Longitudinal Spin Transfer of Hyperons in Polarized Proton-Proton Collisions

We report on measurements of the longitudinal spin transfer $D_ {LL}$ in the inclusive production of $\Lambda$ and $\bar{ \Lambda}$ hyperons in 200\,GeV longitudinally polarized proton- proton collisions. At large transverse momenta $D_{LL}$ is sensitive to the helicity distributions of strange quarks and anti-quarks in the polarized proton, and to polarized fragmentation functions. The data were collected with the Solenoid Tracker At RHIC (STAR) in 2005 and correspond to a sampled integrated luminosity of $\sim\!3\mathrm{pb}^{-1}$ and $\sim\!50\%$ beam polarization. Preliminary results on $D_{LL}$, covering mid-rapidity and transverse hyperon momenta up to 4 GeV/c, will be presented and followed by an outlook on future hyperon spin transfer measurements.