Structure and Production of Lambda Baryons

TL;DR

This paper analyzes the quark structure and fragmentation processes of Lambda baryons, highlighting symmetry breaking effects and predicting positive polarization in experiments, with implications for understanding baryon production.

Contribution

It introduces a model incorporating hyperfine interactions that explains symmetry breaking and predicts Lambda polarization in semi-inclusive DIS.

Findings

Good agreement with measured fragmentation observables

Predicts positive Lambda polarization in DIS experiments

Explains the mass dependence of the fragmentation spectrum

Abstract

We discuss the quark parton structure of the $\Lambda$ baryon and the fragmentation of quarks into $\Lambda$ baryons. We show that the hyperfine interaction, responsible for the $\Delta$-$N$ and $\Sigma^0$-$\Lambda$ mass splittings, leads not only to sizeable SU(3) and SU(6) symmetry breaking in the quark distributions of the $\Lambda$, but also to significant polarized non-strange quark distributions. The same arguments suggest flavor asymmetric quark fragmentation functions and non-zero polarized non-strange quark fragmentation functions. The calculated fragmentation functions give a good description of all measured observables. We predict significant positive $\Lambda$ polarization in semi-inclusive DIS experiments while models based on SU(3) flavor symmetry predict zero or negative $\Lambda$ polarization. Our approach also provides a natural explanation for the dependence of the maximum of the $\xi=\ln(1/z)$ spectrum on the mass of the particles produced in $e^+e^-$ annihilation.