Up and down quark contributions to spin content of Λ from fragmentation

We check the u and d quark contributions to the spin content of the Lambda by means of the q --> Lambda fragmentation and find that the u and d quarks of the Lambda are likely positively polarized. The parton distributions in the Lambda are given by a successful statistical model which can reproduce and correlate a vast body of polarized and unpolarized structure function and parton distribution data of the nucleon. With the Gribov-Lipatov relation between the quark distributions and fragmentation functions, the longitudinal spin transfer for the Lambda production in the polarized charged lepton deep inelastic scattering (DIS) process and the Lambda -polarization in the neutrino (antineutrino) DIS process are predicted. The available experimental data suggests that the u and d quark contributions to the spin of the Lambda are positive. In addition, our results provide a collateral evidence for the SU(3) symmetry breaking in hyperon semileptonic decays of the octet baryons, which is very important for a deeper understanding of the proton 'spin crisis'. (C) 2001 Published by Elsevier Science B.V.