A Study of the Polarization of Lambda Hyperons in Hadronic Z0 Decays

We present a preliminary study of the polarization of Lambda^0 hyperons
produced in hadronic jets, along their flight direction and transverse to the
plane defined by the initial quark direction and the Lambda momentum. We used a
sample of 550,000 hadronic decays of polarized Z0 bosons collected by the SLD
experiment at the SLC. The high longitudinal electron beam polarization allowed
the determination of the quark (rather than antiquark) direction with high
purity.  The Lambda^0 -> p pi^- decay mode was reconstructed, and the transverse
polarization studied as a function of its momentum and momentum transverse to
the thrust axis.  An upper limit on such polarization is presented.  The
predictions of fragmentation models are discussed.