First measurement of transferred polarization in the exclusive polarized-e p ---> e-prime K+ polarized-Lambda reaction

The first measurements of the transferred polarization for the exclusive ep - e'K + Λ reaction have been performed at Jefferson Laboratory using the CLAS spectrometer. A 2.567 GeV beam was used to measure the hyperon polarization over Q 2 from 0.3 to 1.5 (GeV/c), W from 1.6 to 2.15 GeV, and over the full K + center-of-mass angular range. Comparison with predictions of hadrodynamic models indicates strong sensitivity to the underlying resonance contributions. A nonrelativistic quark-model interpretation of our data suggests that the ss quark pair is produced with spins predominantly antialigned. Implications for the validity of the most widely used quark-pair creation operator are discussed.