Polarization of Lambda0 and antiLambda0 inclusively produced by 610GeV/c Sigma- and 525GeV/c proton beams

We have measured the polarization of Lambda0 and antiLambda0 inclusively produced by 610GeV/c Sigma- and 525GeV/c proton beams in the experiment SELEX during the 1996/7 fixed target run at Fermilab. The polarization was measured as a function of the Lambda longitudinal momentum fraction xF and transverse momentum pt. For the Lambda0 produced by Sigma- the polarization is increasing with xF, from slightly negative at x_F~0 to about 15% at large xF; it shows a non-monotonic behavior as a function of pt. For the proton beam, the Lambda0 polarization is negative and decreasing as a function of xF and pt. The antiLambda0 polarization is compatible with 0 for both beam particles over the full kinematic range. The target dependence was examined but no statistically significant difference was found.