Longitudinal Spin Transfer of Λ and Λ-bar Hyperons in Polarized Proton-Proton Collisions at √(s) = 200 GeV

The longitudinal spin transfer DLL of Λ and Λ-bar hyperons produced with large transverse momenta PT in polarized proton-proton collisions is sensitive to the helicity distribution functions of strange quarks and anti-quarks, and to polarized fragmentation functions. This contribution reports a measurement of the longitudinal spin transfer DLL in the inclusive production of Λ and Λ-bar hyperons at central rapidities in polarized proton-proton collisions at a center of mass energy of √(s) = 200 GeV. The data were collected with the STAR experiment at RHIC and correspond to a ≅3 pb-1 luminosity and a ≅50% beam polarization.