The quark-antiquark asymmetry of the nucleon sea from Λ and Λ fragmentation

We present a general analysis of the spin transfer for Λ and Λ production in deep-inelastic scattering of polarized charged leptons on the nucleon, and find that the pattern of different behaviors of Λ and Λ production observed by the E665 Collaboration suggests the possibility of quark-antiquark asymmetries either in the quark to Λ fragmentation functions and/or in the quark and antiquark distributions of the target proton. We also point out that the strange-antistrange asymmetry of the nucleon sea may produce an observable contribution to the different behaviors of Λ and Λ production. We find that a softer s(x) than s(x) as predicted by the light-cone baryon-meson fluctuation model of intrinsic quark-antiquark pairs of the nucleon sea might lead to a reasonable picture. However, the magnitude is still too small to explain the E665 data and the conclusion has also strong model-dependence. This may suggest the importance of quark-antiquark asymmetry in the quark to Λ fragmentation functions, provided that the E665 data are confirmed.