A study of the polarization of Lambda hyperons produced in inelastic pN rea
ctions induced by the 450 CeV proton beam from the CERN SPS has been perfor
med with the NA48 detector. The Lambda hyperons were detected at a fixed an
gle of 4.2 mrad in the momentum range from 50 GeV/c to 200 GeV/c. The polar
ization changes from -0.053 +/- 0.034 to -0.298 +/- 0.074 for a transverse
momentum range of the Lambda between 0.28 GeV/c and 0.86 GeV/c. The <(Lambd
a)over bar> polarization is consistent with zero.