Observation of a Difference between Polarization and Analyzing Power inΛ0Production with 6-GeV/cPolarized Protons

Abstract

We have measured the polarization, analyzing power, and depolarization parameter for forward ${\Lambda }^0\text{'}\mathrm{s}$ produced with a 6-GeV/c polarized-proton beam at the Argonne National Laboratory zero-gradient synchrotron. We collected a sample of 15 281 ${\Lambda }^0$ production events with subsequent $p{\pi }^{-}$ 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.