Measurement of the Branching Fraction and Lambda-bar Polarization in B0 -> Lambda-bar p pi-

TL;DR

This paper reports a precise measurement of the B0 decay to Lambda-bar p pi- including its branching fraction, differential spectrum, and Lambda-bar polarization, providing insights into baryonic B decays and polarization phenomena.

Contribution

It presents the first measurement of the B0 --> Lambda-bar p pi- branching fraction and studies Lambda-bar polarization, with detailed spectral analysis using a large data sample.

Findings

Branching fraction measured as (3.07 ± 0.31 (stat) ± 0.23 (syst)) x 10^{-6}

Observation of near-threshold enhancement in the invariant mass spectrum

Lambda-bar polarization consistent with theoretical expectations at high energies

Abstract

We present a measurement of the B0 --> Lambda-bar p pi- branching fraction performed using the BaBar detector at the PEP-II asymmetric e+e- collider. Based on a sample of 467 million BB-bar pairs we measure B(B0 --> Lambda-bar p pi-) = [3.07 pm 0.31 (stat.) pm 0.23 (syst.)] x 10^{-6}. The measured differential spectrum as a function of the dibaryon invariant mass m(Lambda p) shows a near-threshold enhancement similar to that observed in other baryonic B decays. We study the Lambda-bar polarization as a function of Lambda-bar energy in the B0 rest frame (E*_Lambda) and compare it with theoretical expectations of fully longitudinally right-polarized Lambda-bar at large E*_Lambda.