Ratio of $\bar{\Lambda}/\Lambda$ in Semi-inclusive Electroproduction
  It is shown that the $\bar{\Lambda}/\Lambda$ cross section ratio in semi-inclusive electroproduction of $\Lambda$ and $\bar{\Lambda}$ hyperons in deep inelastic scattering of charged lepton on a nucleon target, can provide useful information on the quark to $\Lambda$ fragmentation functions. This ratio is calculated explicitly in a quark-diquark model, a pQCD based analysis, and an SU(3) symmetry model, with three different options for the contribution from the unfavored fragmentation functions. The $x$-dependence of this ratio is sensitive to the ratio of unfavored fragmentation functions over favored fragmentation functions, $D_{\bar{u}}^{\Lambda}(z)/D_{u}^{\Lambda}(z)$, whereas the $z$-dependence is sensitive to the flavor structure of the fragmentation functions, i.e., the ratio $D_u^{\Lambda}(z)/D_s^{\Lambda}(z)$. Future measurements by the HERMES Collaboration at DESY can discriminate between various cases. 
Bo-Qiang Ma, Ivan Schmidt, Jian-Jun Yang