Longitudinal Spin Transfer to the $\Lambda$ and $\bar{\Lambda}$ Hyperons in Muon-Nucleon Deep-Inelastic Scattering

The longitudinal polarisation transfer from muons to $\Lambda$ and $\bar{\Lambda}$ hyperons, $D^{\Lambda(\bar{\Lambda})}_{LL}$, has been studied in deep inelastic scattering off an unpolarised isoscalar target at the COMPASS experiment at CERN. The spin transfers to $\Lambda$ and $\bar{\Lambda}$ produced in the current fragmentation region exhibit different behaviours as a function of $x$ and $x_{F}$ . The measured $x$ and $x_{F}$ dependences of $D^{\Lambda}_{LL}$ are compatible with zero, while $D^{\bar{\Lambda}}_{LL}$ tends to increase with $x_{F}$ .