Observation of B_s16 to p Lambdabar pi_s16 pi- at Belle

Abstract

We study charmless $B^_s16$ meson decays to the $p bar{Lambda} pi^_s16 pi^-$ final state using a $605 {rm fb}^{-1}$ data sample collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^_s16 e^-$ collider. There are significant signals found with the $pbar{Lambda}$ mass peaking near threshold. The observed branching fraction for non-resonant $ B^_s16 to p barLambda} pi^_s16 pi^-$ is $(5.92^{_s160.88}_{-0.84} (stat.) pm 0.69 (syst.)) times 10^{-6}$ with a significance of 9.1 standard deviations. We also observe the intermediate three-body decay $B^_s16 to p bar{Lambda} rho^0$ with a branching fraction of $(4.78^{_s160.67}_{-0.64} (stat.) pm 0.60 (syst.)) times 10^{-6}$ and a significance of 9.5 standard deviations, and find a hint of a $B^_s16 to p bar{Lambda} f_2(1270)$ signal. No other intermediate three-body decay is found in this study.