$\Lambda, \bar{\Lambda}$ polarization and spin transfer in lepton deep-inelastic scattering

Abstract.

The flavor and helicity distributions of the $\Lambda$ and $\bar{\Lambda}$ hyperons for both valence and sea quarks are calculated in a perturbative QCD (pQCD) based model. We relate these quark distributions to the fragmentation functions of $\Lambda$ and $\bar{\Lambda}$, and calculate the z-dependence of the longitudinal spin transfer to $\Lambda$ and $\bar{\Lambda}$ in lepton deep-inelastic scattering (DIS). It is shown that the spin transfer to the $\Lambda$ is compatible with the first HERMES results at DESY, and further tests are suggested. We also make predictions for the z-dependence of the $\Lambda$ and $\bar{\Lambda}$ longitudinal polarizations in neutrino (antineutrino) DIS processes. We investigate the sea contribution to the fragmentation functions, and we test a possible scenario where the sea quarks in $\Lambda$ (or the sea antiquarks in $\bar{\Lambda}$) are negatively polarized, whereas the sea antiquarks in the $\Lambda$ (or the sea quarks in $\bar{\Lambda}$) are positively polarized. The asymmetry of the polarized fragmentation functions of the sea quarks and antiquarks to $\Lambda$ and $\bar{\Lambda}$ provides a way to understand the different behavior between the $\Lambda$ and $\bar{\Lambda}$ spin transfers observed in the recent E665 experiment at FNAL.