Quark Structure of $\Lambda$ from $\Lambda$-Polarization in Z Decays

TL;DR

This paper investigates the quark flavor and spin structure of the Lambda baryon using perturbative QCD and the SU(6) quark-diquark model, applying these to Lambda polarization in Z decays and comparing with experimental data.

Contribution

It compares pQCD and quark-diquark models for Lambda structure and applies them to polarization in Z decays, highlighting the models' agreement with data.

Findings

Quark-diquark model fits experimental data well.

pQCD model also fits data when accounting for helicity suppression.

Further data needed to distinguish between models.

Abstract

The flavor and spin structure for the quark distributions of the $\Lambda$-baryon is studied in a perturbative QCD (pQCD) analysis and in the SU(6) quark-diquark model, and then applied to calculate the $\Lambda$-polarization of semi-inclusive $\Lambda$ production in $e^+e^-$-annihilation near the $Z$-pole. It is found that the quark-diquark model gives very good description of the available experimental data. The pQCD model can also give good description of the data by taking into account the suppression of quark helicities compared to the naive SU(6) quark model spin distributions. Further information is required for a clean distinction between different predictions concerning the flavor and spin structure of the $\Lambda$.