Observation of B+ to p Lambdabar pi+ pi- at Belle

TL;DR

This paper reports the observation of specific charmless B+ meson decays to p Lambda-bar pi+ pi- final states, measuring their branching fractions and identifying intermediate resonances using data from the Belle detector.

Contribution

First observation of B+ to p Lambda-bar pi+ pi- decays with measured branching fractions and identification of intermediate resonant states.

Findings

Significant signals for B+ to p Lambda-bar pi+ pi- and B+ to p Lambda-bar rho^0 decays.

Measured branching fractions: (5.92±0.88(stat)±0.69(syst))×10^{-6} and (4.78±0.67(stat)±0.60(syst))×10^{-6}.

Evidence for B+ to p Lambda-bar f_2(1270) decay.

Abstract

We study charmless $B^+$ meson decays to the $p \bar{\Lambda} \pi^+ \pi^-$ 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 $e^+ e^-$ collider. There are significant signals found with the $p\bar{\Lambda}$ mass peaking near threshold. The observed branching fraction for non-resonant $ B^+ \to p \bar\Lambda} \pi^+ \pi^-$ is $(5.92^{+0.88}_{-0.84} (stat.) \pm 0.69 (syst.)) \times 10^{-6}$ with a significance of 9.1 standard deviations. We also observe the intermediate three-body decay $B^+ \to p \bar{\Lambda} \rho^0$ with a branching fraction of $(4.78^{+0.67}_{-0.64} (stat.) \pm 0.60 (syst.)) \times 10^{-6}$ and a significance of 9.5 standard deviations, and find a hint of a $B^+ \to p \bar{\Lambda} f_2(1270)$ signal. No other intermediate three-body decay is found in this study.