Longitudinal Polarization of Lambda and anti-Lambda Hyperons in Lepton-Nucleon Deep-Inelastic Scattering

Abstract

We consider models for the spin transfers to $\Lambda$ and $\bar{\Lambda}$ hyperons produced in lepton-nucleon deep-inelastic scattering. We make predictions for longitudinal $\Lambda$ and $\bar{\Lambda}$ spin transfers for the COMPASS experiment and for HERA, and for the spin transfer to $\Lambda$ hyperons produced at JLAB. We demonstrate that accurate measurements of the spin transfers to $\Lambda$ and $\bar{\Lambda}$ hyperons with COMPASS kinematics have the potential to probe the intrinsic strangeness in the nucleon. We show that a measurement of $\bar{\Lambda}$ polarisation could provide a clean probe of the spin transfer from $\bar{s}$ quarks and provides a new possibility to measure the antistrange quark distribution function. COMPASS data in a domain of x that has not been studied previously will provide valuable extra information to fix models for the nucleon spin structure. The spin transfer to $\bar{\Lambda}$ hyperons, which could be measured by the COMPASS experiment, would provide a new tool to distinguish between the SU(6) and Burkardt-Jaffe (BJ) models for baryon spin structure. In the case of the HERA electron-proton collider experiments with longitudinally-polarised electrons, the separation between the target and current fragmentation mechanisms is more clear. It provides a complementary probe of the strange quark distribution and helps distinguish between the SU(6) and BJ models for the $\Lambda$ and $\bar{\Lambda}$ spin structure. Finally, we show that the spin transfer to $\Lambda$ hyperons measured in a JLAB experiment would be dominated by the spin transfer of the intrinsic polarised-strangeness in the remnant nucleon, providing an independent way to check our model predictions.