integrated luminosity of $3 \rm fb^{-1}$ of $pp$ collisions, collected by the LHCb experiment. The $\Lambda_b^0 \to \Lambda K^+\pi^-$ and $\Lambda_b^0 \to \Lambda K^+K^-$ decays are observed for the first time and their branching fractions and $CP$ asymmetry parameters are measured. Evidence is seen for the $\Lambda_b^0 \to \Lambda \pi^+\pi^-$ decay and limits are set on the branching fractions of $\Xi_b^0$ baryon decays to the $\Lambda h^+h^{\prime -}$ final states.
Highlights
Separately: transitions involving a Λ+c → Λπ+ decay are used as a control sample and to normalise the measured branching fractions, and those with Λ+c → ΛK+ decays provide cross-checks of the analysis procedure
Evidence is seen for the Λ0b → Λπ+π− decay and limits are set on the branching fractions of Ξb0 baryon decays to the Λh+h − final states
Using a data sample collected by the LHCb experiment corresponding to an integrated luminosity of 3 fb−1 of high-energy pp collisions, a search for charmless three-body decays of b baryons to the Λπ+π−, ΛK±π∓ and ΛK+K− final states has been performed
Summary
The analysis is based on pp collision data collected with the LHCb detector, corresponding to 1.0 fb−1 at a centre of mass energy of 7 TeV in 2011, and 2.0 fb−1 at a centre of mass energy of 8 TeV in 2012. The online event selection is performed by a trigger [27, 28], which consists of a hardware stage, based on information from the calorimeter and muon systems, followed by a software stage, in which all charged particles with pT > 500 (300) MeV/c are reconstructed. The efficiency with which the software trigger selected the signal modes varied during the data-taking period, for reasons that are related to the reconstruction of the long-lived Λ baryon. Such decays are reconstructed in two different categories, the first involving Λ particles that decay early enough for the produced particles to be reconstructed in the vertex detector, and the second containing Λ baryons that decay later such that track segments cannot be formed in the vertex detector. The interaction of the generated particles with the detector, and its response, are implemented using the Geant toolkit [35, 36] as described in ref. [37]
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