Up and Down Quark Contributions to Spin Content of Lambda from Fragmentation

Abstract

We check the $u$ and $d$ quark contributions to the spin content of the $Λ$ by means of the $q\toΛ$ fragmentation and find that the $u$ and $d$ quarks of the $Λ$ are likely positively polarized. The parton distributions in the $Λ$ 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 $Λ$ production in the polarized charged lepton deep inelastic scattering (DIS) process and the $Λ$-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 $Λ$ 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'.