Measurement of the asymmetry parameter for the decay $\bar\Lambda \to \bar p\pi^+$

TL;DR

This paper reports a precise measurement of the decay asymmetry parameter for the anti-Lambda particle using a large dataset from J/psi decays, providing insights into CP violation and baryon decay asymmetries.

Contribution

The study presents the first measurement of the anti-Lambda decay parameter with high statistical significance using BESII data.

Findings

Measured armbda = -0.755 b1 0.083 b1 0.063

Utilized 58 million J/psi decays and 9000 mbda b1 armbda decay events

Improved precision in decay asymmetry parameters for anti-hyperons.

Abstract

Based on a sample of $58\times10^6J/\psi$ decays collected with the BESII detector at the BEPC, the $\bar\Lambda$ decay parameter $\alpha_{\bar\Lambda}$ for $\bar\Lambda\to \bar p \pi^+$ is measured using about 9000 $J/\psi\to\Lambda\bar\Lambda\to p \bar p \pi^+\pi^-$ decays. A fit to the joint angular distributions yields $\alpha_{\bar\Lambda}(\bar\Lambda\to \bar p\pi^+)=-0.755\pm0.083\pm0.063$, where the first error is statistical, and the second systematic.