Abstract
We study the charmless two-body Λ <sub>b</sub> → Λ (ϕ, η <sup>(′)</sup> ) and three-body Λ <sub>b</sub> → Λ K <sup>+</sup> K <sup>-</sup> decays. We obtain B(Λ <sub>b</sub> → Λ ϕ) = (3.53 ± 0.24) × 10 <sup>- 6</sup> to agree with the recent LHCb measurement. However, we find that B(Λ <sub>b</sub> → Λ (ϕ→) K <sup>+</sup> K <sup>-</sup> ) = (1.71 ± 0.12) × 10 <sup>- 6</sup> is unable to explain the LHCb observation of B(Λ <sub>b</sub> → Λ K <sup>+</sup> K <sup>-</sup> ) = (15.9 ± 1.2 ± 1.2 ± 2.0) × 10 <sup>- 6</sup> , which implies the possibility for other contributions, such as that from the resonant Λb→K-N∗,N∗→ΛK+ decay with N <sup>∗</sup> as a higher-wave baryon state. For Λ <sub>b</sub> → Λ η <sup>(′)</sup> , we show that B(Λb→Λη,Λη′)=(1.47±0.35,1.83±0.58)×10-6, which are consistent with the current data of (9.3-5.3+7.3,<3.1)×10-6, respectively. Our results also support the relation of B(Λ <sub>b</sub> → Λ η) ≃ B(Λ <sub>b</sub> → Λ η <sup>′</sup> ) , given by the previous study.