2018 Impact factor 4.843
Particles and Fields
Eur. Phys. J. C 16, 657-664
DOI 10.1007/s100520000447

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

B.-Q. Ma1,2,3 - I. Schmidt4 - J. Soffer5 - J.-J. Yang4,6

1 Department of Physics, Peking University, Beijing 100871, P.R. China
2 CCAST (World Laboratory), P.O. Box 8730, Beijing 100080, P.R. China
3 Institute of High Energy Physics, Academia Sinica, P.O. Box 918(4), Beijing 100039, P.R. China
4 Departamento de Física, Universidad Técnica Federico Santa María, Casilla 110-V, Valparaíso, Chile
5 Centre de Physique Th $\acute{\rm {e}}$orique, CNRS, Luminy Case 907, 13288 Marseille Cedex 9, France
6 Department of Physics, Nanjing Normal University, Nanjing 210097, P.R. China

Received: 5 April 2000 / Published online: 26 July 2000 - © Springer-Verlag 2000

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.


Copyright Società Italiana di Fisica, Springer-Verlag 2000