Observation of a Difference between Polarization and Analyzing Power in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>Λ</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>Production with 6-GeV/<i>c</i>Polarized Protons

We have measured the polarization, analyzing power, and depolarization parameter for forward ${\ensuremath{\Lambda}}^{0}'\mathrm{s}$ produced with a 6-GeV/c polarized-proton beam at the Argonne National Laboratory zero-gradient synchrotron. We collected a sample of 15 281 ${\ensuremath{\Lambda}}^{0}$ production events with subsequent $p{\ensuremath{\pi}}^{\ensuremath{-}}$ decays. There is a clear difference between the polarization and analyzing power for events with Feynman scaling variable $x$ greater than 0.8. This is the first observation of this phenomenon at high energy.